Polymer Journal, Vol. 9, No. 5, pp 499-510 (1977)

Haloaldehyde Polymers. X. Poly(dibromochloroacetaldehyde)*

D. W. LIPP and 0. VooL

Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, U.S.A.

(Received April 13, 1977)

ABSTRACT: Dibromochloroacetaldehyde was synthesized in good yield from chloro­ acetaldehyde diethyl acetal by bromination. It was purified to give a monomer suitable for homo- and copolymerization. Polymerization could be carried out with anionic and cationic initiators; anionic polymerization gave good yields of a crystalline polymer which could be stabilized. Vacuum degradation of the polymer gave the monomer form quantitatively. The Tc of polymerization (IM) was -40°C. Dibromochloroacetaldehyde copolymerized with chloral and phenyl isocyanate to insoluble and infusible polymer, but was less reactive than chloral. KEY WORDS Poly(dibromochloroacetaldehyde) / Dibromochloro- acetaldehyde / Haloaldehyde Polymers / Ceiling Temperatures / Cryotachensic Polymerization /

A number of haloacetaldehydes have recently case of chloral, alkali metal alkoxides and ter­ been prepared and their polymerization behavior tiary amines, especially the heterocyclic tertiary

investigated. The most prominent of the per­ amines served as good initiators. Also SbC1 5, 1 4 halogenated acetaldehydes is chloral, - but A1Cl 3 , H 2S04 , and trifluoromethanesulfonic acid chlorofluoroacetaldehydes have also been stud­ gave the homopolymer of bromodichloroacetal­ ied. 5-s These investigations were primarily dehyde. The polymer was characterized, the carried out to determine the extent of size or rate of polymerization under anionic and cationic bulkiness of the perhalomethyl side chain on polymerization conditions investigated, and whose upper side only isotactic polymers have the ceiling temperature of polymerization deter­ been able to be prepared. The dichlorofluoro­ mined. methyl group to be the smallest group whose Copolymerization of bromodichloroacetalde­ corresponding aldehyde produces only insoluble, hyde was accomplished with chloral and with presumably isotactic polymer. Poly(chlorodi­ phenyl isocyanate and primarily with anionic fluoroacetaldehyde) also exists in a soluble initiators. (presumably atactic) and polyfluoral in a soluble The objective of this work was to synthesize elastomeric form. the previously unknown dibromochloroacetal­ Very recently it was demonstrated that bromo­ dehyde, to characterize and purify it, to study dichloroacetaldehyde could be synthesized from its homo- and copolymerization and the stability triphenylphosphine and chloral followed by of its polymers and to determine the ceiling bromination of the double bond in the dichloro­ temperature for polymerization. vinyloxyphosphonium compound.9 •10 Hydrolysis of the salt followed by careful purification gave EXPERIMENT AL polymerization-grade monomer capable of being polymerized by anionic initiators. As in the Materials * Part IX: D. W. Lipp and 0. Vogl, J. Polym. Chloroacetaldehyde diethyl acetal, phenyl iso­ Sci., Polym. Chem. Ed., in press. cyanate and n-butyl isocyanate (Aldrich Chemical

499 D. w. LIPP and 0. VOGL

Co.), were fractionated under reduced pressure 0.67 mol) was added and the assembly was placed before use. Trifluoromethanesulfonic acid (Al­ into an oil bath at l00°C. Bromine (85 ml, 1.5 drich Chemical Co.), was used in the condition mol) was added dropwise while stirring at a just as obtained. rate that just allowed the red color in the flask Pyridine, acetic andydride and nitrobenzene to vanish. This addition was complete after 8 hr. (Eastman Kodak Co.), were used from freshly The addition funnel was replaced with a ground opened bottles. Bromine and aluminum chlo­ glass stopper and the reflux condenser was re­ ride (Fisher Scientific Co.), were used directly. moved and replaced with an adapter for distil­ Aluminum chloride was handled in a dry box lation. One end of the condenser was joined filled with dry nitrogen. to an adapter and its other end to a 100-ml Chloral (Montrose Chemical Co.), was used round-bottom receiving flask with a vacuum after careful fractionation. 11 adapter, which was cooled in a dry ice-isopro­ Lithium tertiary butoxide (LTB) (Ventron Alfa panol bath. Volatile products (EtBr 95%, EtOH Products) was sublimed at 0.1 mm and 150°C 5%) were collected at a pressure of 15 mm and prior to its use. Toluene (Mallinckrodt Chem­ 40°C. The receiving flask was replaced with a ical Co.), was dried over sodium wire. 200-ml round-bottom flask. Phosphorus pent­

