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

Abstract

Nitroxide-mediated polymerization (NMP) of β-myrcene (My) at 120 °C in bulk using unimolecular SG1-based succinimidyl ester-functionalized BlocBuilder (BB) alkoxyamine resulted in low dispersity (Đ = 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 (Mn) 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 (Tgs), indicative of microphase separation. P(My-b-S) diblocks showed brittle stress–strain behavior, plausibly due to relatively low Mn. My/S mixtures with initial S molar feed compositions fS,0 = 0.10–0.94 were also statistically copolymerized (Mn = 8.2–19.8 kg mol–1, Đ ≤ 1.37, and monomodal distributions). Copolymer reactivity ratios were rS = 0.25 ± 0.04/0.34 ± 0.19 and rMy = 1.88 ± 0.12/2.19 ± 0.07 using Fineman–Ross and Kelen–Tudos methods. The stat...