Gels of syndiotacticity-rich poly(vinyl alcohol)–water/dimethyl sulfoxide or – water/ethylene glycol solutions

Abstract

SynopsisGels of syndiotacticity-rich poly(viny1 alcohol) (s-PVA) in mixed solvents of water/dimethyl sulfoxide (DMSO) or water/ethylene glycol (EG) were made by chilling at the temperatures of 0-70 O C from those solutions with the polymer concentrations below 10 g/dL. The melting points of the gels were measured warming the gel from the gelling temperature (Tge,) at a constant heating rate. The apparent enthalpy of fusion of a junction of gel, AH was estimated from the relation between the apparent melting temperature and the polymer concentration. The s-PVA gels made from the mixtures of the water/lower contents of DMSO or EG had a minimum at lower Tgel and a maximum AH at a higher Tgel. On the other hand, the s-PVA gels made from the mixtures of the water/higher contents of them had nearly a maximum AH at a higher Tge,. From those results, it was considered that the former gels received a high thermal history while the latter gels received only slight thermal history.

Development and characterisation of an agar–polyvinyl alcohol blend hydrogel

“…These double helices are stabilised by the presence of water molecules bound inside the double helical cavity (Labropoulos et al, 2002a,b). PVOH can produce thermoreversible gels in many solutions such as water (Komatsu et al, 1986), ethylene glycol (Cebe and Grubb, 1985), dimethyl sulfoxide (DMSO) (Tanigami et al, 1994), Nmethylpyrrolidone (Hong and Miyasaka, 1991) and mixtures of these solvents (Hong et al, 2000;Yamaura et al, 1987). Furthermore, if a homogeneous high-temperature mixture of two components is rapidly cooled to a lower temperature, a sudden phase separation can set in.…”

Shape Memory Materials for Biomedical Applications

“…Without crosslinks, the use of the PVA gel is unfortunately limited in terms of thermal stability, [85] as heating this gel can in fact disrupt the hydrogen bonds and consequently the stability of the gel; this stability is also lost when the gel is placed in boiling water. [86] During the past 15 years, Nippon Zeon Co. and others [87±91] have developed a wide variety of SMPs. In the early 1997s, Liang et al [92] developed new, easy-to-shape polymers.…”

Rheological properties of syndiotacticity‐rich ultrahigh molecular weight poly(vinyl alcohol) dilute solution

“…6 -11 An aqueous solution of s-PVA formed hard elastic gel more easily than did that of a-PVA and the melting point of the s-PVA gel was remarkably higher than that of a-PVA gel. [12][13][14][15][16] a-PVA hydrogels for the drug delivery system have already been reported. [17][18][19][20][21][22][23] The gelation of PVA solution was suggested to occur with or without spinodal liquid-liquid phase separation according to the concentration and temperature of the solution.…”