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Peter Löwenhielm BRANCHED ALIPHATIC POLYCARBONATES: SYNTHESIS AND COATING APPICATIONS Peter Löwenhielm Akademisk avhandling Som med tillstånd av Kungliga Tekniska Högskolan i Stockholm framlägges till offentlig granskning fredagen den 24e september 2004, kl 10.00 i sal E2, Osquars backe 2, KTH, Stockholm. Avhandlingen försvararas på engelska ABSTRACT The overall aim of this thesis is to describe the synthesis of branched aliphatic polycarbonates and show the potential application of these polymers in the field of powder coatings. The characterization of the polycarbonates was facilitated by the study of a series of bis-MPA dendrimers, which served as reference of perfectly branched polymers. In addition an ε- caprolactone monomer with a bis-MPA pendant unit was synthesized and polymerized in order to find an alternative synthetic route hyperbranched polyesters. Cationic ring opening polymerization (CROP) of neopentylene carbonate was utilized to synthesize a number of branched polymers. This monomer was chosen because the thermal properties of poly(neopentylene carbonate) are promising for powder coating applications. CROP enabled the synthesis of branched polymers, which are of great interest because of their reduced melt viscosity and high functionality compared to linear polymers. CROP of neopentylene carbonate, with a series of polyols including a hyper-branched polyester (Boltorn H30), in the presence of fumaric acid resulted in polymers with varied degrees of branching and molecular weights ranging from 2 000-100 000 g mol-1. Neopentylene carbonate was also used in the synthesis polycarbonate macromonomers possessing a polymerizable methacrylate functional group at one of the chain ends. In thjis case hydroxyethylmethacrylate was used as initiatopr in the reaction catalyzed by methyl sulfonic acid. The MW of this macromonomer was 2500 g mol-1 and it was used to produce polymer brushes by free radical and atom transfer radical polymerization (ATRP). Αn ε-caprolactone bearing a pendant bis-MPA was synthesized and polymerized by Sn(Oct)2. Copolymerization with ε-caprolactone was performed to introduce linear segm,ents between the branching points. The molecular weights of the homopolymer and the copolymer were 3000 and 8000 g mol-1 respectively as determined by Size exclusion chromatography (SEC) calibrated with polystyrene. SEC was used to analyze a series of bis-MPA dendrimers, and the results were used to characterize the branched polycarbonates. The Mark-Houwink plots of the dendrimers were produced and used as reference in the characterization of the polycarbonates. The thermal and rheological characterization of the polycarbonates showed that the polymers were semi-crystalline with Tg between 20-30 °C and Tm between 90-120 °C. Rheology measurements showed that the architecture had a considerable impact on the melt viscosity. Coating films were produced by UV curing of a series of linear polycarbonates were functionalized with methacrylic groups. The storage stability was tested for one week at 45 °C, no coagulation of the particles was observed at the end of the testing period. The cured films showed good chemical resistance and flexibility. SAMMANFATTNING Detta arbete beskriver i huvudsak syntes av grenade alifatiska polykarbonater och en studie av dessa för tillämpning inom pulverfärger. Vidare har en serie dendrimer studerats och använts som referens i karakteriseringen av polykarbonaterna. Slutligen har en lakton monomer syntetiserats och ringöppnings polymerisation har använts som en alternativ syntesväg till hyperförgrenade polyestrar. Katjonisk ringöppningspolymerisation användes för att syntetisera ett antal polymerer av neopentylkarbonat. Denna monomer användes eftersom dess polymers termiska egenskaper är lovande för tillämpningar som pulverfärger. Användandet av ringöppningspolymerisation möjliggjorde syntes av stjärn polymerer vilka är intressanta eftersom de uppvisar en låg viskositet i förhållande till molekylvikt och dessutom har en hög funktionalitet. Polymerisationer av neopentylkarbonat tillsammans med en serie kommersiella polyoler, innefattande en hyperförgrenad polyester (Boltorn H30) skedde i närvaro av fumarsyra och resulterade i polymerer med varierande förgreningsgrad och molekylvikter från 2 000 till 100 000 g mol-1. Neopentylkarbonat användes också för att syntetisera makromonomerer där den ena kedje ändan bestod av en polymeriserbar akrylatgrupp. Reaktionen utfördes i lösning med hydroxyetylmetakrylat som initatiatior och metylsulfonsyra som katalysator. Makromonomen polymeriserades sedan med fri radikalpolymerisation och kontrollerad radikalpolymerisation för framställning av kampolymerer. En ε-caprolakton monomer modifierad med bis-metylol propionsyra syntetiserades och polymeriserades genom katalys av Sn(Oct)2. Sampolymerisation utfördes