Thermoresponsive hydrogel

Thermoresponsive polymers based on oligo(ethylene glycol) acrylates or methacrylates can be easily prepared by atom transfer radical polymerization under straightforward experimental conditions (i.e. in bulk or in ethanol solution and in the presence of commercially available catalysts). Thus, these stimuli-responsive macromolecules can be exploited for preparing a wide range of smart advanced materials such as thermoreversible hydrogels, thermoresponsive block-copolymer micelles and switchable surfaces. Hence, some of the results... 

Bioconjugate Synthesis—Stage 1. As described above, we have already demonstrated our ability to produce thermoresponsive copolymer hydrogel particles that possess groups for protein attachment. 

Blood compatibility of PEG-modified surfaces was discussed in terms of the mobility of water molecules at the interface of hydrogel materices. The property and application of poly(N-isopropylacrylamide) and its copolymers as thermoresponsive hydrogel were also reviewed. 

In contrast to these approaches based on nonspecific interactions, Zhang and coworkers described a molecularly imprinted hydrogel based on the ther-moresponsive PNIPAM [184], This hydrogel was prepared by copolymerization of a metal chelate monomer iV-(4-vinyl)-benzyl iminodiacetic acid, which formed a coordination complex with the template protein in the presence of Cu ions, A-isopropylacrylamide, acrylamide, and IV.lV-methylenebisacrylamide as crosslinker. The interaction of the imprinted thermoresponsive hydrogel with the protein could be switched between coordination effects and electrostatic attraction by addition or omission of Cu ions. Furthermore, this imprinted hydrogel allowed switching of lysozyme adsorption by changing the temperature. 

The thin NIPAAm hydrogel layers were covalently attached to the surface, therefore the swelling was confined to one direction perpendicular to the substrate. The degree of anisotropy was calculated from ratio of l/0p and swelling ratio. This ratio was found to be between 1.2-1.3. Such a study describing the effect of hydrophilic comonomer on Tc of PNIPAAm provides an opportunity to formulate thermoresponsive hydrogel layers with desired transition temperature and swelling behavior for various applications. 

Thermal Thermoresponsive hydrogel Change in temperature, change in polymer-polymer and water-polymer interactions, change in swelling, release of drug... 

Li SK and D Emanuele A. On-off transport through a thermoresponsive hydrogel composite membrane. J. Control. Rel. 2001 75 55-67. 

Akiyoshi, K. Deguchi, S. Tajima, H. Nishikawa, T. Sunamoto, J. Microscopic structure and thermoresponsiveness of a hydrogel nanoparticle by self-assembly of a hydrophobized polysaccharide. Macromolecules 1997, 30, 857-861. 

Among stimuli-responsive or thermoresponsive polymer microspheres, poly(N-isopropylacrylamidc) (PNIPA) was investigated most intensively. Cross-linked PNIPA is a thermosensitive hydrogel which undergoes a volume phase transition at its lower critical solution temperature (LCST) of around 34 °C. Several authors reported the synthesis of PNIPA microspheres [68-73]. 

Schild HG, Muthukumar M, Tirrell DA (1991) Cononsolvency in mixed aqueous-solutions of poly (W-isopropyacrylamide). Macromolecules 24 948-952 Schmaljohann D, Nitschke M, Schulze R, Eing A, Werner C, Eichhom K-J (2005) In situ study of thermoresponsive behavior of micropattemed hydrogel films by imaging ellipsometry. Langmuir 21 2317-2322... 

Yoshioka H, Mikami M, Mori Y, Tsuchida E (1993) Preparation of thermoresponsive surfaces using polyvinylchloride-graft-poly(A-isopropylacrylamide). Polym Adv Technol 4 519-521 Yu H, Grainger DW (1993) Thermosensitive swelling behavior in cross.linked N-isopropylacry-lamide networks-cationic, anionic, and ampholytic hydrogels. J Appl Polym Sci 49 1553-1563... 

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