Preparation and Characterization of Cationic Poly Vinyl Alcohol with A

European Polymer Journal 47 (2011) 997–1004

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European Polymer Journal

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Preparation and characterization of cationic poly vinyl alcohol with a low degree of substitution ⇑ Pedram Fatehi a, , Robin Singh a,b, Zainab Ziaee a, Huining Xiao a, Yonghao Ni a a Department of Chemical Engineering, Limerick Pulp and Paper Centre, University of New Brunswick, Fredericton, NB, Canada E3B 5A3 b Department of Chemical Engineering, Indian Institute of Technology, Kharagpur, India article info abstract

Article history: The cationization of polymers has been regarded as an effective method to improve their Received 23 December 2010 performance for various applications. In this work, the cationization of poly vinyl alcohol Received in revised form 16 February 2011 (PVA) was investigated under different conditions, i.e., various glycidyl-trimethylammoni- Accepted 27 February 2011 um chloride (GTMAC) to PVA ratios, reaction temperatures, times, PVA and NaOH concen- Available online 3 March 2011 trations and solvent compositions. The results showed that the overall efficiency of the cationic modification was rather low, which was due to the hydrolysis of both GTMAC Keywords: and cationic-modified PVA (CPVA) under the strong alkaline conditions employed. The Cationization results also showed that the optimum GTMAC/PVA ratio depended on the solvent compo- Poly vinyl alcohol 1 AFM sition. The cationization was confirmed by means of H NMR and FTIR analyses. The max- NMR imum efficiency in water was obtained under the conditions of 95 °C, 1 h, 0.5 (mol) FTIR GTMAC/PVA ratio, and 5% (mol) NaOH concentration, while that in the ethanol/DMSO mix- Polymer ture (1.25 v/v) was obtained under the conditions of 70 °C, 1 h, 0.5 (mol) GTMAC/PVA ratio, and 5% (mol) NaOH concentration. Additionally, the interaction of CPVAs with a silicon wafer (as a substrate) was determined by employing an atomic force microscope (AFM) in water and air. Ó 2011 Elsevier Ltd. All rights reserved.

1. Introduction cationic PVA (CPVA) [5]. The highest MW of the resulting CPVA was 80,000–90,000. On the other hand, the cation- Cationic polymers have been applied in various indus- ization of already produced polymers on the basis of graft- tries for different purposes. For example, they have been ing is a simpler process since the cationization degree can used as strength agents or retention aids in papermaking be controlled without any effect on the molecular weight [1–4]. Copolymerization and grafting have been regarded of polymers. The modification of poly vinyl alcohol (PVA) as useful methods to induce tailored cationic polymers in using various chemical agents was reported in the litera- the literature [1,5]. ture [6–9]. Although copolymerization is an efficient method to In our previous work, the cationic-modified poly vinyl produce the cationic polymers, simultaneously controlling alcohol (CPVA) showed promising results in improving the molecular weight (MW) and charge density of the the pulp and paper strength [10,12–14], and the best re- resulting cationic polymers may be a challenging task, as sults were obtained at employing PVA with the molecular these properties are interrelated [5]. The copolymerization weight of 142,000–186,000 [11]. Additionally, it was found of vinyl acetate and diallyldimethyl ammonium chloride that the optimum charge density of CPVA for various fiber (DADMAC) was conducted in our previous work to produce systems may be different, varying between 0.3 and 0.72 meq/g, depending on the types of the fiber systems [10,12,13]. Therefore, it is important to understand the ⇑ Corresponding author. Tel.: +1 506 452 6084; fax: +1 506 453 4767. influence of parameters affecting the cationization of PVA E-mail address: [email protected] (P. Fatehi). with a tailored charge density.