Triphenylphosphine (Ph3P) (Mallinckrodt oxide (5.0 g) was add.ed and the entire apparatus Chemical Co.), was used without further puri­ was purged with dry nitrogen for 5 min. The fication. Antimony pentachloride (Fisher Scien­ flow of nitrogen was lessened and the flask was tific Co.), was distilled at 75°C and 20 mm then heated with an oil bath at 150°C while through a 30-cm Vigreux column. cooling the receiving flask in a dry ice-isopro­ Measurements panol bath. After ethanol was collected up to Infrared spetra were obtained on a Perkin-Elmer a vapor temperature of 100°C, the vapor tem­ 727 infrared spectrometer at a "normal" scan perature rose rapidly. Distillation was conti­ rate or on a Beckman infrared spectrometer at nued using a dry 200-ml flask and the pressure a slow scan rate. Proton magnetic resonance (controlled by a manostat) was reduced to 100 spectra (PMR) were obtained on a Hitachi Perkin­ mm; the second fraction was impure dibromo­ Elmer R-24 spectrometer or on a 90-MHz chloroacetaldehyde. Perkin-Elmer R-32 spectrometer. The receiver was then removed from the cold DSC measurements were made under nitrogen bath and was allowed to warm to room tem­ on a Perkin-Elmer DSC-lB instrument at a scan perature under a blanket of nitrogen. The rate of 20°Cjmin. aldehyde was then redistilled from the P20 5 at TGA data were obtained on a Perkin-Elmer l00°C/30 mm under nitrogen. The first 3 ml TGS-1 thermobalance under nitrogen at a heat­ were collected and the receiver was replaced ing rate of 20°Cjmin; the heating rate was with one that had been cooled in a dry ice-iso­ regulated by a Perkin-Elmer UU-1 temperature propanol bath at - 78°C. About 30ml of color­ program control. The gas chromatograms were less liquid were collected as a middle cut. The obtained on a Varian Associates Model 920 gas aldehyde was redistilled from phosphorus pent­ chromatograph on a 2-m column packed with oxide (3.0 g) under nitrogen at 30-mm pressure 35-% diisodecyl phthalate on Chromosorb W or through a 6-inch Vigreux column. The first on a 1-m Porapak Q column. 4 ml of dibromochloroacetaldehyde were dis­ carded and then about 25 ml of pure aldehyde Procedures were collected as a colorless liquid (25.2 ml, Synthesis of Dibromochloroacetaldehyde from 38-% yield), boiling at 147-148°C (760 mm). Chloroacetaldehyde Diethyl Acetal. A 500 ml 3- The infrared spectrum (neat) showed major ab­ neck round-bottom flask was equipped with a sorptions at 1750 cm-1 (vs) (C=O stretch), 3500 pressure-equalizing addition funnel, a nitrogen cm-1 (w) (overtone); 2850 cm-1 (m), 650 cm-1 inlet tube, and a reflux condenser. The flask (s). The carbonyl stretch in hexane was 1758 was purged with dry nitrogen for 10 min and cm-1 and in the gas phase 1768 cm-1• then chloroacetaldehyde diethyl acetal (100 ml, The PMR spectrum showed one peak at o=

