• Title, Summary, Keyword: Poly(l-lactide)

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Ring-Opening Polymerization of ʟ-Lactide with Polydimethylsiloxane Based Stabilizers in Supercritical Carbon Dioxide (폴리디메틸실록산계 안정화제를 이용한 초임계 이산화탄소에서의 ʟ-Lactide의 개환중합)

  • Hwang, Ha Soo;Lim, Kwon Taek
    • Clean Technology
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    • v.12 no.2
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    • pp.62-66
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    • 2006
  • Poly($\small{L}$-Lactide)(PLLA) was prepared by a ring-opening polymerization of $\small{L}$-Lactide with various polydimethylsiloxane(PDMS) based copolymers as a stabilizer in supercritical carbon dioxide($scCO_2$). The block copolymeric stabilizers were synthesized by group transfer polymerization (GTP) by using PDMS macroinitiator. PLLA was found to be produced with fairly low molecular weight distribution as confirmed by gel permeation chromatography(GPC) analysis. Scanning electron microscopy (SEM) results showed that sub-micron size Poly($\small{L}$-lactide)(PLLA) particles were formed by suspension polymerization.

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Properties and Biodegradability of Polylactide for Paper Coating Application - $Poly(_{L} -lactide)\;and\;Poly(_{D}-lactide)$ Blend -

  • Lim Hyun A;Kang Jin Ha
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.36 no.5
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    • pp.53-61
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    • 2004
  • [ $Poly(_{D}-ldactide)\;(_{D}-PLA)$ ] was synthesized to have low molecular weight for miscible blends with a high molecular $poly(_{L}-lactide)\;(_{L} -PLA)$. The blends were prepared by dissolving the two components of $_{L}-PLA\;and\;_{D}-PLA\;(w/w)$ in chloroform (l00/0, 90/10, 70/30, 50/50, 30/70, 0/100). The miscibility of these miscible blends was characterized by gel-permeation chromatography (GPC), differential scanning calorimetry (DSC), and the selective degradability by enzymes (proteinase K, subtilisin and $\alpha$-chymotrypsin). The coating efficiency of PLA blends onto paper was determined and the degrading activity cellulases by on these blends. The miscibility, coating efficiency and enzymatic degradability of these blends were decreased according to increasing of $_{D}-PLA$ blending part. Such results were attributed to the extent of coating application of PLA, with better miscibility (compatibility), coating efficiency and degradability due to a higher $_{L}-PLA$ content.

Growth of Monolayered Poly(l-lactide) Lamellar Crystals on a Substrate

  • Lee, Won-Ki;Lee, Jin-Kook;Ha, Chang-Sik
    • Macromolecular research
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    • v.11 no.6
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    • pp.511-513
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    • 2003
  • Hydroxyl groups were introduced onto the surface of a silicon wafer by O$_2$ plasma treatment. Poly(l-lactide) (1-PLA) was attached onto the surface-modified silicon wafer by the ring-opening polymerization of l-lactide using the hydroxyl group as an initiator. Lamellar single crystals of 1-PLA were grown directly on the 1-PLA-attached silicon wafer from a 0.025% solution in acetonitrile at 5$^{\circ}C$. A well-separated, lozenge-shaped, monolayered lamellar single crystal was prepared because the 1-PLA-attached silicon wafer acts as an initial nucleus.

Study on Degradation Rates of Biodegradable Polymers by Stereochemistry (입체화학을 이용한 생분해성 고분자의 분해속도에 관한 연구)

  • Park, Chan-Young;Choi, Yong-Hae;Lee, Won-Ki
    • Journal of Environmental Science International
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    • v.18 no.7
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    • pp.797-802
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    • 2009
  • To control degradation rate of biodegradable poly(lactide)s (PLA), the stereochemical PLAs with different ratios of d-lactide and l-lactide units were synthesized by the ring open polymerization and the their degradation kinetics were measured by a Langmuir film balance. The alkaline (pH=11) degradation of poly(l-lactide) (l-PLA) monolayer showed the faster rate at a surface pressure of 4 mN/m in the ranges from to 0 to 7 mN/m. However, the enzymatic degradation of l-PLA with Proteinase K did not occur until 4 mN/m. Above a constant surface pressure of 4 mN/m, the degradation rate was increased with a constant surface pressure. These behaviors might be attributed to the difference in the contacted area with degradation medium: alkaline ions need small contact area with l-PLA while enzymes require much bigger one to be activated due to different medium sizes. The stereochmical PLA monolayers showed that the alkaline degradation was increased with their optical impurities while the enzymatic one was inversed. These results could be explained by the decrease of crystallinity with the optical impurity and the inactivity of enzyme to d-LA unit.

