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See detailComparison of Sm complexes with Sn compounds for syntheses of copolymers composed of lactide and cyclic carbonates and their biodegradabilities
Nakayama, Yuushou; Yasuda, Hajime; Yamamoto, Katsuhiro et al

in Reactive & Functional Polymers (2005), 63(2), 95-105

The comparison of organolanthanide complexes, (C5Me5)(2)SmMe(THF) (Sm1) and [(C5Me5)(2)SM](2)(PhC=C=C=CPh) (Sm2), with tin compounds, Bu2Sn(OMe), (Sn1) and Bu2Sn(OCH2CH2CH2O) (Sn2), in the preparation of ... [more ▼]

The comparison of organolanthanide complexes, (C5Me5)(2)SmMe(THF) (Sm1) and [(C5Me5)(2)SM](2)(PhC=C=C=CPh) (Sm2), with tin compounds, Bu2Sn(OMe), (Sn1) and Bu2Sn(OCH2CH2CH2O) (Sn2), in the preparation of random, diblock, and triblock copolymers composed Of L-lactide (L-LA) or D,L-LA and cyclic carbonates, trimethylene carbonate (TMC) or 2,2-dimethyltrimethylene carbonate (DTC) is reported. The biodegradabilities of the resulting copolymers with proteinase K and a compost were examined. The copolymerization of L-LA with cyclic carbonates by Sm1 or Sm2 afforded copolymers with relatively low melting points (< 160 degrees C) due to the accompanying epimerization in comparison with those obtained with Su1 or Sn2. In the degradation of the polymers with a compost, the copolymers based on D, L-LA were more degradable than those based on L-LA. On the other hand, the effect of the incorporated cyclic carbonate on its degradability was more drastic in the copolymers based on L-LA than those in the copolymers based on D, L-LA. The introduction of only a small amount of the cyclic carbonates into PLLA significantly enhanced the degradability of PLLA with a compost or proteinase K. In the enzymatic degradation of L-LA-containing polymers, the copolymerization of L-LA with TMC was also quite effective to improve the degradability of PLLA. Triblock copolymerization tends to be effective to enhance the degradability of PLLA. [less ▲]

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See detailComparison of Sm complexes with Sn compounds for syntheses of copolymers composed of lactide and cyclic carbonates and their biodegradabilities
Yasuda, Hajime; Yamamoto, Katsuhiro; Nakayama, Yuushou et al

in Reactive & Functional Polymers (2004), 61

The comparison of organolanthanide complexes, (C5Me5)(2)SmMe(THF) (Sm1) and [(C5Me5)(2)SM](2)(PhC=C= C=CPh) (Sm2), with tin compounds, Bu2Sn(OMe)(2) (Sn1) and Bu2Sn(OCH2CH2CH2O) (Sn2), in the preparation ... [more ▼]

The comparison of organolanthanide complexes, (C5Me5)(2)SmMe(THF) (Sm1) and [(C5Me5)(2)SM](2)(PhC=C= C=CPh) (Sm2), with tin compounds, Bu2Sn(OMe)(2) (Sn1) and Bu2Sn(OCH2CH2CH2O) (Sn2), in the preparation of random and diblock copolymers composed Of L-lactide (L-LA) or D,L-LA and epsilon-caprolactone (CL), and the preparation of triblock copolymers composed Of L-LA/CL/L-LA was studied and the biodegradabilities of the resulting copolymers with proteinase K and a compost were examined. Poly(L-LA-ran-CL) shows much higher degradability than poly(L-LA) with proteinase K, and poly(L-LA), poly(L-LA-ran-CL) and poly(L-LA-b-CL) (b means block) prepared with Sm1 had better degradability than those synthesized with the Sn1 compound. The degradability Of Poly(L-LA-ran-CL) with proteinase K is higher than that Of poly(L-LA-b-CL). Poly(LA-ran-CL) and poly(LA-b-CL) prepared with Sml revealed higher degradability than those obtained with Sn1 using a compost. Triblock copolymers, poly(L-LA-b-CL-b-L-LA), synthesized with Sm2 revealed nearly the same degradability with those obtained with Sn2 using a compost. Finally, biocompatibility was studied with macrophage activation assay using RAW 264.7, and metabolic viability assay using Cell Titer Aqueous non-radioactive Cell. [less ▲]

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See detailHigh-temperature polyimide nanofoams for microelectronic applications
Hedrick, James L; Carter, K. R.; Cha, J. E. et al

in Reactive & Functional Polymers (1996), 30(1-3), 43-53

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the ... [more ▼]

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term 'nanofoam'. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements. refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach. [less ▲]

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