Anionic Poly(ε-caprolactam):  Relationships among Conditions of Synthesis, Chain Regularity, Reticular Order, and Polymorphism

Abstract

Anionic poly ( -caprolactam), isothermally synthesized at temperatures between 155 and 195 °C by very fast carbamoyl-type activators, has been characterized by UV, DSC, and wide-angle X-ray scattering (WAXS) techniques in terms of high polymer yield, irregular structures along the chain, extent of cross-linking, Tg and Tm values, degree of crystallinity, and polymorphism. The specific role of four different activators on the above properties has been compared. From the whole set of characterization data it is evident that cyclohexylcarbamoylcaprolactam behaves as the most suitable activator and provides poly( -caprolactam) with properties that favorably match those of the corresponding hydrolytic polyamide.

Caprolactam-Laurolactam Copolymers: Fast Activated Anionic Synthesis, Thermal Properties and Structural Investigations

“…Our earlier work [6] gave a strong support in favor of the specific influence exerted by the activator chemical structure on polymer characteristics and properties. In the present paper hexamethylene dicarbamoylcaprolactam (HDCL) has been used as the activator.…”

“…[6] As is well known, properties and main characteristics of random copolymers are in first approximation linked to their overall composition. On this basis, we have studied in detail the changes of copolyamide behavior both in the case of high caprolactam (CL)/laurolactam (LL) molar ratios and when increasing LL content was used.…”

Polyamide from lactams by reactive rotational molding via anionic ring-opening polymerization: Optimization of processing parameters

“…As a result, crystallites formed during polymerization which led to much higher melting temperatures. When increasing the polymerization temperature from 160 to 180°C, a drop in the polymer melting [25]. Second, the increasing number of crystal imperfections induced by the formation of branch-points can cause a decrease in melting temperatures, simply because less energy is required in order to break down a crystal [26].…”

“…Second, the increasing number of crystal imperfections induced by the formation of branch-points can cause a decrease in melting temperatures, simply because less energy is required in order to break down a crystal [26]. It is reported for APA6 that branching can even cause a transition in the crystal structure [25], which is the third reason for the lower melting points. This is explained as follows.…”

“…Two types of crystals appear in anionic PA6, i.e., those with the $-structure (T m = 220°C) and those with the %-structure (T m = 214°C). For anionic PA6, it is reported that due to excessive branching, the % content can increase [25], hence reducing the melting point.…”