Poly block copolymer, gelation

These poly(MMA) obtained could induce the photopolymerization of St to give a star block copolymer, butgelation was partly observed, similar to thepoly-merization of St with 51. The addition of 13 in the photopolymerization of MA with 51 was effective in preventing gelation [175]. 

This category includes such polymers as atactic polystyrene (25-291 or poly(vinylchloride) (30.31 and references therein). A closely related problem is the gelation of non-block copolymers (5), which share with atactic polymers the feature that chemically and conformationally homogeneous sequences may be relatively short, so that when two or more chains interact, large crystalline domains are prevented from forming. 

This chapter is concerned with experiments and theory for semidilute and concentrated block copolymer solutions.The focus is on the thermodynamics, i.e. the phase behaviour of both micellar solutions and non-micellar (e.g. swollen lamellar) phases. The chapter is organized very simply Section 4.2 contains a general account of gelation in block copolymer solutions. Section 4.3 is concerned with the solution phase behaviour of poly(oxyethylene)-containing diblocks and tri-blocks. The phase behaviour of styrenic block copolymers in selective solvents is discussed in Section 4.4. Section 4.5 is then concerned with theories for ordered block copolymer solutions, including both non-micellar phases in semidilute solutions and micellar gels. There has been little work on the dynamics of semidilute and concentrated block copolymer solutions, and this is reflected by the limited discussion of this subject in this chapter. 

Li SM, Vert M. Synthesis, characterization, and stereocomplex-induced gelation of block copolymers prepared by ringopening polymerization of L(d)-lactide in the presence of poly(-ethylene glycol). Macromolecules 2003 36 8008-8014. 

Jeong B, Lee DS, Shon J-i, Bae YH, Kim SW. Thermoreversible gelation of poly(ethylene oxide) biodegradable polyester block copolymers. J Polym Sci A 1999 37 751-760. 

Jeong et al. studied the gelation behavior of poly(ethylene glycol)-h-poly(L-alanine) (PEG-h-L-PA) block copolymers in water [117, 118]. They suggested that the P-sheet structure of l-PA plays a critical role in developing a fibrous nanostructure as well as in the sol-to-gel transition of the copolymer solutions (Fig. 14). The conformation of l-PA in water is random coil at low concentrations. As the concentration increases, block copolymers start to aggregate and the conformation... 

Furthermore, addition of hydrophobic ibuprofen resulted in a collapse of all of the gels. The latter is analogous to the findings by Scherlund et al. on the temperature-induced gelation of PEO-PPO-PEO block copolymers on addition of lidocaine and prilocaine in their base forms (see Figure 1.14), as well as to the findings by Carlsson et al. on pH-dependent reductions of the cloud points of poly(A -isopropyl acrylamide) solutions on addition of either lidocaine or prilocaine (215). 

Amphiphilic block copolymers have attracted great interest in biomaterials apphcalions. Erom micelle formation to thermally induced gelation, these amphiphilic block copolymers find interesting applications in drug delivery and tissue engineering. Poly(ethylene... 

Attwood, D., Tait, C.J. and Collett,J.H. (1987) Thermally reversible gelation characteristics, poly(oxyethy-lene)-poly(oxypropylene) block copolymer in aqueou.s solution after exposure to high-energy irradiation (Chapter 10), in Controlled-Release Technology Pharmaceutical Applications, Lee P.I., and Good, W. (eds), American Chemical Society, Washington D.C. 

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