In the literature, the cationization of starch and hemi- 2.3. CPVA characterization celluloses were conducted under various conditions, including wet or semi-dried environments [15–18]. The To determine the charge density of CPVAs, their solu- cationization reaction was also conducted in various sol- tions (1% wt.) were titrated against a PVSK standard solu- vents, e.g., water, ethanol or dimethyl sulfoxide (DMSO) tion (0.5 mM) by using a Particle Charge Detector Mütek [19,20]. In the cationization reaction, glycidyl-trimethy- PCD 03 (Herrsching, Germany). To quantify the degree of lammonium chloride (GTMAC) has been commonly used substitution of GTMAC with hydroxyl group on cationic- as a cationic reagent [15–20]. modified PVA (CPVA), CPVAs were dried at 105 °C over- 1 An atomic force microscopy (AFM) has been employed night, and their H NMR spectrum was recorded in D2O as a powerful device to investigate the interactions be- at 25 °C using an Oxford 300 MHz spectrometer operating tween various materials [21–23]. This device can be used at 300.13 MHz [8,9]. to determine how the charge of polymers influences The unmodified PVA and CPVA with the charge density their attraction/repulsion force with soft or hard surfaces. of 1.08 meq/g, which was prepared under the conditions of In this research, we aimed at understanding the factors 11% (wt.) PVA, 0.5 (mol) GTMAC/PVA ratio, 5% (mol) NaOH influencing the cationization of high MW PVA to induce concentration(based on PVA), 90 °C, 1 h, were character- CPVA with a low charge density (<1 meq/g) under vari- ized by using a Fourier transform infrared spectroscopy ous conditions. The parameters evaluated were: (FTIR) (Perkin Elmer Spectrum 100 FT-IR Spectrometer, GTMAC/PVA ratio, temperature, time, PVA concentration, USA). The oven-dried PVA or CPVA were embedded in solvent composition and NaOH concentration. The cati- KBr pellets in a mixture of about 1% (wt.) KBr. The spectra onization of PVA was confirmed qualitatively via FTIR were recorded in a transmittance mode in the range 800– and quantitatively via 1H NMR analyses. Based on these 3800 cmÀ1. results, the conditions that could induce the CPVA with a desired charge density and the maximum cationization 2.4. AFM analysis efficiency were determined. Moreover, the interaction of CPVA (having a low charge density of 0.2 meq/g or a In the literature, the AFM technique was employed to high charge density of 1.3 meq/g) with a silicon wafer determine the interaction between CPVAs and a hard sur- (as a substrate) was determined via employing an AFM face [21–23]. In fact, the silicon wafer with a 100 nm ther- in either water and air. mally oxidized layer was used as a model substrate for cellulose fibers [21–23]. In this work, similar silicon wafers

