Polymer
Polymer
4 years ago

Enhanced glass transition temperature of low molecular weight poly(methyl methacrylate) by initiator fragments located at chain ends

Enhanced glass transition temperature of low molecular weight poly(methyl methacrylate) by initiator fragments located at chain ends
We discovered important effects of chemically distinct initiator fragments incorporated at chain ends on the glass transition temperature (T g) of poly(methyl methacrylate) (PMMA). Polymers of various molecular weight (MW) were synthesized via free radical polymerization (FRP) using 2,2’-azobis(2-methylpropionitrile) (AIBN) and benzoyl peroxide (BPO) as initiator. All samples have identical triad distribution with ∼58% syndiotactic content. The T g values of ∼3 kg/mol PMMA possessing AIBN and BPO initiator fragments are 11–13 K higher than that of an anionic PMMA standard of similar MW. The elevated T g values in low MW PMMA synthesized by FRP are attributed to attractive interactions arising from polar chain ends. The T g-MW dependence becomes weaker at the lowest MWs examined in PMMA samples synthesized by FRP (with AIBN or BPO as initiator) and by anionic polymerization. The methodology of incorporating polar chain ends to increase the T g of low MW polymers provides new avenues for material design.

Publisher URL: www.sciencedirect.com/science

DOI: S0032386117306249

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