Homopolymers, thermoresponsive

Due to the relative ease of control, temperature is one of the most widely used external stimuli for the synthesis of stimulus-responsive bmshes. In this case, thermoresponsive polymer bmshes from poly(N-isopropylacrylamide) (PNIPAM) are the most intensively studied responsive bmshes that display a lower critical solution temperature (LOST) in a suitable solvent. Below the critical point, the polymer chains interact preferentially with the solvent and adopt a swollen, extended conformation. Above the critical point, the polymer chains collapse as they become more solvophobic. Jayachandran et reported the synthesis of PNIPAM homopolymer and block copolymer brushes on the surface of latex particles by aqueous ATRP. Urey demonstrated that PNIPAM brushes were sensitive to temperature and salt concentration. Zhu et synthesized Au-NPs stabilized with thiol-terminated PNIPAM via the grafting to approach. These thermosensitive Au-NPs exhibit a sharp, reversible, dear opaque transition in solution between 25 and 30 °C. Shan et al. prepared PNIPAM-coated Au-NPs using both grafting to and graft from approaches. Lv et al. prepared dual-sensitive polymer by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide from trithiocarbonate groups linked to dextran and sucdnoylation of dextran after polymerization. Such dextran-based dual-sensitive polymer is employed to endow Au-NPs with stability and pH and temperature sensitivity. 

In this section we outline the publications and selected features of neutral thermoresponsive homopolymers exhibiting the LCST phase separation in aqueous media, see Tables 2 and 3, and also those whose properties drastically change upon cooling, see Table 4. We will utilize the definitions for transition temperatures used by the authors. Due to the huge number of polymers of this type, some biopolymers such as polysaccharides will not be described here. 

Table 2 Neutral thermoresponsive homopolymers exhibiting LCST-type phase separation behaviour in water...

Polyi v mylether)s °- o3-r 33 X Polyether is a polymer with oxygen atoms in the main or side chtiin. Among them, thermoresponsive poly(vinylether)s have oxymethylene and/or oxyethylene pendants in their side chains [30, 124,404-406] Phase separation temperature of vinyl ethers can be controlled by varying the number of the pendant oxyethylene units and/or the hydrophobicity of an co-alkyl group, R Tcp measurements typically reveal an abrupt reversible transition within AT = 1°C no hysteresis Homopolymers of ethyl vinylether and higher alkyl vinylethers are insoluble in water... 

Table 4 Neutral thermoresponsive homopolymers, for which the solubility in water decreases upon cooling...

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