Types of thermo-responsive polymers

A-substituted acrylamides are an extensive class of thermo-responsive polymers that have attracted a lot of interest due to their unique thermo-responsive behavior in aqueous media. Among this class, poly(A -isopropylacrylamide) (PNIPAAm) is the most extensively studied polymer for structure activity relationships (Bae, Okano, Kim, 1990 Feil, Bae, Feijen, Kim, 1992) and potential thermo-responsive apphcations. 

Poly vinylcaprolactam (PVCL) ELP Poly (Glycine-Valine-Glycine-Valine-Proline) 

Reproduced with permission from Galaev and Mattiasson (1993). 

Raucher, 2002 Kirsh, 1998 Schild Tirrell, 1990). Incorporation of hydrophilic or hydrophobic co-monomers with these polymers has also been reported to influence the LCST (Beckman, Amighi, Moes, 2001 Beckman, Moes, Amighi, 2002 Mikheeva et al., 1997). Moreover, the LCST of PNIPAAm and PVCL polymers were decreased in the presence of salts (Beckman et al., 2001,2002 Mikheeva et al., 1997 Schild Tirrell, 1990) and other polar solvents such as alcohol (Kirsh, 1998), acetone, and dioxane (Costa Freitas, 2002 Schild, Muthukumar, Tirrell, 1991 Wu, Liu, Heng, Yang, 2005). The incorporation of proteins in polymer solution of PNIPAAm led to increased hydrophobic interactions and increased the LCST values. 

Simulation studies have been used by researchers to analyze hydrogen bond formation dynamics and molecular distribution in solution. There are reports carried out with systems that have large numbers of polymer chains in solution, and in systems that have smaller numbers of isolated polymer linear chains in solution. It has been 

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Figure 1.6 Micelles generated by different types of thermo-responsive polymers in aqneous solutions. Block copolymers with hydrophobic blocks flanked by hydrophUic blocks.

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