{'fraction_non_alphanumeric': 0.05583756345177665, 'fraction_numerical': 0.013959390862944163, 'mean_word_length': 4.7765567765567765, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Synthesis of Poly(α-methylstyrene-b-isobutylene) Copolymers by Living Cationic Sequential Block Copolymerization: Investigation on the Crossover from Living Poly(α-methylstyrene) Chain End to Isobutylene

The synthesis of poly(α-methylstryene-b-isobutylene) (P(αMeSt-b-IB)) copolymers via sequential monomer addition was studied using the adduct of the olefinic αMeSt dimer and HCl (DiαMeSt-HCl) as initiator in the presence of 2,6-di-tert-butylpyridine (DTBP) in methylcyclohexane (MeChx)/methyl chloride (MeCl) (60/40 v/v) at -80 °C. With BCl 3 employed as co-initiator in the first step of the synthesis, well-defined PαMeSt with controlled molecular weight and narrow molecular weight distribution (M w /M n = 1.05 ∼ 1.20) was obtained. Chain end decomposition was not detected for up to 30 min under monomer-starved condition. Model reactions using DiαMeSt.HCl indicated that, upon addition of IB, quantitative crossover takes place followed by immediate termination and the selective formation of PαMeSt-IB 1 -Cl. Therefore, the addition of TiCl 4 was necessary to polymerize IB. The obtained P(αMeSt-b-IB) diblock copolymer was found to be contaminated by a small amount of homo P(αMeSt), apparently formed via intramolecular alkylation. It has been shown that the blocking efficiency (B eff ) was a linear function of [IB], but this appeared to be very different for DiαMeSt-IB 1 -Cl and PαMeSt-IB 1 -Cl. This difference was attributed to selective solvation of PαMeSt-IB 1 -Cl by the solvent, which results in local [IB], which is about one-tenth of that in the bulk.