Temperature Responsive Self-Assembly

Temperature-responsive gelation was reported by Hamley for a thermoresponsive amphiphilic copolymer consisting of permanently hydrophobic poly (methyl methacrylate) (PMMA) 

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PHA Phan, H.T.T., Zhu, K., Kjoniksen, A.L., and Nystrom, B., Temperature-responsive self-assembly of charged and uncharged hydroxyethylcellulose-grq/i-poly(A/-isopropylaciylamide) copolymer in aqueous solution. Colloid Polym. Sci., 289, 993, 2011. 

Zareie, H. Boyer, C. Bulmus, V. Nateghi, E. Davis, T. Temperature-responsive self-assembled monolayers of oligo(ethylene glycol) control of biomolecular recognition. ACS Nano 2008, 2, 757-765. 

NAI Naik, S.S., Ray, J.G., and Savin, D.A., Temperature- and pH-responsive self-assembly of poly(propylene oxide)-i-poly(lysine) block copolymers in aqueous solution, Langmuir, 27, 7231, 2011. 

Chuang, C.-Y., Don, T.-M. and Chiu, W.-Y. (2009). Synthesis of chitosan-based thermo- and pH-responsive porous nanoparticles by temperature-dependent self-assembly method and their application in drug release./onma/ of Polymer Science Part A Polymer Chemistry, 47,5126-5136. 

Figure 6.4 Schematic representation of (a) core-shell morphology and (b) temperature-responsive supramolecular self-assembly of arborescent PS-gro/i-P2VP5 copolymers in toluene. (Reprinted with permission from S.I. Yun, G.E. Gadd, V. Lo et al, Temperature-responsive supramolecular assembly of dendrigraft micelles with a solvophilic core -solvophobic shell structure, Macromolecules, 41, 7166-7172. 2008 American Chemical Society.) (Colour version of this figure is available on the book companion web site.)...

Incorporating a temperature-responsive polymer structure in block copolymer architectures provides control over the solubility of a part of the copolymer structure. As such, a double hydrophilic block copolymer consisting of a permanently hydrophilic block and a LCST polymer block is converted into an amphiphilic block copolymer when the solution is heated above the LCST (Figure 22.3). This phenomenon has intrigued polymer scientists and the temperature-induced self-assembly of a large variety of different double hydrophilic thermo-responsive block copolymers into micellar structures has been extensively studied. These results have been captured in a large number of review articles and will not be further addressed here (Gil. and Hudson, 2004 Dimitrova et al., 2007 McCormick et al, 2008 Wei et al, 2009 Rodriguez-Hernandez et al, 2005 Smith et al, 2010). 

The temperature-driven self-assembly of nonionie amphiphilie tailor-made triblock copolymers was studied by DLS, NMR, ITC, and SAXS. The composition of these triblock copolymers is more complex than that of the vast majority of poly(2-allqrl-2-oxazoline)s a statistical thermo-responsive (iPrOx) and hydrophobic (BuOx) central block with terminal hydrophilic blocks (MeOx). Researchers made a first attempt to resolve the effects of each block on nanoparticle formation. The iPrOx/MeOx ratio dets. the value of the cloud point temperature, whereas the different BuOx-iPrOx blocks determine the character of the process. Finally, a study on the thermodynamic and structural profiles of the complexation between these triblock poly(2-allqrl-2-oxazoline)s and two ionic surfactants was presented. 

In systems of LP the dynamic response to a temperature quench is characterized by a different mechanism, namely monomer-mediated equilibrium polymerization (MMEP) in which only single monomers may participate in the mass exchange. For this no analytic solution, even in terms of MFA, seems to exist yet [70]. Monomer-mediated equilibrium polymerization (MMEP) is typical of systems like poly(a-methylstyrene) [5-7] in which a reaction proceeds by the addition or removal of a single monomer at the active end of a polymer chain after a radical initiator has been added to the system so as to start the polymerization. The attachment/detachment of single monomers at chain ends is believed to be the mechanism of equilibrium polymerization also for certain liquid sulphur systems [8] as well as for self-assembled aggregates of certain dyes [9] where chain ends are thermally activated radicals with no initiators needed. 

In principle, the expressions for pair potentials, osmotic pressure and second virial coefficients could be used as input parameters in computer simulations. The objective of performing such simulations is to clarify physical mechanisms and to provide a deeper insight into phenomena of interest, especially under those conditions where structural or thermodynamic parameters of the studied system cannot be accessed easily by experiment. The nature of the intermolecular forces responsible for protein self-assembly and phase behaviour under variation of solution conditions, including temperature, pH and ionic strength, has been explored using this kind of modelling approach (Dickinson and Krishna, 2001 Rosch and Errington, 2007 Blanch et al., 2002). 

Sun Q, Deng Y (2005) Encapsulation of polystyrene latex with temperature-responsive poly(iV-isopropylacrylamide) via a self-assembling approach and the adsorption behaviors therein. Langmuir 21 5812-5816... 

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