Novel AB 2 -type amphiphilic block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide), PEG-b-(PNIPAM) 2 , were successfully synthesized through single-electron transfer living radical polymerization (SET-LRP). A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether (PEG). The copolymers were obtained via the SET-LRP of N-isopropylacrylamide (NIPAM) with CuCl/tris(2-(dimethylamino)ethyl)amine (Me 6 TREN) as catalytic system and DMF/H 2 O (v/v ¼ 3:1) mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography and 1 H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions (PDI \ 1.15). Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry. As a result, the phase transition temperature of PEG 44 -b-(PNIPAM 55 ) 2 is similar to that in the case of PEG 44 -b-PNIPAM 110 ; however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular architecture on the phase transition. This is the first study into the effect of macromolecular architecture on the phase transition using AB 2 -type amphiphilic block copolymer composed of PEG and PNIPAM.

Novel water-soluble triply-responsive homopolymers of N,N-dimethylaminoethyl methacrylate (DMAEMA) containing an azobenzene moiety as the terminal group were synthesized by atom transfer radical polymerization (ATRP) technique. The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2-bromoisobutyryl group (Azo-Br) in the presence of CuCl/Me 6 TREN in 1,4-dioxane as a catalyst system. The molecular weights and their polydispersities of the resulting homopolymers (Azo-PDMAEMA) were characterized by gel permeation chromatography (GPC). The homopolymers are soluble in aqueous solution and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to Ph and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans-to-cis photoisomerization of the azobenzene moiety resulted in a higher LCST, whereas it recovered under visible light irradiation. This kind of polymers should be particularly interesting for a variety of potential applications in some promising areas, such as drug controlled-releasing carriers and intelligent materials because of the multistimuli responsive property.

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Graft copolymers of ethyl cellulose with azobenzene‐containing polymethacrylates were synthesized through atom transfer radical polymerization (ATRP). The residual hydroxyl groups on ethyl cellulose were first esterified with 2‐bromoisobutyryl bromide to yield 2‐bromoisobutyryloxy groups, which was then used to initiate the polymerization of 6‐[4‐(4‐methoxyphenylazo)phenoxy]hexyl methacrylate (MMAzo) in the presence of CuBr/N,N,N′,N″,N″‐pentamethylenetriamine (PMDETA) as catalyst and anisole as solvent. The graft copolymers were characterized by gel permeation chromatography (GPC) and 1H‐NMR. The molecular weights of the graft copolymers increased relatively to the macroinitiator, and the polydispersities were narrow. The thermal and liquid crystalline property of the graft copolymers were investigated by differential scanning calorimeter (DSC) and polarizing optical microscope (POM). Photoresponsive property was studied under the irradiation of UV–vis light in THF solution. The graft copolymers have potential applications, including sensors and optical materials. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1653–1660, 2007

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The mild reaction of the preorganized silsesquioxane precursor with Mn(II) acetate under ambient conditions results in a mixed-valent {Mn II 6 Mn III 4 } nanocage (SD/Mn10) which is protected by both acyclic trimer [Si3] and cyclic tetramer [Si4]. Serendipitous capture of atmospheric CO 2 as a μ 5 -carbonate anion placed at the center supports the formation of the cluster. The magnetic analysis reveals the strong antiferromagnetic interactions between Mn ions. Moreover, the dropcasting film of SD/Mn10 shows photoelectric activity indicating its great potential as a semiconductor for photoelectric conversion applications.