Extraordinarily Large LCST Depression Converts Nonthermosensitive Polymer to Thermosensitive

Abstract

A facile method to tune the phase transition temperature of thermosensitive polymers is to introduce an additive; however, the influence of additives is usually limited. Here the influence of poly­(vinyl alcohol) (PVA), a polymeric additive, on thermal behavior of copolymers of acrylamide (AAm), N,N-dimethyl­acrylamide (DMAA), and 3-(acrylamido)­phenyl­boronic acid (3-AAPBA), P­(AAm-DMAA-3-AAPBA), was studied. With increasing AAm content, the phase transition temperature of the copolymers increases gradually. They finally become nonthermosensitive when AAm content exceeds 20 mol %. To study the influence of PVA on the copolymers, they were incorporated into thin films via layer-by-layer (LBL) assembly, using phenylboronate ester bonds between them as a driving force. Because the two polymers in the films were drawn very close to each other, the ability of PVA to depress phase transition temperature of copolymer is significantly amplified. As a result, an unprecedented large depression on phase transition temperature was observed. As an example, the phase transition temperature of P­(AAm-DMAA-3-AAPBA)15 is significantly decreased from 86 °C in solution to 14 °C in the LBL film, corresponding to a 72 °C decrease. More importantly, some copolymers that do not exhibit thermosensitive behaviors in solution can be turned to be thermosensitive, as their phase transition temperature can be decreased from ≥100 to <100 °C due to the extraordinarily large ability of PVA to depress the phase transition temperature. Consequently, films from these nonthermosensitive copolymers also present a heat-induced phase transition.

Biological Stimuli-Induced Phase Transition of a Synthesized Block Copolymer: Preferential Interactions between PNIPAM-b-PNVCL and Heme Proteins

“…Proteins vary hydrophobic/hydrophilic interactions, leading to variations in LCST, size ( d H ), and conformational state of the copolymer. A slight discrepancy in LCST was observed for results obtained from thermal fluorescence and DLS measurements, which can be different operational methods for these biophysical techniques. ,, Nonetheless, both techniques give a similar trend in the variation of LCST. The corresponding standard deviations obtained from d H values, LCST values obtained from temperature-dependent fluorescence, and DLS are illustrated in Table S1–S3.…”

Precise Synthesis and Thermoresponsive Property of Poly(ethyl glycidyl ether) and Its Block and Statistic Copolymers with Poly(glycidol)

“…Thus, we conducted the sequential block copolymerization of PBnGE, followed by EGE, using the t-Bu-P 4 /tBBA system with [BnGE] 0 /[EGE] 0 /[tBBA] 0 ratios of 10/90/1, 20/80/1, 30/70/1, 40/60/1, and 50/50/1 to afford a series of PBnGE x -b-PEGE y with various x and y values (Scheme 1 and Table 1). As the first step of block copolymerization, t-Bu-P 4 with a [BnGE] 0 /[tBBA] 0 /[t-Bu-P 4 ] 0 ratio of 50/1/1 catalyzed ROP of BnGE for 20 h. 1 H NMR and SEC analysis of aliquots of the polymer showed that the monomer conversion rate reached 99%, and it was verified that active PBnGE oxyanions were formed, with an M n, NMR value of 8.3 kg mol −1 and M w /M n of 1.04. Then, the block copolymerization second stage was started by adding 50 equivalents of EGE relative to the tBBA used for the first polymerization.…”

“…Aqueous solutions of some polymers show reversible phase-transition behavior, such as white turbidity when heated above the lower critical solution temperature (LCST) and dissolving again to clear when cooled below the LCST [1][2][3]. Such polymers include poly (N-substituted acrylamide)), poly (N-substituted methacrylamide), polyethers, and methyl cellulose [4][5][6][7][8].…”

Aqueous Synthesis of Upper Critical Solution Temperature and Lower Critical Solution Temperature Copolymers through Combination of Hydrogen‐Donors and Hydrogen‐Acceptors

“…Copolymerization has been utilized to create new TRPs from non‐responsive substrates. [ 27 ] Homopolymers of acrylamide (AAm) are freely soluble in water, but copolymers of AAm with hydrophobic comonomers such as acrylonitrile, azobenzene, diaminopyridine, or styrene can have a UCST in aqueous solutions. [ 28–31 ] In contrast, homopolymers of dimethyl acrylamide (DMA) is also water‐soluble, but copolymer of DMA with hydrophobic monomers, such as styrene or phenylacrylamide, exhibit LCST behavior in water.…”