Modulation of reversible self-assembling of dumbbell-shaped poly(ethylene glycol)s and β-cyclodextrins: precipitation and heat-induced supramolecular crosslinking
(893-900) Polymer Journal 43 #11 (2011)
Abstract
Kobayashi et al of the Japan Advanced Institute of Science and Technology,, Japan, prepared a series of dumbbell-shaped poly(ethylene glycol) (PEG) chains attached to bulky end groups.  Some of the chains formed supramolecular assemblies with β-cyclodextrin (β-CD) and its multiple, ditopic and tetratopic, derivatives. The chains with proper end groups successfully allowed β-CD to be trapped onto PEG through formation of hydrogen bonds at room temperature and higher. Mixing of the PEG chain and the ditopic supramolecular crosslinker in water at 40 °C led to a change in solution property from viscous to elastic, accompanied by a significant increase in viscosity, whereas this change was not induced at room temperature. A supramolecular network formed only when the PEG chain was mixed with the tetratopic supramolecular crosslinker at 40 °C. Once formed, the supramolecular crosslinking was maintained even after the system cooled down.  (RDC 11/11/2011)

Synthesis and properties of a polyrotaxane network prepared from a Pd-templated bis-macrocycle as a topological cross-linker
(909-915) Polymer Journal 43 #11 (2011)
Abstract
Ogawa et al Tokyo Institute of Technology, Japan, synthesized polyrotaxane networks (PRNs) by exploiting a Pd-templated bis-macrocycle as a topological cross-linker during radical polymerization of a vinyl monomer.  The bis-macrocycle was prepared by combining two macrocycles with a linear linker. Radical polymerization of 4-vinylpyridine in the presence of the bis-macrocycle and a catalytic amount of 2,2′-azobisisobutyronitrile (AIBN) yielded a gelled polymer.  The addition of 4-tert-butylstyrene as a vinyl co-monomer to the polymerization system afforded a sufficiently stable gel as the PRN, clearly indicating that 4-tert-butylstyrene was successfully introduced as end-capping moieties of the trunk polymer.  The swelling properties of the PRN were evaluated using several solvents. (RDC 11/11/2011)