were first immersed in 98% H2SO4 for 6–8 h and rinsed 2. Experimental with deionised and distilled water prior to the use [21– 23]. To investigate the interaction of CPVA with the silicon 2.1. Raw materials wafers, an atomic force microscope (AFM) Nanoscope IIIa, Veeco Instruments Inc., Santa Barbara, CA, was employed. Poly vinyl alcohol (PVA) with a molecular weight (MW) The force analysis was conducted by using silica nitrate of 142,000–186,000 (99% hydrolyzed), glycidyl-trimethy- probes (NP-S20) with a spring constant of 0.32 N/m, and lammonium chloride (GTMAC, 75% in water), potassium a resonance frequency of 273 kHz. This silica probes were bromide (KBr, analytical grade), and dimethyl sulfoxide coated with CPVAs according to the following procedure: (99.7%, sterile-filtered), were all obtained from Sigma– at first, the probes were immersed in CPVA solutions (2% Aldrich, and used as received. Anionic polyvinyl sulfate wt.) overnight; then, the CPVA-coated probes were washed (PVSK) with a MW of 100,000–200,000 (97.7% esterified) with deionised and distilled water to remove unadsorbed was provided by Wako Pure Chem. Ltd. Japan. Ethanol CPVAs from the probes. The adhesion/repulsion force (95%) was received from Fisher Scientific. developed between the CPVA-coated probes and silicon wafers was measured in Picoforce mode with a vendor- supplied fluid cell at the temperature of 25 °C and the pH 2.2. CPVA preparation of 7 in water or in air. Each of 50 different spots was scanned 5 times on an area of 1 Â 1 lm2 at a constant tip In this research, 1 g of PVA was mixed with GTMAC un- velocity of 0.5 lm/s. The force-distance curves were ob- der various conditions. The reaction parameters investi- tained from cantilever deflection and displacement of the gated were: GTMAC/PVA ratio (0.25–2 mol), PVA piezo. concentration (4–33% wt.), solvent type (water, ethanol, ethanol/water or DMSO/ethanol), reaction time (20 min– 240 min) and temperature (60 °C–95 °C) and NaOH con- 3. Results and discussion centration (1–15% mol based on PVA). All the reactions were conducted in a 250 ml 3-neck glass flask under a con- 3.1. Preparation of cationic PVA stant stirring. The cationization reaction was stopped via neutralizing the solution using HCl (1 M). Then, the solu- 3.1.1. Effect of PVA concentration tions were cooled to room temperature, and unreacted Fig. 1 shows the charge density of the CPVA as a func- GTMAC was separated by dialyses membranes having a tion of PVA concentration. As can be seen, by increasing molecular weight cutoff of 1000, while changing water the PVA concentration from 4% to 33% (wt.), the charge every 2 h for the first 6 h and then once a day for 2 days. density of resulting CPVA increased from 0.22 meq/g to P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004 999

DMSO was mixed with 2.5 ml of ethanol and the reaction was conducted at 65 °C for 1 h (GTMAC/PVA molar ratio of 0.5). The resulting CPVA had a charge density of 0.61 meq/g. Thus, compared with the ethanol and ethanol/water solutions, the ethanol/DMSO solution was more effective in producing CPVA with a high charge density. Others have found that the ethanol/DMSO system was more effective than the ethanol and ethanol/water systems when cationizing starch [19,20]. Therefore, the remaining experiments were conducted under the semi-dried condition in the ethanol/DMSO system (1.25 v/v).

