Synthesis of β-Myrcene-Based Polymers and Styrene Block and Statistical Copolymers by SG1 Nitroxide-Mediated Controlled Radical Polymerization

Nitroxide-mediated polymerization (NMP) of beta-myrcene (My) at 120 degrees C in bulk using unimolecular SG1-based succinimidyl ester-functionalized BlocBuilder (BB) alkoxyamine resulted in low dispersity (D = 1.1-1.4) poly(myrcene)s P(My)s with high SG1 chain-end fidelity. The polymerizations also showed the number-average molecular weights (M-n) increased almost linearly with conversion. SG1-terminated P(My) macroinitiators were cleanly chain-extended with styrene (S) and the S-rich P(My-b-S) diblock copolymers exhibited two distinct glass transition temperatures (T(g)s), indicative of microphase separation. P(My-b-S) diblocks showed brittle stress strain behavior, plausibly due to relatively low M-n. My/S mixtures with initial S molar feed compositions f(s,0), = 0.10-0.94 were also statistically copolymerized (Mn = 8.2-19.8 kg mol(-1), D <= 1.37, and monomodal distributions). Copolymer reactivity ratios were rs = 0.25 +/- 0.04/0.34 +/- 0.19 and r(My), = 1.88 +/- 0.12/2.19 +/- 0.07 using Fineman-Ross and Kelen-Tudos methods. The statistical P(My-stat-S) copolymers displayed a range of T(g)s (-77 to +30 degrees C) depending on My molar fraction. My-rich and S-rich P(My-stat-S)s were then successfully chain-extended with both S and My.