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 similar to 58% syndiotactic content. The Tg values of similar to 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. (C) 2017 Elsevier Ltd. All rights reserved.