3.1.2. Effect of GTMAC/PVA molar ratio Fig. 2 shows the cationic modification of PVA as a function of GMTAC/PVA molar ratio in water or DMSO/ethanol. Clearly, the highest charge densities of 0.78 meq/g and 1.2 meq/g were obtained at GTMAC/PVA molar ratio of Fig. 1. Effect of PVA concentration on the charge density of CPVA (1 h, 0.5 in water and 1 in DMSO/ethanol solutions, respectively. 80 °C, GTMAC/PVA molar ratio = 0.5, [NaOH] = 5% (mol)). In the cationic modification of starch, the GTMAC/PVA molar ratio of 3 was optimum, which was due to the fact that starch has three hydroxyl groups in its repeating unit, 1 meq/g. In the literature, by increasing the molar ratio of which can react with GTMAC [19]. water/GTMAC from 2.8 to 100 (increasing the water con- By increasing the molar ratio of GTMAC to PVA, more tent of the system), the cationization efficiency of starch GTMAC was available for the cationization reaction. How- was reduced from 80% to 27% [16]. Also, it was reported ever, its hydrolysis would also occur at the same time. that the cationization efficiency of hemicelluloses using These results showed that, by increasing the molar ratio GTMAC was generally low, which was attributed to the of GTMAC/PVA more than 0.5 in water or 1 in the etha- hydrolysis of both GTMAC and resulting cationic hemicel- nol/DMSO mixture, more hydrolysis of GTMAC took place luloses under strong alkaline conditions [17,24–27].It under the alkaline conditions studied, which reduced the was reported that the hydrolysis of GTMAC under an alka- efficiency of the cationization [17,24–26]. Furthermore, a line condition mainly resulted in forming N-(2,3-dihy- higher charge density was obtained in the ethanol/DMSO droxy)propyl-N,N,N-trimethylammonium chloride, and mixture at 70 °C than in water at 80 °C, under otherwise dimer and trimer of GTMAC [15]. We propose that similar the same conditions. hydrolyses probably occurred in the GTMAC/PVA reaction system, which impaired the cationization efficiency of 3.1.3. Effect of reaction temperature PVA. The results in Fig. 1 imply that, at a low PVA concen- Fig. 3 shows the charge density of the cationic-modified tration, the hydrolysis of GTMAC can be more pronounced, PVA as a function of the reaction temperature in water or which is undesirable and reduces the efficiency of the cati- in the DMSO/ethanol solution. Interestingly, by increasing onization reaction. the reaction temperature from 60 °Cto95°C, the charge To improve the cationization efficiency, the reaction of density of resulting CPVA was significantly increased in PVA with GTMAC was conducted under semi-dried condi- water, which implied that a higher temperature favored tions. This method has been utilized for the cationization the cationization of PVA. However, a maximum charge of hemicelluloses in the past [17]. In one set of experi- density of 1.2 meq/g was achieved at 70 °C for the cation- ments, 1 g PVA granule (rather than PVA solutions) was ization in the ethanol/DMSO solution. Further increasing mixed with GTMAC with 2.5 ml of ethanol or with etha- the temperature resulted in a decrease in the charge den- nol/water mixture (2.5 v/v) at 65 °C for 1 h (GTMAC/PVA sity of CPVA in the ethanol/DMSO mixture. This behavior molar ratio of 0.5). The charge density of the resulting is probably due to the evaporation of ethanol from the eth- CPVAs were 0.23, 0.32 meq/g, respectively. As is well anol/DMSO solution. In the literature, the cationization known, the high MW PVA does not dissolve in pure ethanol efficiency of starch was lower in a pure DMSO solution under the conditions specified above. However, it can than that in the ethanol/DMSO solution [20]. dissolve in the ethanol/water mixture. Thus, the former system was heterogeneous, while the latter was homoge- 3.1.4. Effect of reaction time nous. It was reported that the efficiency of homogenous Fig. 4 shows the charge density of the CPVA as function cationization reaction of starch (in water) was higher than of the reaction time. Clearly, the maximum charge density the heterogeneous reaction (in ethanol) [20]. The higher of 0.80 meq/g was obtained at 1 h in water. By extending solubility of starch in water, which favored the cationic the reaction time, the charge density of CPVA in water reaction between starch and GTMAC, was the main reason was reduced. A similar trend was reported for the cation- for these results [20]. ization of hemicelluloses [17]. However, the maximum In another set of experiment, 1 g of PVA granule was charge density of 0.9 meq/g was obtained in the ethanol/ dissolved in 2 ml DMSO at 65 °C, and then cooled down DMSO solution after 1 h, and the further prolonging of to room temperature. Subsequently, the PVA solution in the reaction had a marginal effect on the cationization effi- 1000 P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004

Fig. 2. Effect of GTMAC/PVA molar ratio on the charge density CPVA, [NaOH] = 5% (mol), 1 h, (in water: [PVA] = 11%, 80 °C; in ethanol/DMSO (1.25 (v/v)), 70 °C).

Fig. 3. Effect of reaction temperature on the charge density CPVA at [NaOH] = 5% (mol) for 1 h. (in water: [PVA] = 11%, GTMAC/PVA molar ratio = 0.5; in ethanol/DMSO (1.25 v/v): GTMAC/PVA molar ratio = 1).

