Cross-linking thermoreversible

Polymers with a sizable number of ionic groups and a relatively nonpolar backbone are known as ionomers. The term was first used for copolymers of ethylene with carboxylated monomers (such as methacrylic acid) present as salts, and cross-linked thermoreversibly by divalent metal ions. Such polymers are useful as transparent packaging and coating materials. Their fluorinated forms have been made into very interesting ion-exchange membranes (considered further below). 

These physical cross-links are, in general, not permanent and may disappear on swelling or increase in temperature. The corresponding networks are referred to as "physical" or "thermoreversible" and are not considered in this chapter. The reader may refer to Burchard and Ross-Murphy [17-19] for further information on such materials. 

Peng C-C, Abetz V. A simple pathway toward quantitative modification of polybutadiene a new approach to thermoreversible cross-linking rubber comprising supramolecular hydrogen-bonding networks. Macromolecules 2005 38 5575-5580. 

Modification of macromolecular material properties by hydrogen bond formation has been demonstrated at the example of thermoreversible networks Stadler modified poly(butadiene) elastomers with urazole groups to introduce hydrogen-bonded cross-links into the system. In fact, thermoreversible cross-linking appeared due to the urazol-urazole molecular recognition, causing intermolecular cross-links [408,467]. The group of Meijer expanded the approach by the synthesis of two... 

Corresponding DLS and rheology studies to prove the validity of the Eq. (18) were performed on another thermoreversible system (three mixtures made of xanthan gum and locust bean gum (XG/LBG) (Richter et al. 2004b, 2005) and on the irreversibly radical chemical cross-linking system (W-vinylcaprolactam/ 2-hydroxylethyl- methacrylate/allylmethacrylate) (Richter et al. 2004c). 

Takeda M, Norisuye T, Shibayama M (2000) Critical dynamics of cross-linked polymer chains near the gelation threshold. Macromolecules 33 2909-2915 Te Nijenhuis K (1997a) Thermoreversible networks. Introduction. Adv Polym Sci 130 1-12 Te Nijenhuis K (1997b) Thermoreversible networks. Gelatin. Adv Polym Sci 130 160-193 Theiss D, Schmidt T, Dorschner H, Reichelt R, Arndt K-F (2005) Filled temperature-sensitive poly(vinyl methyl ether) hydrogels. J Appl Polym Sci 98 2253-2265 Toomey R, Freidank D, Riihe J (2004) Swelling behavior of thin, surface-attached polymer networks. Macromolecules 37 882-887... 

Another type of behavior is obtained with thermoreversible gels like agarose. Electron microscopy has shown that the network structure of these gels consists of fibers made from many polymer chains. In such gels, elasticity doesn t come from the entropy of the chains, as in the case of covalently cross-linked polymers, but from the mechanical bending elasticity of the fibers. The elastic moduli are about 10 times larger than those of entropic... 

Sim, C. X., van der Mee, A. ]., Goossens, J. G. R, and van Duin, M. 2006. Thermoreversible cross-linking of maleated ethylene/ propylene copolymers using hydrogen-bonding and ionic interactions. Macromolecules 39 3441-3449. 

Polymer types that can be formulated into FRRPP-based homogeneous nanospheres for medical applications include thermoreversible hydrogels, such as linear and cross-linked copolymers based in methacrylic acid, n-isopropyl acrylamide (NIPAM), vinyl alcohol from vinyl acetate. Nanospheres from more conventional polymers, such as polystyrene, can be used as model materials as well. It should be noted that nanoparticles are of the same size as viruses thus, they are all capable of generating or becoming viruses themselves. It is important to accompany studies of formation and application of nanoparticles for medical applications with studies based on less complicated model materials. 

Thermoreversible gels with multiple cross-linking... 

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