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 ( 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 ( M n = 8.2–19.8 kg mol –1, Đ ≤ 1.37, and monomodal distributions). Copolymer reactivity ratios were r S = 0.25 ± 0.04/0.34 ± 0.19 and r My = 1.88 ± 0.12/2.19 ± 0.07 using Fineman–Ross and Kelen–Tüdös methods. The statistical P( My - stat -S) copolymers displayed a range of T g s (−77 to +30 °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 .