LCST-type phase behavior of poly(2-chloroethyl vinyl ether-alt-maleic anhydride) in n-butyl acetate

Abstract

Novel polymer solutions exhibiting lower critical solution temperatures (LCSTs) have been studied. An alternating copolymer of 2-chloroethyl vinyl ether and maleic anhydride was synthesized through free-radical solution polymerization. This copolymer can exhibit LCST-type phase behavior in n-butyl acetate (BuAc) under relatively mild conditions at temperatures sufficiently below its boiling point. The effects of molecular weight, polymer concentration and addition of cosolvent on the polymer solution's cloud point temperature (T cp ) were investigated. The T cp value was nearly constant over a wide range of concentrations and increased when the polymer concentration was reduced below a certain value. The experimental LCST-type phase diagram can be reasonably described by Flory-Huggins theory. The addition of non-solvents could reduce the T cp of the polymer solution in BuAc, whereas the addition of good solvents could increase the T cp . These LCST-type phase behaviors may be attributed to specific polar interactions between the polymer and the solvent. INTRODUCTIONLower critical solution temperature (LCST)-type phase behavior in polymer solutions has been attracting a great deal of attention over the past decade. Polymers that exhibit LCST are a class of stimuli-sensitive polymers that are soluble at temperatures below the LCST and become insoluble above the LCST. Many studies have focused on LCST-type phase behavior in aqueous polymer solutions, and many theories and applications have been developed. 1-3 Today, LCST-type phase behavior of polymers in nonaqueous media is also attracting interest as an opportunity for research and development of smart materials. For example, LCST polymer solutions of thermoresponsive polymer/ionic liquid systems have been reported. [4][5][6][7] Conventional LCST polymer solutions in organic media have critical temperatures that are higher than the boiling points (BPs) of the solvents. [8][9][10][11][12][13][14] These reported systems can exhibit LCST-type phase behavior under some extreme conditions, for example, in sealed highpressure cells above the BP of the solvent or using considerably highmolecular-weight polymers. Some theories have been proposed to explain or predict this type of LCST-type phase behavior. [15][16][17] In freevolume theories, the difference between the densities or the expansion coefficients of the polymer and the solvent above the solvent's BP is proposed to cause phase separation at elevated temperatures. 17 Because these conditions are inconvenient to study, a novel polymer/organic media solution that can present LCST under mild

A new thermo-responsive block copolymer with tunable upper critical solution temperature and lower critical solution temperature in the alcohol/water mixture

“…Different from the co‐solvent effect on LCST, the addition of the nonsolvent of octane in the poly(2‐chloroethyl vinyl ether‐alt‐maleic anhydride) solution in n ‐butyl acetate leads to the LCST decreasing, and the reason was due to the nonsolvent disturbing the solvation shell around the polymer chains, resulting in the decreased solubility of the polymer in the solvent . The similar nonsolvent effect on the solubility of PVEA is also observed.…”

“…For thermo‐responsive polymers, the LCST or UCST generally can be tuned by addition of co‐solvent or nonsolvent . For example, the LCST of PNIPAM in water decreases from 32.5 to −7.5 °C when 35 vol % methanol is added and then increases with the further addition of methanol .…”

Polymethacrylic Acid Shows Thermoresponsivity in an Organic Solvent

“…It is counteracted by the presence of water. Understanding the LCST mechanism in pMAA/DME solutions could enlighten the more complex scenario of LCST in alternating sequence-controlled copolymer solutions in organic solvents. − These homopolymer systems, pMAA and pHEA, are the elementary bricks of random and alternating sequence-controlled methacrylic acid/hydroxyethyl acrylate copolymers, noted, respectively, p­(MAA- co -HEA) and p­(MAA- alt -HEA), where the differences in sequence seem to play a key part. A distinctive feature of the random copolymer is the presence of homoblocks AA, AAA, AAAA, and so forth, which cannot exist in the alternating copolymer.…”

A New Family of Thermo-Responsive Polymers Based on Poly[N-(4-vinylbenzyl)-N,N-dialkylamine]

“…33,34 On the contrary, addition of the nonsolvent of octane in the poly(2chloroethyl vinyl ether-alt-maleic anhydride) solution in n-butyl acetate leads to the LCST decrease. 30 The UCST-type polymers undergo phase transition usually in a polar organic solvent, 11−17 although those such as polysulfobetaine, 39 poly-(N-acryloylasparaginamide) 40 and poly(N-acryloyl glycinamide) 41 in water are reported. The UCST is usually correlative to the polymer molecular weight, 14,16,40 and high polymer molecular weight generally leads to high UCST.…”