500 Polymer J., Vol. 9, No. 5, 1977 Haloaldehyde Polymers. X.

8.7 ppm. Anal. Calcd for C2HBr2ClO: C, 10.17; Copolymerization of DBCA and Chloral with H, 0.42; Cl, 15.01; Br, 67.66. Found: C, 10.24, AlCl3• A 12-inch long (10-mm I.D.) Pyrex tube H, 0.60; Cl, 14.59; Br, 67.39. was sealed at one end and flamed out. Freshly Polymerization of DBCA with Pyridine. A 12- distilled chloral (2 ml, 20 mmol), DBCA (2 ml, inch long (10-mm I.D.) Pyrex tube was sealed 20 mmol) and 0.1 mg of AICl 3 in nitrobenzene at one end, washed, dried and flamed out. (1-M solution of AICl3 in nitrobenzene, 0.1 Freshly distilled DBCA (2 ml, 20 mmol) was mmol, 0.5 mol%) were added with dry syringes. added followed by pyridine (0.4 ml of a 1-molar The tube was inserted in a liquid nitrogen solution in toluene, 0.4 mmol or 2 mol%); the bath, sealed at 0.1 mm, shaken at room tem­ tube was inserted in a liquid nitrogen bath, perature and then placed in a dry ice-chloro­ sealed at 0.1-mm pressure, thoroughly cooled benzene slush bath at -45°C for 24 hr; a gel to room temperature and then placed in a dry formed after 1 hr. The tube was warmed to ice-chlorobenzene slush bath at -45°C for 72 hr. room temperature, cut into several sections, A self-supporting gel formed after 10 min. The soaked in acetone (30 ml) for 24 hr and dried. polymerization was essentially complete after Chloral-DBCA copolymer was obtained as 1 hr but was allowed to proceed for 72 hr. translucent, tough cylinders in the shape of the The tube was warmed to room temperature polymerization tube (4.93 g, 66-% yield). The and was then cut into sections about 2.5-cm infrared spectrum showed absorptions at 2940 long with a glass file. The sections of tubing cm-1 (m) (C-H stretching); 1370 cm-1 (w); 1344 containing the polymer were soaked in an acetic cm-1 (m), 1320 cm-1 (s) (C-H bending); 1105 anhydride (10 ml)-acetone (10 ml) mixture for cm-1 (vs, b) 947 cm-1 (vs, b) (C-O streching); 24 hr at -10°C. The polymer was isolated, 828-805 cm-1 (s, b), 800 cm-1 (s), (C-CI stretch­ washed with acetone (50 ml), soaked for ing); 787 cm-1 (m); 750 cm-1 (s, b), 672 cm-1 24 hr in dichloromethane (20 ml) at -10°C, (m) (C-Br streching). filtered and dried. Poly-DBCA (2.37 g, 52-% Copolymerization of DBCA and Phenyl Isocya­ yield) was obtained as colorless translucent nate (10-% Isocyanate in Feed). A 12-inch long chips. The infrared spectrum (KBr) showed (10-mm I.D.) Pyrex tube was sealed on one end. absorptions at 2940 cm-1 (C-H stretching), 1370 Freshly distilled DBCA (2.0 ml, 20 mmol) and cm-1, 1338 cm-1, and 1310 cm-1 (C-H bending), phenyl isocyanate (0.2 ml, 2 mmol, 10 mol,96) 1105 cm-1, 1065 cm-1, 1040 cm-1, 950 cm-1 (vs), were added with a dry syringe, the tube was (C-O streching), 802 cm-1 (C-C streching or then shaken briefly and pyridine (0.4 ml of a C-CI stretching), 780 cm-1, and 726 cm-1 (C­ 1-M solution in toluene, 0.4 mmol, 2 mol%) halogen stretching). Anal. Calcd for C2HBr2CIO: was added carefully. The tube was inserted in C, 10.17, H, 0.42; Cl, 15.01; Br, 67.66. a liquid nitrogen bath, sealed at 0.1-mm pressure Found: C, 10.38, H, 0.69; Cl, 15.00; Br, and shaken at room temperature to mix the 67.28. reactants thoroughly. It was then placed in a Stabilization of Poly-DBCA by Treatment with dry ice-acetone bath at - 78°C, and allowed to 12 PC15 • To a dry 125-ml flask being slowly purged remain undisturbed 72 hr. After warming to room with dry nitrogen were added poly-DBCA (1.0 g) temperature, the polymerization tube was cut and PC15 (15 ml of a 1-M solution in CCl4). into several sections, soaked in acetone (25 ml) for A reflux condenser was connected to the flask 8 hr and dried. DBCA-phenyl isocyanate co­ and the flask was heated to reflux with an oil polymer was obtained as small white granules bath for 2 hr. The flask was allowed to cool; (2.51 g, 54-% yield). An infrared spectrum (KBr) the product was collected on a sintered funnel, showed absorptions at 2950 cm-1 (m), 2885 cm-1 1 rinsed with CCl4 (50 ml), and dried under nitro­ (w) (C-H stretching); 1745 cm- (vs) (C=O gen (0.89 g, 89-% yield). The infrared spectrum stretching, urethane); 1601 cm-1 (m), 1550 cm-1 of this product could be superimposed on spectra (w), 1528 cm-1 (w), 1497 cm-1 (m), 1430 cm-1 (w) for unstabilized poly-DBA. A TGA of this (aromatic); 1373 cm-1 (w), 1355 cm-1 (m), 1318 product indicated that the thermal stability was cm-1 (s) (C-H bending, acetal carbon); 1109 increased substantially by this treatment. cm-1 (vs), 1068 cm-1 (vs), 1050 cm-1 (vs), 950

