Stereospecific Polymerization of β-Alkyl-β-propiolactone

Teranishi, Kiyoshi; Iida, Makoto; Araki, Takeo; Yamashita, Shinsuke; Tani, Hisaya

doi:10.1021/ma60040a005

Cited by 96 publications

(35 citation statements)

References 5 publications

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“…Diethylzinc/water (ZnEt 2 / H 2 O) (1/0.6) catalyst was prepared by a reported method. 35 ZnEt 2 was allowed to react with deoxygenated water at a molar ratio of 1/0.6 (ZnEt 2 /H 2 O) in dry 1,4-dioxane, followed by freeze-drying of the reaction mixture. The obtained ZnEt 2 /H 2 O was used as a catalyst for non-end-capped PLLA.…”

Section: Methodsmentioning

confidence: 99%

Structural Effects of Terminal Groups on Nonenzymatic and Enzymatic Degradations of End-Capped Poly(l-lactide)

et al. 2008

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Poly(L-lactide) (PLLA) with various alkyl ester chain end groups were synthesized by ring-opening polymerization of L-lactide in the presence of zinc alkoxide as a catalyst. The structural effect of chain end groups on the rate of enzymatic and nonenzymatic degradations for amorphous films of PLLA were investigated at 37 degrees C in a Tris-HCl buffer solution (pH 8.6) with proteinase K and at 60 degrees C in a phosphate buffer solution (pH 7.4), respectively. The rate of enzymatic degradation for PLLA films was dependent on the carbon numbers of alkyl ester chain end groups, and the rates of PLLA samples with dodecyl (C12), tridecyl (C13), and tetracocyl (C14) ester end groups were much lower than those of the other samples. The surface morphologies of PLLA films after enzymatic degradation were characterized by scanning electron microscopy. After the enzymatic degradation, non-end-capped PLLA, PLLA with methyl (C1) and hexyl (C6) ester chain ends, were degraded homogeneously by proteinase K and the film surface was very smooth. In contrast, the PLLA with alkyl ester chain ends of carbon numbers over 12 were degraded heterogeneously by the enzyme, and the sponge-like network structure was formed on the film surface. These results indicated that the long alkyl ester groups at the chain ends of PLLA molecules aggregated in the amorphous films and the erosion rate was depressed due to the coverage of the aggregated terminal groups on the film surface. For the nonenzymatic degradation, the molecular weight of non-end-capped PLLA was remarkably decreased with progress of degradation. In contrast, the molecular weight of the end-capped PLLA gradually reduced at the initial stage of degradation and then the rate of degradation was accelerated. The decreases of molecular weight of PLLA by autocatalyzed degradation were retarded by the capping of carboxyl chain ends.

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Section: Methodsmentioning

confidence: 99%

Structural Effects of Terminal Groups on Nonenzymatic and Enzymatic Degradations of End-Capped Poly(l-lactide)

et al. 2008

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“…Diethylzinc/water (ZnEt 2 /H 2 O) (1/0.6) catalyst was prepared by a reported method. 21 ZnEt 2 was reacted with deoxygenated water at a molar ratio of 1/0.6 (ZnEt 2 /H 2 O) in dry 1,4-dioxane (distilled over Na), followed by freeze-drying of the reaction mixture. A yellow powder was obtained and used as a catalyst.…”

Section: Methodsmentioning

confidence: 99%

Synthesis, Solid-State Structure, and Surface Properties of End-Capped Poly(l-lactide)

et al. 2004

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End-capped poly(L-lactide) (PLLA) samples with dodecyl or 2-(2-(2-methoxyethoxy)ethoxy)ethyl (MEEE) ester were synthesized by ring-opening polymerization of L-lactide in the presence of zinc dodecanoxide or zinc 2-(2-(2-methoxyethoxy)ethoxy)ethoxide as a catalyst, respectively. On the basis of NMR analysis, it was confirmed that the carboxylic acid chain ends of PLLA molecules were selectively substituted by dodecyl or MEEE ester groups. To evaluate the wettability on the surface of end-capped PLLA films, the advancing contact angle (thetaa) with water was measured. The amorphous PLLA films showed relatively similar thetaa values regardless of the chemical structure of the polymer chain end. In contrast, the thetaa values of semicrystalline films were varied over a wide range, dependent on the chemical structure of the chain end. In addition, the thetaa values of dodecyl ester end-capped PLLA film with low molecular weight increased with an increase in the crystallization temperature. Both the crystallinity and lamellar thickness of dodecyl ester end-capped PLLA films increased with the crystallization temperature. These results suggest that the segregation of the chain ends on the PLLA film surface was strongly affected by the crystallization conditions.

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“…In later years alkylaluminoxanes were scarcely used in the polymerization of aldehydes [11,12], oxetane [13,14], cyclic esters [10,[15][16][17][18][19][20][21] and cyclic carbonates [22][23][24], in the copolymerization of carbon dioxide with oxiranes [25] and oxetane [26], as well as in the copolymerization of olefins or styrene with acrylic monomers [27]. However, these reactions did not find wider practical application due to the high cost of catalysts and problems with the obtaining of aluminoxanes of reproducible structure and activity.…”

Section: Introductionmentioning

confidence: 99%