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PCL Segments (pcl + segment)

Distribution by Scientific Domains

Polymers and Materials Science	100%

Selected Abstracts

Relationship between morphology structure and composition of polycaprolactone/Poly(ethylene oxide)/Polylactide copolymeric microspheres

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2002
Guangming Li
Abstract A novel tri-component copolymer, polycaprolactone/poly(ethylene oxide)/polylactide (PCEL) was synthesized. The effect of the chemical composition on physical properties was investigated by using NMR, differential scanning calorimetry (DSC) and X-ray diffraction. Both the soft segment poly(ethylene oxide) (PEO) and polycaprolactone (PCL) could enhance the mobility of polymer chains and decrease the crystallizability of the copolymers. The polymeric microspheres, which are of interest for drug delivery systems, were prepared using an emulsification-solvent evaporation technique. By scanning electron microscopy (SEM) and atomic force microscopy (AFM), the surface morphology of the microspheres was studied. It was found that the presence of PEO segment could improve the hydrophilicity of the copolymers and the morphology of the polymeric microspheres could be altered by adjusting the chemical composition. The accumulation of PEO segments on the outer surface of the polymeric microspheres was proven by X-ray photoelectron spectroscopy (XPS). It had also been proven that the PCL segment could facilitate the movement of PEO segment to the outer surface. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Simultaneous reversible addition fragmentation chain transfer and ring-opening polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008
Maude Le Hellaye
Abstract The simultaneous ring-opening polymerization (ROP) of ,-caprolactone (,-CL) and 2-hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ,-CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2-ethylhexanoate (Sn(Oct)2) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA- g -PCL. Graft copolymer formation is evidenced by a combination of size-exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000,10,000 g mol,1) the copolymer grafting density is higher than 90%. The ratio of free HEMA-PCL homopolymer produced during the "one-step" process was found to depend on the HEMA concentration, as well as the half-life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058,3067, 2008 [source]

Poly(ester urethane)s with polycaprolactone soft segments: A morphological study

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002
Juliana Kloss
Abstract Two series of poly(ester urethane)s were prepared, containing polycaprolactone (PCL) as the soft segment with molecular weights of 530 and 2000. In each series, the soft-segment/hard-segment ratio was varied, and the morphological changes were monitored with differential scanning calorimetry, dynamic mechanical thermal analysis, wide-angle X-ray scattering, and scanning electron microscopy techniques. The polyurethanes with longer PCL segments retained their crystallinity, whereas those with shorter PCL segments did not. A morphological model is proposed, in which a continuous PCL-rich matrix contains both PCL crystallites and domains of urethane hard segments. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4117,4130, 2002 [source]

Synthesis, Sequential Crystallization and Morphological Evolution of Well-Defined Star-Shaped Poly(, -caprolactone)- b -poly(L -lactide) Block Copolymer,

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2006
Jing-Liang Wang
Abstract Summary: Well-defined star-shaped poly(, -caprolactone)- b -poly(L -lactide) copolymers (PCL- b -PLLA) were synthesized via sequential block copolymerization, and their molecular weights and arm length ratio could be accurately controlled. Both differential scanning calorimetry and wide angle X-ray diffraction analysis indicated that the crystallization of both the PLLA and PCL blocks within the star-shaped PCL- b -PLLA copolymer could be adjusted from the arm length of each block, and both blocks mutually influenced each other. The sequential isothermal crystallization process of both the PLLA and PCL blocks within the PCL- b -PLLA copolymers was directly observed with a polarized optical microscope, and the isothermal crystallization of the PCL segments was mainly templated by the existing spherulites of PLLA. Moreover, the PLLA blocks within the star-shaped PCL- b -PLLA copolymer progressively changed from ordinary spherulites to banded spherulites when the arm length ratio of PCL to PLLA was increased while concentric spherulites were observed for the linear analog. Significantly, these novel spherulites with concentric or banded textures and the morphological evolution of the spherulites have been observed for the first time in the PCL- b -PLLA block copolymers. [source]