också tillsammans med ε-caprolakton för att introducera linjära segment mellan förgreningspunkterna. Molekyl vikten till 3000 g mol-1 för homopolymeren och 8000 g mol-1 för sampolymeren. Förgrenings graderna beräknades med 1H-NMR till 0,50 och 0,15 för homopolymeren respektive sampolymeren. Ett antal bis-MPA dendrimerer studerades med kromatografi och viskosimetri. Mark- Houwink plotter konstruerades och användes som referenser i studierna av de grenade polykarbonaterna. Analys av polykarbonaternas termiska och reologiska egenskaper visade att polymererna var kristallina uppvisande Tg = 20-30°C och Tm = 90-120°C. Reologi mätningarna visade att arkitekturen hade en betydande inverkan på smältviskositeten. Slutligen tillverkades filmer baserade på linjära polykarbonater med tre olika molekylvikter. Polymerernas kedjeändar hade funktionaliserats med akrylatgrupper för att möjliggöra tvärbindning med UV-härdning. Pulvrets lagrings stabilitet testades genom förvaring vid 45°C i en vecka. Efter testperioden konstaterades att partiklarna ej koagulerat vilket är ett techen på god lagringsstabilitet. De härdade filmerna uppvisade god kemikalie resistens och flexibilitet. LIST OF PAPERS The thesis is a summary of the following papers: I “Poly(neopentylene carbonate) Hyperstars”, P. Löwenhielm, H. Claesson, A. Hult, Macromolecular Chemistry and Physics, 2004, 205, 1489-1496 II “New Approach to Hyperbranched Polyesters: Self-condensing Cyclic Ester Polymerization of Bis(hydroxymethyl)-Substituted ε-Caprolactone” M.Trollsås, P. Löwenhielm, V.Y. Lee, M. Möller, R.D. Miller, and J.L. Hedrick, Macromolecules, 1999, 32, 9062-9066 III “Synthesis and Characterization of 2,2-Bis(methylol)propionic Acid Dendrimers with Different Cores and Terminal Groups” M. Malkoch, H.Claesson, P. Löwenhielm, E. Malmström, A. Hult, Journal of Polymer Science: Part A: Polymer Chemistry, 2004, 42, 1758-1767 IV “Aliphatic Polycarbonate Resins for Radiation Curable Powder Coatings” P. Löwenhielm, D Nyström, M. Johansson, A. Hult, Manuscript The thesis also contains results part of a manuscript in preparation: “Synthesis and characterization of poly(neopentylene carboanate) brushes” TTABLE OF CONTENTS 1 PURPOSE OF THE STUDY.................................................................................... 3 2 INTRODUCTION ..................................................................................................... 4 2.1 Powder Coatings................................................................................................................. 4 2.2 Polymer architecture.......................................................................................................... 8 2.2.1 Long chain branching.................................................................................................... 9 2.2.2 Dendritic polymers........................................................................................................9 2.3 Ring opening polymerization .......................................................................................... 10 2.3.1 Polyesters .................................................................................................................... 11 2.3.2 Polycarbonates ............................................................................................................ 11 3 EXPERIMENTAL .................................................................................................. 15 3.1 Materials ........................................................................................................................... 15 3.2 Synthesis............................................................................................................................ 15 3.2.1 Synthesis of neopentyl carbonate................................................................................ 15 3.2.2 Cationic ring opening polymerization of neopentylcarbonate with fumaric acid....... 15 3.2.3 Synthesis of acrylate terminated poly(neopentyl carbonate) macromonomer............ 16 3.2.4 Synthesis of poly(neopentyl carbonate) brushes......................................................... 16 3.2.5 Synthesis of hyperbranched polyesters by ring opening polymerization.................... 17 3.2.6 Characterization of Bis-MPA dendrimers................................................................... 18 3.2.7 Functionalization of polycarbonates for crosslinking ................................................. 18 3.2.8 Crosslinking of acrylate functional polycarbonates.................................................... 18 3.3 Characterization methods ............................................................................................... 19 3.3.1 NMR...........................................................................................................................
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