Fig. 4. Effect of reaction time on the charge density of CPVA, GTMAC/PVA molar ratio = 0.5, and [NaOH] = 5% (mol) (in water: [PVA] = 11%, 80 °C; in ethanol/ DMSO (1.25 v/v), 70 °C). P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004 1001 ciency. It was reported that, by prolonging the reaction each peak, which is 4.9% (mol) for the CPVA studied in time, the hydrolysis of cationic hemicelluloses was en- Fig. 6. The charge density of this CPVA can be theoretically hanced, which reduced the efficiency of the reaction calculated by considering the degree of substitution via the between GTMAC and hemicelluloses [17,23]. A similar 1H NMR analysis and assuming that each quaternary mol phenomenon probably happened here by prolonging the of ammonium groups attached to PVA backbone has a reaction time for GTMAC and PVA system in water. How- charge density of 1 eq. The charge density of the CPVA ever, the occurrence of side reactions was less in the via this 1H NMR analysis was 0.99 meq/g, which is in a ethanol/DMSO solution, as shown in Fig. 4. good agreement with that of 1.08 meq/g obtained via the PCD analysis. 3.1.5. Effect of NaOH The efficiency of the cationic modification can be deter- Fig. 5 shows the charge density of CPVA as a function of mined based on the degree of substitution analysis of 1H the NaOH concentration. As can be seen, the charge density NMR. In this respect, the efficiency is identified by consid- was the maximum via adding NaOH up to 5% (mol), ering the amount of GTMAC added to the system for the regardless of the solution media. A similar result was re- cationic reaction and the amount of GTMAC attached to ported by Wang and Xie on the cationization of corn starch the backbone of resulting CPVA. For the CPVA investigated [19]. Additionally, it was reported that NaOH functioned as in Fig. 6, the amount of GTMAC added was 0.5 mol (per a catalyst for the cationization of hemicelluloses and the mole of PVA) and the amount of GTMAC attached to PVA hydrolysis of GTMAC [15,19]. Thus, the concentration of backbone was 0.049 mol (per mol of PVA), which implied NaOH in solutions should be sufficient to promote the that the efficiency was about 10%. A similar analysis was main cationization reaction. However, excessive amount conducted on the other CPVAs produced, and the maxi- of NaOH would result in more extensive GTMAC and CPVA mum efficiency obtained in water was about 12% under hydrolyses. The results in Fig. 5 show that the maximum of the conditions of 95 °C, 1 h, GTMAC/PVA molar ratio of 5% (mol) was sufficient to obtain the maximum cationiza- 0.5 (mol), and the NaOH concentration of 5% (mol). The tion efficiency, regardless of the cationization medium. maximum efficiency in the ethanol/DMSO mixture was about 10% under the conditions of ethanol/DMSO (1.25 v/ 3.2. Characterization of CPVA v), 70 °C, 1 h, GTMAC/PVA molar ratio of 0.5, and NaOH concentration of 5% (mol). The rather low efficiency is The reaction scheme of GTMAC with PVA was reported due to the occurrence of the side reactions, as discussed in our previous work [10]. Fig. 6 shows the 1H NMR spec- earlier. The cationic modification of PVA or hemicelluloses trum of CPVA. The peak at 3.2 ppm belongs to protons at- using other cationic agents was also reported to be less tached to the quaternary ammonium group of the PVA than 10% [7,24,27]. The results in Figs. 2 and 3 also shows backbone, which confirmed the cationic modification of that the maximum charge density of CPVA was approxi-

PVA [7]. The peak at 4 ppm is assigned to the CH2 of the mately 1.2 meq/g, regardless of the solvent composition; PVA backbone, while the peaks between 3.2 and 3.8 ppm while the reaction efficiency was higher in ethanol/DMSO are due to the CH2 of the attached cationic group on the system than in water system at any GTMAC/PVA molar ra- PVA backbone. Also, the peaks between 1.5–2 ppm belong tio studied (Fig. 2). to CH of the PVA backbone. The degree of substitution can Fig. 7 shows the FTIR spectrum of unmodified PVA be quantified by considering the areas under the peaks at and the CPVA sample investigated in Fig. 6. A similar 3.2 and 4 ppm and the number of protons associated with spectrum was reported for unmodified PVA in the litera-

Fig. 5. Effect of NaOH concentration (mol) on the charge density of CPVA, 1 h (in water: [PVA] = 11%, GTMAC/PVA molar ratio = 0.5, 80 °C; in ethanol/DMSO (1.25 v/v): GTMAC/PVA molar ratio = 1 at 70 °C). 1002 P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004

Fig. 6. 1H NMR spectrum of cationic PVA (CPVA) prepared under the following conditions: [NaOH] = 5% (mol), [PVA] = 11%, 90 °C, 1 h, GTMAC/PVA molar ratio = 0.5.