Polymer J., Vol. 9, No. 5, 1977 501 D. w. LIPP and 0. VOGL cm-1 (vs) (C-O stretching); 810 cm-1 (s), 789 the NMR tube so that 6 cm of the NMR tube cm-1 (s), 752 cm-1 (s), 747 cm-1 (s), 705 cm-1 were filled with initiated monomer. The syringe (w). Anal. for N: 0.79% (12% of isocyanate needle connected to the nitrogen source was re­ in the copolymer). moved and very quickly the tube was closed Vacuum Degradation of Poly-DBCA Obtained with a pressure cap and the top of the NMR from DBCA and Pyridine. A 16-inch long Pyrex tube was wrapped with Parafilm. The NMR tube (12-mm I.D.) was bent into a U shape and tube was removed from the 50°C bath, wiped one end was sealed. DBCA powder (1.0 g) was off, and the zero time aldehyde proton (o=8.9) placed in the closed end of the U-tube, and the intensity was recorded. (The methyl group re­ tube was sealed at 0.1-mm pressure. The empty sonances of the toluene was used as an internal end of the U-tube was placed in a liquid nitrogen standard.) It was then placed in a - 78°C bath bath and the other end, containing the polymer, along with test tube which contained the remain­ in a silicone-oil bath at 180°C. After 30 min ing initiated monomer which was used as a a colorless solid had collected in the cold end control sample. The NMR tube was removed of the U-tube. No residue was detected in the from the - 78°C bath after periods of 2, 5, 10, 20, hot end in the oil bath. The tube was warmed 40, 60, 120, and 360 min and the aldehyde peak to room temperature, the colorless solid was intensity was determined by integration. An melted and the tube was cut open. A sample infrared spectrum of the control sample after of the colorless liquid was drawn out with a extraction of unreacted DBCA could be super­ 10-µl syringe and immediately injected into a imposed on previous spectra for the polymer. gas chromatograph. The remainder of the color­ Ceiling-Temperature Determination for DBCA less liquid was poured into a tared screw-cap in Toluene with Pyridine. Four polymerization bottle (0.97 g or 97%). The analysis by gas tubes were washed in 1-N HCl, rinsed with chromatography (35-% diisodecyl phthalate on distilled water four times and dried for 72 hr at Chromosorb W) indicated that the colorless liquid 120°C. One test tube was removed from the was 98-% dibromochloroacetaldehyde. An in­ oven. A syringe needle connected to a source of frared spectrum was nearly superimposable on dry nitrogen was inserted. The tube was purged a spectrum of pure DBCA. with nitrogen and then freshly distilled DBCA Polymerization Rate of DBCA at -78°C by (3.0 ml, 30 mmol) was added while the flow of NMR. NMR tubes and a 15-mm test tube were dry nitrogen was maintained. The lower half prepared for the experiment according to a con­ of the tube was cooled in liquid nitrogen. sistent cleaning procedure10 and finally dried at Toluene (2.7 ml) and pyridine (0.3 ml of a 1-M 120°C for 72 hr. The test tube was clamped in solution in toluene, 0.3 mmol, 1 mo!%) were a vertical position and the nitrogen flow was added; the tube was sealed and placed in an started through a syringe needle. The tube isopropanol bath at 50°C. The bath was was purged for 5 min, heated with an air gun, cooled at a rate of 2°Cjmin by a copper coil allowed to cool to room temperature while a with a regulated flow of cold nitrogen. The flow of nitrogen was maintained, and lowered intensity of light transmitted through the into an oil bath maintained at 25°C. Freshly sample was recorded. The flow of cold gas distilled DBCA (3 ml, 30 mmol) was added with continued until the temperature reached -60°C. a dry syringe and the temperature inside the The tube was removed from the cold bath and test tube was allowed to reach 50°C. Pyridine a self-supporting polymer gel was observed in (0.6 ml of a 1-M solution in toluene, 2 mo!%, the sealed tube. A cloud point of -10°C was 0.6 mmol) was added and the tube was agitated. recorded as the polymerization threshold tem­ The NMR tube was removed from the oven, perature at a 8.33-molar monomer concentra­ clamped in a vertical position, purged with dry tion. In separate experiments cloud points ot nitrogen for 3 min, and placed in the 50°C oil -12 °C for a 6.67-molar solution, -21 °C for bath to a depth of 7.5 cm. The initiated solu­ 5.0-molar solution and -27.5°C for a 2.5-molar tion was then transferred from the test tube to solution were recorded respectively. Infrared

502 Polymer J., Vol. 9, No. 5, 1977 Haloaldehyde Polymers. X. spectra of the tube contents in each experiment the use of sulfuric acid which is commonly indicated that poly-DBCA had been formed. needed for the decomposition of acetals. The monoethyl acetal at the end of step one was of RESULTS AND DISCUSSION good purity in the reaction flask and DBCA was obtained in good yield. DBCA was finally Dibromochloroacetaldehyde (DBCA) was ob­ purified by distillation through a spinning tained in a 50-% overall yield from chloroacetal­ band column at 100 mm and the pure product dehyde diethyl acetal and bromine. It was was analyzed by GC. At a column tempera­ purified, characterized, homopolymerized, co­ ture of 1l0°C, DBCA had a retention time of polymerized, and the characteristics of the poly­ 15 min and 42 sec on the column described in mers were determined. the Experimental Part and the total impurities Bromination of chloroacetaldehyde diethyl level was less than 0.2%. acetal had to be carried out at 100°C in a rapidly DBCA was analyzed for all elements although stirred solution in such a way that the bromine the analyses for the halogens were difficult be­ would almost immediately be discharged as it cause of the interference of the presence of a was added. If the conditions were not carried high percentage of bromine with the analysis out exactly, side reactions occurred (eq 1). for chlorine. Derivatives of this aldehyde, such H as the 2,4-dinitrophenylhydrazone and the oxime could not be prepared because they were ap­ B½ I l CICH2C(OC2Hs)2 ----> CIBr2CCOC2Hs + C2HsBr parently too unstable. I 100°c / I H OH DBCA boiled at 148°C and 760 mm and had a density at 25°C of 2.27 g/cm3 • The PMR C1Br2CCHO + C2H5OH spectrum showed a singlet at 8.70 ppm. In a ( I ) comparison, chloral, under the same conditions, The reaction product of the bromination is showed a singlet at 8.95 ppm. The 13C NMR actually DBCA monoethyl acetal which was spectrum shows a chemical shift of 176.3 ppm thermally decomposed at 150°C to give DBCA for a carbonyl carbon and 63.7 ppm for the tri­ and ethanol. DBCA monoethyl acetal was iso­ halomethyl carbon, downfield from TMS. The lated and purified by fractional distillation at infrared spectrum of DBCA is shown in Figure reduced pressure at a temperature well below 1. It showed characteristic aldehyde carbonyl the decomposition point. The PMR spectrum stretching assignments at 1768 cm-1 in the gas and elemental analyses confirmed this structure. phase, 1758 cm-1 in n-hexane and 1750 cm-1 neat. The decomposition of the hemiacetal was more The comparative values for chloral are 1776 conveniently carried out thermally without cm-1, 1768cm-1, and 1760cm-1•

