Polymers with Upper Critical Solution Temperature in Aqueous Solution

Abstract

This review focuses on polymers with upper critical solution temperature (UCST) in water or electrolyte solution and provides a detailed survey of the yet few existing examples. A guide for synthetic chemists for the design of novel UCST polymers is presented and possible handles to tune the phase transition temperature, sharpness of transition, hysteresis, and effectiveness of phase separation are discussed. This review tries to answer the question why polymers with UCST remained largely underrepresented in academic as well as applied research and what requirements have to be fulfilled to make these polymers suitable for the development of smart materials with a positive thermoresponse.

One-pot synthesis of responsive sulfobetaine nanoparticles by RAFT polymerisation: the effect of branching on the UCST cloud point

“…al. 4 The same group has reported several examples of the previously unnoticed UCST behaviour of well-known polymer systems such as poly(acrylamide-co-acrylonitrile) 5 and poly(N- 35 acryloyl glycinamide); 6 however few other examples exist. Polybetaines are electrically neutral polymers that contain both cationic and anionic groups within a single monomer unit.…”

Recognition‐Mediated Hydrogel Swelling Controlled by Interaction with a Negative Thermoresponsive LCST Polymer

“…[21] Thea rea of thermoresponsive hydrogels is largely dominated by LCST systems, [22][23][24] whereby poly(N-isopropylacrylamide) (PNIPAM)-based hydrogels are the most common systems,a st hey undergo as harp phase transition close to physiological temperatures (around 32 8 8C). [25] In contrast, UCST-type thermoresponsive hydrogels are much less developed, [26][27][28][29] even though hydrogen-bonding UCST polymers seem very promising for biomedical applications. [30] Theg oal of the present study was to develop ah ydrogel system that undergoes abrupt swelling upon heating (positive thermoresponse) while remaining hydrophilic in both the contracted and expanded states.W ed esigned as upramolecular hydrogel system featuring an on-thermoresponsive poly(N,N-dimethylacrylamide) hydrogel functionalized with dialkoxynaphthalene guest units (NaphtGel;F igure 1a)t hat significantly swells upon complexation with the tetracationic cyclophane host cyclobis(paraquat-p-phenylene) (CBPQT…”

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

“…This may be attributed to the fact, that the transitions are seldom observed for practically relevant conditions 27 . Few recent examples of polymers exhibiting UCST based on thermally reversible hydrogen bonding (HB-UCST) in water include poly(N-acryloylglycinamide) (PNAGA) and its derivatives 27,28 , poly(allylurea) copolymers 29 and copolymers of N-vinylimidazole and 1-vinyl-2-(hydroxylmethyl)imidazole 30 . In the past, systems based on poly(methyl methacrylate), PMMA 31 , poly(2-oxazolines) 32 and copolymers of hydroxyethyl methacrylate and acetoacetoxyethyl methacrylate in ethanol/water mixtures have also demonstrated the UCST-behaviour.…”