Reactions and structural changes during thermal annealing in a semicrystalline, aromatic diacetylene‐containing polyester

Abstract

Thermally induced solid‐state reactions and microstructure changes in a high molar mass, semicrystalline, aromatic diacetylene‐containing polyester, poly[2,4‐hexadiyn‐1,6‐ylene terephthalate], were investigated with a combination of laser Raman spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction analysis. The study has provided some new insights into the rather complex solid‐state reactions in the semicrystalline diacetylene‐containing polyester. Results suggest that, in addition to the usual desired solid‐state topochemical crosspolymerization in the crystalline region, a certain degree of random crosslinking reaction occurs in the amorphous region, especially when the annealing is carried out above the glass transition. After prolonged annealing or annealing at a higher temperature, a further reaction involving the formed polydiacetylene chains may occur, as evident from the reduction in crystallinity and even complete loss of crystallinity. An attempt has been made to separate the contribution of the topochemical reaction from the overlapping exothermic activities in the differential scanning calorimetry curves via subtraction. This allows the monitoring of the crystalline‐phase solid‐state topochemical crosspolymerization. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2354–2363, 2002

Non-topochemical Cross-linking of Amorphous Aliphatic Diacetylene-Containing Polymers

“…The cross-linking mechanisms of DA-containing polymers of Schemes 2 and 3, have so far been considered to be similar to that of the solid state cross-polymerization (Scheme 1), although Beckham and co-workers have mentioned that the amorphous regions also takes part in cross-linking through reactions other than PDA chain formation [6]. Hu and Li have reported the cross-linking of poly(2,4-hexadiyn-1,6-ylene terephthalate) and they mentioned the cross-linking takes place in the amorphous region at temperature below its T g [7]. Yu et al [8] have also studied the thermal crosslinking of poly(hexa-2,4-diynylen-1,6-dioxydibenzoate) containing an azobenzene group, and suggested that 1,2-and 1,4-additions, as well as cyclization took place.…”

Effect of metal salts in the optical properties of polydiacetylenes

“…PHDAz and PCDAz crystallinities were 28.4% and 26.2%, respectively. It is considered that the conversion to the corresponding PDAs depends on this percentage [31]. The diacetylene-containing polyesters were soluble in dichloromethane, THF and DMF.…”

Thermal properties of diacetylene–containing polymer prepared from propargyl-terminated monomer with pyridine

“…[35][36][37][38][39][40] In recent years, several correlative research studies have been reported on the synthesis and characteristics of diacetylene-containing polymers, for example, thermal properties and mechanical strength. [38][39][40][41] Many of the cured products were characterized by good mechanical and thermal properties and chemical resistance. Additionally, the unsaturated diacetylene groups in polymer backbone also conceive many other novel properties such as optical [42][43][44] and thermochromic properties.…”

“…[33][34][35][36] These obtained polymers can similarly undergo cross-linked polymerization under ultraviolet irradiation or by annealing at a definite temperature, and they exhibit enhanced mechanical properties and thermostability because of the volume contraction in the covalent coupling of adjacent diacetylene units. [35][36][37][38][39][40] In recent years, several correlative research studies have been reported on the synthesis and characteristics of diacetylene-containing polymers, for example, thermal properties and mechanical strength. [38][39][40][41] Many of the cured products were characterized by good mechanical and thermal properties and chemical resistance.…”