100

i 80

20

0 '----:3::--:5~0"'0----:2:--:s,":,o-=-o----2.,..0""0""0____ 15_.,0_0 ____ 12..... o_o ____ s_.o .... o--

Frequencv ( cm- 1 ) Figure 1. IR spectrum of DBCA (neat).

Polymer J., Vol. 9, No. 5, 1977 503 D. W. LIPP and 0. VoaL

Polymerization H DBCA could be homopolymerized in the pre­ Re I Br2CCICHO ------> +c-O--h ( 2) sence of a variety of nucleophiles and some REB I selected acids as can be seen in Table I. The CICBr2 reaction times in this table are neither the maxi­ Protic acids such as sulfuric acid and also mum nor optimum reaction times but rather trifluoromethanesulfonic (triflic) acid were poor reaction times following which no more poly­ initiators and probably were occluded in the merization visibly occurred. Though very rare polymer as it precipitated during the early part in the case of high-yield reactions, the poly­ of the polymerization and further polymerization merization was over within the first 2 or 3 hr as was prevented. A long induction period was was later shown in the NMR rate studies of the required before any polymer precipitated. The DBCA polymerization. It may be seen that at bulky side group may have influenced this reac­ -45°C, pyridine, quinoline, and LTB as well as tion. cesium chloride and cesium fluoride were good All polymerizations were initiated above the initiators. This confirmed our earlier findings polymerization threshold temperature (cryo­ for perhaloacetaldehyde polymerizations where tachensic polymerization). The yield of poly­ amines and halide ions, particularly fluoride and mers after extraction with acetone or dichloro­ chloride, were excellent initiators. It was im­ methane was about 50%. The monomer, which portant that the temperature be kept at -45°C, was held firmly by the polymer, was extracted, for a high yield polymerization. This tempera­ and during the extraction an unstable fraction ture was most conveniently maintained by a was degraded to the monomer; yields before dry ice-chlorobenzene slush bath. extraction were probably about 20% higher. Most of the nucleophiles which polymerized Table I. Bulk polymerization of DBCA• chloral and BOCA also polymerized DBCA with the important exceptions of bromide and Initiator Reaction time Yield,% iodide salts. When Ph 3P was used for the poly­ Pyridine 72hr 52 merization of DBCA, no polymer was obtained Quinoline 72hr 47 but polymerization occurred readily with the

LTB 72hr 30 phosphonium salt from Ph3P and chloral. It

SbCl5 1 week 24 was possible for the reaction of Ph3P with DBCA, H2SO4b 1 month 3 to take place in two different ways to give H2SO4 1 week 4 either I or II (eq 3). CFaSOsH 0 1 month 3 CsCI 72hr 44 H Bre CsF 72hr 49 I EB AlCls/CsH5NO2 72hr 38 R 3P + Br2CCICHO ---. C!BrC=C-O-PR3 I (C2H5)4NEBC!e 72hr 39 EB Br2C=C-O-PR2 II Ph3P+O-CH=CC12 72hr 35 I C!B ere H • Initiator concentration, 2 mo!%; polymerization H bath temperature, -45°C. H 2o I Phosphonium salt ------> RsP--->O + C!BrCCHO b Polymerization bath temperature, -20°C. I + HBr c Polymerization bath temperature, - 78°C. H H2o I With anionic initiators, higher yields were Phosphonium salt ------> Br2CCHO + HCI ( 3 ) obtained and the polymers, as in other cases of II perhaloacetaldehyde polymers, were hard homo­ geneous gels. SbCl5 and aluminum chloride were The only reaction observed at 25°C was the also reasonably good initiators for this poly­ removal of a bromine ion. The salt I was merization (eq 2). identified, by analysis of chlorobromoacetalde-

