Cationic polymerization of bis(1-alkylvinyl)benzenes and related monomers, 2. Controlled syntheses of 1,1,3-trimethyl substituted polyindanes

1,1,3-Trimethyl substituted polyindanes were synthesized in the presence of Brønsted acids (H₂SO₄, CF₃COOH) or Lewis acids (BCl₃, AlCl₃) using 1,4-diisopropenylbenzene ( 1 ), 1,4-bis(1-hydroxy-1-methylethyl)benzene ( 2 ) or 1,4-bis(1-chloro-1-methylethyl)benzene ( 3 ) as monomers. The effects of experimental conditions on yields, molar masses and polymer structure were studied in detail with respect to monomer and initiator used, their concentrations, reaction time and experimental procedure. It was shown, that polymerization temperatures above the ceiling temperature and low monomer concentrations favour the formation of indane units. However, in particular the uniformity of the polymer structure is sensitive to the experimental conditions, mainly to the initiator and to the procedure used. DSC measurements on the polymers proved the remarkable heat-resistance of polyindanes (T_dec. ≥ 450°C; T_g ≈ 210°C). The thermal properties were related to the polymer structure and were compared with those of some commercial polymers.