Fig. 7. FTIR spectra of original PVA and cationic PVA (CPVA) prepared under the following conditions: [NaOH] = 5% (mol), [PVA] = 11%, 90 °C, 1 h, GTMAC/ PVA molar ratio = 0.5. ture [28,29]. The peak at 2850–3000 cmÀ1 is assigned to (C–O–C bond) provides the evidence of the ether linkages C–H broad alkyl stretching band, 3600–3650 cmÀ1 to – between GTMAC and PVA [24]. Additionally, an increase OH stretching band, and 3200–3570 cmÀ1 to hydrogen was observed on the intensity of the absorption at À1 bonding of the PVA molecule. The peak at 1090– 1462 cm , which could be assigned to CH2 bending 1150 cmÀ1 is assigned to C–O band [30]. An increase in and methyl groups of the GTMAC, which is now a part the intensity of the absorbance at 1044 cmÀ1 of CPVA of the resulting CPVA [24,31]. P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004 1003

3.3. Adhesion/repulsion force with a charge density of 1.3 meq/g was strong (À70 mN/ m), while the adhesion force for the CPVA having a charge Fig. 8 shows the adhesion force developed between the density of 0.2 meq/g was weak (À15 mN/m). From the re- CPVA-coated AFM-probe and the silicon wafer in water. sults of Figs. 8 and 9, it can be inferred that the interaction Interestingly, the adhesion force (À1.5 mN/m) developed between the CPVAs and oppositely charged surfaces (sili- for the CPVA having a charge density of 1.3 meq/g, was con wafers) is more signiﬁcant in air than that in water, higher than that (À0.2 mN/m) for the CPVA having a which may be due to the fact that the water molecules charge density of 0.2 meq/g. A similar adhesion force can screen some of the charges of CPVAs in aqueous solu- (À1 mN/m) has been reported between the AFM-probe, tions [34]. coated with cationic starch having a charge density of In the above AFM force analysis, the approaching phase 0.5 meq/g, and a silicon wafer [32,33]. In contrast, a mar- of the CPVA-coated AFM probe to the silicon wafer resem- ginal interaction between the uncoated AFM-probe and bles the approaching of CPVA segment to a hard/soft sur- the wafer was observed either in water or air. face for adsorption. Therefore, the attraction/repulsion Fig. 9 shows the adhesion/repulsion force developed be- force simulates the interaction of the CPVA with the sur- tween the AFM-probes, coated with the same CPVAs, and faces [12]. The results show that the CPVA with a high the silicon wafer in air. The adhesion force for the CPVA charge density (1.3 meq/g) has a higher afﬁnity for the

Fig. 8. Adhesion/repulsion force developed between the AFM-probes, coated with CPVAs having different charge densities (meq/g), and silicon wafer in retrace mode in water.