504 Polymer J., Vol. 9, No. 5, 1977 Haloaldehyde Polymers. X. hyde, as its hydrolysis product. Dibromoacetal­ trifluoromethanesulfonic acid even after long dehyde was not detected. The salt I was iso­ reaction times; the yields of poly-DBCA were lated and the structure confirmed by elemental the same regardless of whether the polymeri­ analysis. This bromide salt was not the initia­ zation was carried out at -20°C or - 78°C, tor for the DBCA polymerization. The chloral­ namely 3%. The polymerizations of DBCA triphenylphosphine (1 : 1) salt is a phosphonium initiated with antimony pentachloride and alumi­ chloride and neither did it nor did the bromal­ num chloride gave higher yields; they were triphenylphosphine (1 : 1) salt initiate DBCA nearly the same as those of the anionic poly­ polymerization. However, cesium chloride was merizations. a good initiator though cesium bromide was Poly-DBCA shows an infrared spectrum which not under the reaction conditions. Thus the is fairly similar to that of other haloacetaldehyde chloride ion was a good initiator for DBCA polymers, particularly polychloral. A structure but not the bromide ion. of a substituted polyacetal is indicated. Major The yield and reaction rate of the polymeri­ absorptions of the IR spectra are shown in zation of DBCA in the presence of acids, or Table II and the spectrum is displayed in generally cationic initiators, were markedly lower Figure 3. Only in the case of cationically pre­ than in the polymerization of chloral and BDCA. pared polymers were any OH end groups notice­ Particularly surprising were the low yields of able. Strong absprptions were in the region of polymers obtained from sulfuric acid and the ether oxygen and carbon-halogen bonds

100

80 #. a, u .i 60 E U1 40 CICBr2 COOCH 2 CICBr2 (KBr) i-=

20

o---:::~~--~~------:~~--....,..,=---..,...,,..=----~--3500 2800 2000 1600 1200 800

Frequency ( cm- 1 ) Figure 2. IR spectrum of dibromochloroethyl dibromochloroacetate (KBr pellet).

Br2 CCICHO Polymer (KBr) 100

~80 a, u 60 .E

C 40 C1l t-= 20

0'---:::3-='50"'0:c----,2:-::s~o"""o--2"'0~0'""0:---:-1-='5"'"00=---1...,2'"'0-o___ s,....o-o--

Frequency (cm- 1 ) Figure 3. IR spectrum (KBr pellet) of poly-DBCA.

Polymer J., Vol. 9, No. 5, 1977 505 D. W. LIPP and 0. VoGL

Table II. Major absorptions in infrared spectra Table IV. DTG maxima of degradation rate of of homopolymers of DBCA and chloral DBCA homo- and DBCA-chloral copolymers• in cm-1 (±2 cm-1) Initiator for polymer Maximum temp, oc Poly-DBCA Polychloral preparation 1372 1386 Homopolymers 1348 1360 Pyridine 120 1320 1325 Pyridine, PCls treated 255 280 1115 1122 H2SO4 238 280 1075 1085 CF3SO3H 249 1040 1075 SbCls 300 943 975 Copolymers Pyridine 125 CF3SO3H 250 Tabel III. Wide angle X-ray studies. Interplanar spacings of poly-DBCA (in A.) • Heating rate 20°C/min, in nitrogen

Poly-DBCA Polychloral initiators such as pyridine and showed a maxi­ mum rate of degradation at 120°C. This in­ Spacing Approx. Spacing Approx. intensity intensity stability is apparently caused by one unstable 8.90 100 8.70 100 end group in the polymer which is believed 5.10 90 5.00 90 to be an occluded active alkoxide end. Cation­ 3.40 60 3.30 80 ically prepared poly-DBCA was much more 2.80 50 2.73 50 stable and usually showed two maxima, one 2.30 40 2.40 40 around 250°C and one near 300°C. ------The polymer prepared with pyridine as the in the region of 1150 and 600 cm-1. The carbon­ initiator, which had a maximum of only 120°C, PC1 6 • hydrogen stretching frequency in all cases was could be stabilized by treatment with Maxima of degradation rates were found at 255 near 2940 cm -i. polymer. During Samples of poly-DBCA gave Debye-Scherrer and 280°C, for the stabilized in the polymer had diagram which indicated it to be a semicrystal­ this treatment the bromine the IR spectra of line polymer with interplanar spacings similar not been replaced because were superimposable on those to that for polychloral; the prominent lines are these polymers PC1 5 treatment. Also, the elemental shown in Table III. A slight increase in the taken before no halogen exchange. spacings of poly-DBCA as compared to that of analysis indicated polychloral and poly-BDCA indicates the increas­ H H I J I ing bulk of the side chain, and consequently an +C-O--1;,----> nC=O (4) increase of the interchain distances. I I Br2CCl ClCBr2 Poly-DBCA prepared with pyridine as the initiator was degraded in a sealed evacuated Copolymerizations tube and the volatile materials collected. Degra­ DBCA could be copolymerized with other dation occurred at 180°C to give a 98-% yield haloaldehydes, primarily chloral (Table V) or of a liquid which proved to be 98 % pure with phenyl isocyanate (Table VI). DBCA. When the degradation of various sam­ Br2CCl I~ H O -I was carried out in a TGA I I II ples of poly-DBCA C=O + RN=C=O -l---f-C-O-0,.C-N-- apparatus and the thermal degradation spectrum recorded, three regions of stability of these k __ Br2tc1 i _lz DBCA polymers were obtained, depending upon ( 5) the initiators used for the polymerization as Table V shows the results of some copoly­ shown in Table IV. Polymers which were merizations of DBCA with chloral in the presence very unstable were usually prepared by anionic of pyridine and CF3SO3H. It was shown that

