Branched aliphatic polycarbonates synthesis and coating applications

Abstract: The overall aim of this thesis is to describe the synthesisof branched aliphatic polycarbonates and show the potentialapplication of these polymers in the field of powder coatings.The characterization of the polycarbonates was facilitated bythe study of a series of bis-MPAdendrimers, which served asreference of perfectly branched polymers. In addition an?-caprolactone monomer with a bis-MPA pendant unit wassynthesized and polymerized in order to find an alternativesynthetic route hyperbranched polyesters.Cationic ring opening polymerization (CROP) of neopentylenecarbonate was utilized to synthesize a number of branchedpolymers. This monomer was chosen because the thermalproperties of poly(neopentylene carbonate) are promising forpowder coating applications. CROP enabled the synthesis ofbranched polymers, which are of great interest because of theirreduced melt viscosity and high functionality compared tolinear polymers. CROP of neopentylene carbonate, with a seriesof polyols including a hyper-branched polyester (Boltorn H30),in the presence of fumaric acid resulted in polymers withvaried degrees of branching and molecular weights ranging from2 000-100 000 g mol-1.Neopentylene carbonate was also used in the synthesispolycarbonate macromonomers possessing a polymerizablemethacrylate functional group at one of the chain ends. Inthjis case hydroxyethylmethacrylate was used as initiatopr inthe reaction catalyzed by methyl sulfonic acid. The MW of thismacromonomer was 2500 g mol-1and it was used to produce polymer brushes byfree radical and atom transfer radical polymerization(ATRP).An ?-caprolactone bearing a pendant bis-MPA wassynthesized and polymerized by Sn(Oct)2. Copolymerization with ?-caprolactone wasperformed to introduce linear segm,ents between the branchingpoints. The molecular weights of the homopolymer and thecopolymer were 3000 and 8000 g mol-1respectively as determined by Size exclusionchromatography (SEC) calibrated with polystyrene.SEC was used to analyze a series of bis-MPA dendrimers, andthe results were used to characterize the branchedpolycarbonates. The Mark-Houwink plots of the dendrimers wereproduced and used as reference in the characterization of thepolycarbonates.The thermal and rheological characterization of thepolycarbonates showed that the polymers were semi-crystallinewith Tgbetween 20-30 °C and Tmbetween 90-120 °C. Rheology measurementsshowed that the architecture had a considerable impact on themelt viscosity.Coating films were produced by UV curing of a series oflinear polycarbonates were functionalized with methacrylicgroups. The storage stability was tested for one week at 45°C, no coagulation of the particles was observed at theend of the testing period. The cured films showed good chemicalresistance and flexibility.