Eco-friendly synthesis of carbon fiber precursor polymers and their molecular characteristics

Abstract

Carbon fiber precursor polymers such as poly[acrylonitrile-co-itaconic acid], poly[acrylonitrile-co-acrylamide] copolymers were synthesized through green chemistry routes i.e., via solid phase polymerization without using solvents, employing aqueous soluble inorganic metal salts as template compounds. The composition and the average molecular weights, such as the number average molecular weight (M_n), viscosity average molecular weight (M_v), weight average molecular weight (M_w) and size average molecular weight (M_z), were determined. The molecular weight distributions were evaluated by the M_v : M_n ratios estimated from the viscosity and osmotic measurements, and the M_w/M_n values were estimated from size exclusion chromatography (SEC-LALLS). The molecular weight distributions of these polymers, as determined from M_v/M_n and M_w/M_n, were 2.1 to 3.2 and 2.1 to 2.5 respectively. The molecular parameters [M_n (4.7 × 10⁴), M_v (1.64 × 10⁵), M_w (1.17 × 10⁵) g mol⁻¹] are comparable to those obtained through suspension [M_n (4.25 × 10⁴), M_v (2.09 × 10⁵), M_w(1.82 × 10⁵) g mol⁻¹] and solution [M_n (4.28 × 10⁴), M_v (1.61 × 10⁵), M_w(1.43 × 10⁵) g mol⁻¹] polymerization processes (conventional). The dispersity of the polymer spinning solution was also investigated using a parallel plate viscometer which confirms the homogeneity of the solution.