Fig. 9. Adhesion/repulsion force developed between the AFM-probes, coated with CPVAs having different charge densities (meq/g), and silicon wafer in retrace mode in air. 1004 P. Fatehi et al. / European Polymer Journal 47 (2011) 997–1004 adsorption compared with the CPVA with a low charge [11] Fatehi P, Xiao H. Effect of cationic PVA characteristics on fiber and density (0.2 meq/g). paper properties at saturation level of polymer adsorption. Carbohyd polym 2010;79:423–8. [12] Fatehi P, Liu X, Ni Y, Xiao H. Interaction of cationic modified poly 4. Conclusions vinyl alcohol with high yield pulp. Cellulose 2010;17:1021–31. [13] Fatehi P, McArthur T, Xiao H, Ni Y. Improving the strength of old corrugated carton pulp (OCC) using a dry strength additive. Appita In this work, the PVA cationization efficiency was deter- 2010;63(5):364–9. mined as functions of a number of process parameters. The [14] Fatehi P, Ward JE, Ates S, Ni Y, Xiao H. Impact of cationic poly (vinyl results showed that the overall efficiency of the cationiza- alcohol) on the properties of papers made from two different pulps. Appita 2009;62(4):303–7. tion was rather low, which was due to the hydrolysis of [15] Kavaliauskaite R, Klimaviciute R, Zemaitaitis A. Factors influencing GTMAC and CPVA under the strong alkaline environment. production of cationic starches. Carbohyd Polym 2008;73:665–75. The optimum GTMAC/PVA molar ratio was 0.5 in water [16] Bendoraitiene J, Kavaliauskiate R, Klimaviciute R, Zemaitaitis A. Peculiarities of starch cationization with glycidy-methylammonium and 1 in the ethanol/DMSO mixture (1.25 v/v). The maxi- chloride. Starch 2006;58:623–31. mum charge density was obtained after 1 h and a further [17] Z. Liu, Y. Ni, P. Fatehi, A. Saeed, Isolation and cationization of extension of the reaction time reduced the charge density hemicelluloses from pre-hydrolysis liquor of the kraft-based dissolving pulp production process, Biomass Bioen. 2010, of CPVA. The maximum efficiency in water was obtained doi:10.1016/j.biombioe.2011.01.008. under the conditions of 95 °C, 1 h, GTMAC/PVA molar ratio [18] Tuting W, Wegemann K, Mischnick P. Enzymatic degradation and of 0.5, and 5% (mol) NaOH concentration; while that in the electrospray tandem mass spectroscopy as tools for determining the structure of cationic starches prepared by wet and dry methods. ethanol/DMSO mixture was obtained under the conditions Carbohyd Res 2004;339:637–48. of 70 °C, 1 h, GTMAC/PVA molar ratio of 0.5, and 5% (mol) [19] Wang Y, Xie W. Synthesis of cationic starch with a high degree of NaOH concentration. Additionally, the attraction force substitution in an ionic liquid. Carbohyd Polym 2010;80:1172–7. [20] Heinze T, Haack V, Rensing S. Starch derivatives of high degree of developed between a silicon wafer and the AFM-probe functionalization. 7. Preparation of cationic 2-hydroxypropyltri- coated with CPVA having a charge density of 1.3 meq/g methylammonium chloride starches. Starch 2004;56:288–96. was larger than that developed between the silicon wafer [21] Paakko M, Vappavuori J, Silvennoinen R, Kosonen H, Ankerfors M, and the AFM-probe coated with CPVA having a charge den- Lindstrom T, et al. Long and entangled native cellulose i nanofibers allow flexible aerogels and hierarchically porous templates for sity of 0.2 meq/g. The attraction force was significantly functionalities. Soft Mat 2008;4:2492–9. higher in air than in water under otherwise the same [22] Ouajai S, Shanks RA. Solvent and enzyme induced recrystallization of conditions. mechanically degraded hemp cellulose. Cellulose 2006;13:31–44. [23] Wang J, Feldberg SW, Bard AJ. Measurement of double-layer forces at the polymer film/electrolyte interfaces using atomic force Acknowledgments microscopy: