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Star-shaped Poly (star-shaped + poly)
Selected AbstractsProtein-Release Behavior of Self-Assembled PEG,, -Cyclodextrin/PEG,Cholesterol HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Frank van de Manakker Abstract This paper reports on the degradation and protein release behavior of a self-assembled hydrogel system composed of , -cyclodextrin- (,CD) and cholesterol-derivatized 8-arm star-shaped poly(ethylene glycol) (PEG8). By mixing ,CD- and cholesterol-derivatized PEG8 (molecular weights 10, 20 and 40 kDa) in aqueous solution, hydrogels with different rheological properties are formed. It is shown that hydrogel degradation is mainly the result of surface erosion, which depends on the network swelling stresses and initial crosslink density of the gels. This degradation mechanism, which is hardly observed for other water-absorbing polymer networks, leads to a quantitative and nearly zero-order release of entrapped proteins. This system therefore offers great potential for protein delivery. [source] Synthesis, crystallization, and morphology of star-shaped poly(,-caprolactone)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005Jing-Liang Wang Abstract Six-arm star-shaped poly(,-caprolactone) (sPCL) was successfully synthesized via the ring-opening polymerization of ,-caprolactone with a commercial dipentaerythritol as the initiator and stannous octoate (SnOct2) as the catalyst in bulk at 120 °C. The effects of the molar ratios of both the monomer to the initiator and the monomer to the catalyst on the molecular weight of the polymer were investigated in detail. The molecular weight of the polymer linearly increased with the molar ratio of the monomer to the initiator, and the molecular weight distribution was very low (weight-average molecular weight/number-average molecular weight = 1.05,1.24). However, the molar ratio of the monomer to the catalyst had no apparent influence on the molecular weight of the polymer. Differential scanning calorimetry analysis indicated that the maximal melting point, cold crystallization temperature, and degree of crystallinity of the sPCL polymers increased with increasing molecular weight, and crystallinities of different sizes and imperfect crystallization possibly did not exist in the sPCL polymers. Furthermore, polarized optical microscopy analysis indicated that the crystallization rate of the polymers was in the order of linear poly(,-caprolactone) (LPCL) > sPCL5 > sPCL1 (sPCL5 had a higher molecular weight than both sPCL1 and LPCL, which had similar molecular weights). Both LPCL and sPCL5 exhibited a good spherulitic morphology with apparent Maltese cross patterns, whereas sPCL1 showed a poor spherulitic morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5449,5457, 2005 [source] Supramolecular inclusion complexes of star-shaped poly(,-caprolactone) with ,-cyclodextrinJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Lu Wang Abstract Both star-shaped poly(,-caprolactone) (PCL) having 4 arms (4sPCL) and 6 arms (6sPCL) and linear PCL having 1 arm (LPCL) and 2 arms (2LPCL) were synthesized and then investigated for inclusion complexation with ,-cyclodextrin (,-CD). The supramolecular inclusion complexes (ICs) were in detail characterized by 1H NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray diffraction, solid-state carbon nuclear magnetic resonance spectroscopy using cross-polarization and magic-angle spinning, and Fourier transform infrared, respectively. The stoichiometry (CL:CD, mol:mol) of all ICs increased with the increasing branch arm of PCL polymers, and it was in the order of ,-CD-6sPCL1 ICs > ,-CD-4sPCL ICs > ,-CD-2LPCL ICs > ,-CD-LPCL ICs. All analyses indicated that the branch arms of star-shaped PCL polymers were included into the hydrophobic ,-CD cavities and their original crystalline properties were completely suppressed. Moreover, the ICs of star-shaped PCL with ,-CD had a channel-type crystalline structure similar to that formed between the linear PCL and ,-CD. Furthermore, the thermal stability of the free PCL polymers probably controlled that of the guest polymers included in the ICs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4721,4730, 2005 [source] Synthesis and characterization of optically active star-shaped poly (N -phenylmaleimide)s with a calixarene corePOLYMER INTERNATIONAL, Issue 6 2007Liping Lou Abstract Two N -phenylmaleimide derivatives bearing a chiral oxazoline group, N -[o -(4-phenyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(R)-PhOPMI] and N -[o -(4-isopropyl-4,5-dihydro-1,3-oxazol-2-yl)phenyl]maleimide [(S)-PriOPMI], were polymerized using in situ generated calixarene-based phenates as initiators to yield optically active polymers. The formation of star-shaped architectures was strongly dependent on both polymerization conditions and calixarene moieties. In the case of polymerization conducted in toluene at 80,100 °C, the arm-chain numbers achieved their respective maxima for the polymers with these multifunctional initiators. In contrast, the polymers obtained in polymerizations at lower temperature possessed fewer arm chains. The structure and chiroptical properties were investigated on the basis of 13C NMR, multiangular laser light scattering, gel permeation chromatography, and circular dichroism for the macromolecules with calixarene cores. Copyright © 2006 Society of Chemical Industry [source] | ||||||||||