506 Polymer J., Vol. 9, No. 5, 1977 Haloaldehyde Polymers. X.

Table V. Preparation of DBCA-chloral copolymers•

Chloral in Polymerization Polymerization Polymerization Conversion, DBCA in bath temperature, feed, 96 initiator oc time, hr % product, 96 75 Pyridine -45 3 57 3 75 Pyridine -45 3 63 10 25 Pyridine -45 3 50 28 75h Pyridine -78 3 62 5 50b Pyridine -78 3 55 12 25h Pyridine -78 3 27 28

75 CFaSOaH -10 320 44 11 50 CFaSOaH -10 320 41 27 25 CFaSOaH -10 320 36 40 • Initiator concentration (2 mol%) h 20-% toluene as diluent.

Table VI. Copolymerization of DBCA with An approximately equal maximum degradation isocyanates• rate temperature was observed for the homo­ polymer of DBCA and DBCA-chloral copoly­ Co monomer Conversion Isocyanateh mers (Table IV). This similarity was no surprise Concen- to polymer, content in because the degradation was determined by the Type tration, 96 product, % mol% stability of the end group and not by the slight changes in the side chain of the copolymer. PhNCO 50 91 38 Phenyl isocyanate could be very readily incorpo­ 20 46 27 rated by copolymerization into a DBCA poly­ 13 10 54 mer chain and the monomer content was almost 5 52 8 identical with the feed ratio of the monomers n-BuNCO 50 23 10 (Table VI). At higher phenyl isocyanate feed • Initiator, pyridine (2.5 mol%); polymerization concentrations the conversion to the polymer, bath temperature, - 78°C. however, decreased somewhat. Butyl isocyanate b Determined by elemental nitrogen analysis. was not as readily incorporated into the copoly­ mer and only a 10-% comonomer content in the chloral was more readily incorporated than the polymer was found at a feed ratio of 1 : I. DBCA in these copolymers regardless of the Figure 5 shows the infrared spectrum of a copoly­ polymerization temperature or the initiator used mer of DBCA and phenyl isocyanate. This (Figure 4). particular sample had 13-96 phenyl isocyanate

100 Cl 3 CCHO/Br2 CCICHO Copolymer (KBr)

Cl) u C "' .Et:: 40 .:::"' 20

o~..,,3~60""0;:-----:2""s.,,.o-=-o---=-20~0=-=o,---..,.1-=-60""0,----1""'2~0-.o---s-'-oo,--- Frequencv (cm- 1) Figure 4. IR spectrum (KBr pellet) of copolymer (about 1 : 2) of DBCA and chloral.

Polymer J., Vol. 9, No. 5, 1977 507 D. W. LIPP and 0. VoGL

100

80

Q) u 60 .E

"'C: i'.:"' 40 CICBroCHO/PhNCO Copolymer • (13%)

20

-0--""'3'"'5_.,o..,.o ____.....,.2.,.so~o,______2_0_0_0 _____1_6 ... 0_0 _____1..... 20_0 _____ 8_0 .... 0 __ _

Frequency (cm· 1 ) Figure 5. IR spectrum (KBr pellet) of copolymer of DBCA and PhNCO (13-% PhNCO content in polymer). in the copolymer and the IR spectrum shows and end group analysis for an acetyl carbonyl clearly the carbonyl band of the urethane linkage by IR spectroscopy. This constitutes a maxi­ in the polymer at 1740cm-1 • mum value because it is well-known that the The thermal degradation of phenyl isocyanate­ acetylation reaction is not quantitative, even DBCA copolymers in nitrogen is similar to that under vigorous conditions. The DP of the of the chloral-phenyl isocyanate copolymers. pyridine intiated polymer was estimated by in Two maximum rates of degradation occurred at situ chain termination with an acid chloride as 220°c and 250°C. previously described.13 By DSC poly-DBCA and DBCA copolymers The rate of polymerization of DBCA was showed no endotherms from -80°C to the determined by PMR spectroscopy by observing degradation points indicating that no glass transi­ the disappearance of the aldehyde monomer tion temperatures of the homopolymers or the proton peak by the method used for chloral copolymers with high concentration of DBCA in ref 14. The polymerization mixture when could be observed. taken below the threshold temperature formed Chloral-DBCA copolymers could also be a homogeneous gel in which the acetalic protons vacuum degraded in a sealed tube to the mono­ of the polymer were unobservable due to ex­ mers which were then analyzed by GC for the cessive line broadening, but the monomer proton copolymer composition. The data in Table V peak showed very little broadening as observed describing the composition of the copolymers in the system chloral-polychloral in ref 15. were obtained by vacuum degradation to the Hence the decrease of the aldehyde monomer monomers because the copolymers could not be peak integral served as a quantitative measure­ analyzed very well by elemental analysis owing ment of the rate of the polymerization. to the difficulties in the halogen analysis. In one particular case the rate study was Because of the insolubility of the polymers, carried out at -60°C. In general, it is desirable, molecular weights could not be determined in the case of perhaloacetaldehyde polymeri­ directly by solution techniques; it has been esti­ zations, to carry out a rate study at about 20°C mated that both pyridine and SbC1 5 initiated below the ceiling temperature of polymerization DBCA polymers have DP's in excess of 100. for consistency in thermodynamics. With pyri­ This estimate was obtained by treatment of the dine as the initiator at a 2-mol% level, it was