concentration and potential-dependent interactions. J Phys Chem B 2002;106:10440–6. [24] Ren JL, Peng F, Sun RC, Liu CF, Cao ZN, Luo W, et al. Synthesis of The financial support for this project is from an NSERC cationic hemicellulosic derivatives with a low degree of substitution Strategic Net Work (ForValueNet) and Atlantic Innovation in dimethyl sulfoxide media. J Appl Polym Sci 2008;109:2711–7. Fund (AIF). [25] Bendoraitiene J, Kavaliauskaite R, Kilmaviciute R, Zemaitaitis A. Peculiarities of starch cationization with glycidyl- trimethylammonium chloride. Starch 2006;58(12):623–31. References [26] Ren JL, Peng F, Sun RC, Kennedy JF. Influence of hemicellulosic derivatives on the sulfate kraft pulp strength. Carbohy Polym [1] Gaiolas C, Costa AP, Santos Silva M. Influence of cationic starch 2009;75:338–42. addition on printing grade paper formation. Cell Chem Technol [27] Xie W, Wang Y. Synthetic pf cationic starch with a high degree of 2006;40(9–10):783–90. substitution in an ionic liquid. Carbohyd Polym 2010;80:1172–7. [2] Gaiolas C, Mendes P, Silva M. The role of cationic starch in carbonate- [28] Hema M, Selvasekarapanadian S, Arunkumar D, Sakunthala A, filled papers. Appita 2005;58(4):282–7. Nithya H. FTIR, XRD and ac impedance spectroscopic study on PVA [3] Baba Y. New paper strength agent from grafted starch. Japan Tappi J based polymer electrolyte doped with NH4X (X = Cl, Br, I). J 2001;55(9):11–6. Noncrystal Sol 2009;355:84–90. [4] Xiao H, Pelton P, Hamielec A. Novel retention aids for mechanical [29] Jia X, Li Y, Cheng Q, Zhang S, Zhang B. Preparation and properties of pulps. Tappi J 1996;79(4):129–35. poly (vinyl alcohol)/silica nanocomposites derived from [5] Sang Y, Xiao H. Preparation and application of cationic cellulose copolymerization of vinyl silica nanocomparticles and vinyl fibers modified by in situ grafting of cationic PVA. Colloid Surf A: acetate. Euro Polym J 2007;43:1123–31. Physicochem Eng Aspects 2009;335(1–3):121–7. [30] Mansur HS, Orefice RL, Mansur AAP. Characterization of poly (vinyl [6] Moritani T, Yamauchi J. Functional modification of poly (vinyl alcohol)/poly (ethylene glycol) hydrogels and PVA-derived hybrids alcohol) by copolymerization: II. Modification with a sulfonate by small-angle X-ray scattering and FTIR spectroscopy. Polymer monomer. Polymer 1998;39(3):553–7. 2004;45:7193–202. [7] Moritani T, Yamauchi J. Functional modification of poly (vinyl [31] Kacurakova M, Ebringerova A, Hirsch J, Hromadkova Z. Infrared alcohol) by copolymerization: III. Modification with cationic study of arabinoxylans. J Sci Food Agri 1994;66:423–7. monomers. Polymer 1998;39(3):559–72. [32] Guan Y, Qian L, Xiao H, Zheng A, He B. Synthesis of a novel [8] Moritani T, Kajitani K. Functional modification of poly (vinyl alcohol) antimicrobial-modified starch and its adsorption on cellulose fibers: by copolymerization: I. Modification with carboxylic monomers. part II – Adsorption behaviors of cationic starch on cellulose fibers. Polymer 1997;38(12):2933–45. Cellulose 2008;15:619–29. [9] Moritani T, Okaya T. Functional modification of poly (vinyl alcohol) [33] Abraham T, Christendat D, Xu Z, Masliyah J, Gohy JF, Jerome R. Role by copolymerization: IV. Self-crosslinkable poly (vinyl alcohol)s. of polyelectrolyte charge density in tuning colloidal forces. AIChE J Polymer 1998;39(4):923–31. 2004;50(10):2613–26. [10] Fatehi P, Xiao H. Adsorption characteristics of cationic-modified poly [34] Leite FL, Riul AJR, Herrmann PSP J. Mapping of adhesion forces on (vinyl alcohol) on cellulose fibers – A qualitative analysis. Colloid soil minerals in air and water by atomic force spectroscopy (AFS). Surf A: Physicochem Eng Aspects 2008;327(1–3):127–33. Adhesion Sci Technol 2003;17(16):2141–56.