SbCl5 initiated polymer with acetic anhydride shown that the reaction levels off at 75% after

508 Polymer J., Vol. 9, No. 5, 1977 Haloaldehyde Polymers. X. about 1.5 hr; after 15 min, about 50% of the polymerization was completed. The rate of chloral polymerization is much faster at 20°C below the ceiling temperature. At 0°C, 50% of the polymerization is completed in less than 2 min. At - 78°C, in bulk, the polymerization is 30 Initiator Pyridine (3 mo1%) much faster and an ultimate conversion of 85% is reached after about 1 hr; a 50-% conversion .£ is achieved in about 10 min for DBCA (Figure 6). V) C The ceiling temperature of DBCA polymeri­ a, zation was estimated visually but a more accu­ ~20 E rate determination was carried out by an instru­ Cl) mental method; the polymer was insoluble in the monomer form and the point of the first appearance of opacity was detected passing a 10 light beam through the solution and measuring the intensity of transmitted light (Figure 7A). The threshold temperature was determined at monomer concentrations of 8.33 mol, 6.67 mol, 5.0 mol, and 2.5 mol in toluene. Extrapolation -10 -20 -30 -40 -of the data to a one-molar solution gave a ceil­ T (°C) ing temperature for a one-molar solution of Figure 7A. DBCA polymerization threshold tem­ -40°C (Figure 7B). perature determination: solvent, toluene; initiator, Polymerization of DBCA gave homopolymer pyridine (3 mol;?6); monomer concentration, 5 mo!. and copolymers similar to other perhaloacetal­ dehyde polymers. DBCA was much less reactive 0.9

RATE OF Br 2 CCICHO Polymerization 0.7

90

70 0.3 *C c• o § 50 Q) > 0.1 C 0 (.) 3.8 3.9 4.0 4.1 4.2 4.3 30 1/Tx103 Figure 7B. Graphic ceiling temperature determi­ nation of DBCA polymerization. 10 with cationic initiators than BDCA; it was also o,~-----'------'-2------J3'- less reactive under anionic conditions than BDCA Time(hr) or chloral. This lower reactivity reflected clearly Figure 6. NMR study of DBCA polymerization the lower ceiling temperature of DBCA poly­ rate: bath temperature, A, - 78°C; B, -60°C; merization. Also in copolymerizations, with initiator, pyridine (2 mol96); monomer concentra­ chloral, chloral is more readily incoporatied into tion, 8.3 M in toluene. the copolymers, especially at higher temperatures.

Polymer J., Vol. 9, No. 5, 1977 509 D. W. LIPP and 0. VoGL

Acknowledgments. Part of this work was sup­ Japan, Tokyo, 1974, No. 178. ported by the National Science Foundation. 6. B. Yamada, R. W. Campbell, and 0. Vogl, J. This paper was written when one of us Polym. Sci., Polym. Chem. Ed., 15, 1123 (1977). (O.V.) was on sabbatical leave at C.N.R.S. 7. B. Yamada, R. W. Campbell, and 0. Vogl, Polym. J., 9, 23 (1977). Centre de Recherches sur les Macromolecules, 8. R. W. Campbell, Thesis, University of Massa­ Strasbourg, France. We are indebted to L. S. chusetts, 1978. Corley for his efforts in the preparation of this 9. D. W. Lipp, Thesis, University of Massachu­ manuscript. setts, 1976. 10. D. W. Lipp and 0. Vogl, J. Polym. Sci., Polym. REFERENCES Chem. Ed., in press. 11. P. Kubisa and 0. Vogl, Macromol. Synth., 6, 1. 0. Vogl, H. C. Miller, and W. H. Sharkey, 49 (1977). Macromolecules, 5, 658 (1972). 12. A. L. Barney, U.S. Patent 3 067 173 (1962), 2. 0. Vogl, U.S. Patent 3 454 527 (1969). Chem. Abstr., 59, 103106 (1963). 3. 0. Vogl, U.S. Patent 3 699 184 (1972). 13. P. Kubisa and 0. Vogl, Polym. J., 7, 186 (1975). 4. I. Rosen and 0. Vogl, "Polyaldehydes," Marcel 14. K. Hatada, L. S. Corley, Sh. S. Vezirov, and Dekker, New York, N.Y., 1967, p 72. 0. Vogl, Vysokomol. Soedin., Ser. A, in press. 5. B. Yamada and 0. Vogl, Abstracts 25th Annual 15. 0. Vogl and K. Hatada, J. Polym. Sci., Polym. Meeting of the Society of Polymer Science, Lett. Ed., 13, 603 (1975).

510 Polymer J., Vol. 9, No. 5, 1977