Non-isothermal Crystallization Behavior of Poly(glycolide-co-ε-caprolactone-co-L-lactide) Block Copolymer (생체분해성 Poly(glycolide-co-ε-caprolactone-co-L-lactide) 블록 공중합물의 비등온 결정화 거동에 관한 연구)

  • Choi, Sei-Young;Song, Seung-Ho
    • Elastomers and Composites
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    • v.49 no.1
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    • pp.13-23
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    • 2014
  • In this work, glycolide, L-lactide and ${\varepsilon}$-caprolactone monomers were polymerized into the triblock copolymers by two step polymerization method and their non-isothermal crystallization behaviors were studied by combination of modified Avrami and Ozawa formula for further analysis of their behaviors. The result showed that PGCLA21 gave the highest value for supercooling analysis and super cooling degree increased with L-lactide content. Crystallization velocity constant, however, showed no significant change. The result of cooling function in specific relative crystallization degree showed that the increase of L-lactide content made an effect on the more enhancement of crystallization velocity of the PGCLA than PGCL. The result of big logF(T) value with the L-lactide content above critical point for PGCLA41 and PGCLA21 showed that bigger cooling velocity needed to gain same crystal size compared with PGCL. This means that it gives negative effect in the increase of crystallization velocity.

Degradation Behaviors of Poly(l-lactide) using Model Systems (모델 시스템을 이용한 Poly(l-lactide)의 분해거동)

  • Min Seong-Kee;Moon Myong-Jun;Lee Won-Ki
    • Journal of Environmental Science International
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    • v.15 no.2
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    • pp.177-183
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    • 2006
  • The hydrolytic kinetics of biodegradable poly(l-lactide) (PLLA) have been studied by using two model systems, solution-grown single crystal (SC) and Langmuir monolayer techniques, for elucidating the mechanism for both alkaline and enzymatic degradations. The present study investigated the parameters such as degradation medium and time. The Langmuir mono layers of PLLA showed faster rates of hydrolysis when they were exposed to a basic subphase rather than they did when exposed to neutral subphase. Both degradation mediums had moderate concentrations to show a maximized activity, depending on their sizes. An alkaline degradation of SCs of PLLA showed the decrease of molecular weight of the remained crystals due to the erosion of chain-folding surface. However, the enzymatic degradation of SCs of PLLA occurred in the crystal edges thus the molecular weight of remained crystals was not changed. This behavior might be attributed to the size of enzymes which is much larger than that of alkaline ions; that is, the enzymes need larger contact area with monolayers to be activated.

Electrospun Nanofibers of Poly(L-lactide)/Rod-like Hydroxyapatite Composites (전기방사에 의한 Poly(L-lactide)/막대형 Hydroxyapatite 복합체 나노섬유의 제조)

  • Park, Doo Jin;Choi, Youngeun;Cho, Se Youn;Jin, Hyoung-Joon
    • Textile Science and Engineering
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    • v.49 no.4
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    • pp.195-199
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    • 2012
  • Rod-like hydroxyapatites (HAs) were successfully fabricated with $CaCl_2$, $Na_2HPO_4$, and polyvinylpyrrolidone (PVP) as a stabilizer. FT-IR was used to identify rod-like HA and to observe the functional groups on the surface of HA. We conducted the turbiscan test to confirm the effects of the HA ratio on the dispersion stability in the chloroform/acetone mixture. A 3D scaffold for bone tissue regeneration was produced by electrospinning poly(L-lactide) (PLLA) with 2, 5, and 10 wt% of rod-like HAs. SEM, TEM, and XRD showed that rod-like HAs were well-embedded into the electrospun PLLA nanofibers and the mechanical properties of PLLA and PLLA/HA nanofibers were measured by UTM. Pure PLLA nanofibers had higher tensile strength than PLLA/HA nanofibers. Furthermore, 2 and 5 wt% of HAs-incorporated PLLA nanofibers showed increased Young's modulus compared to pure PLLA nanofibers because of the hardness of HA and the strong interaction between PLLA and HA by hydrogen bonds.

Synthesis and Properties of A-B-A Type Block Copoly(ester-ether) Comprising Poly(L-lactic acid) (A) and Poly(oxyethylene) (B) (Poly(L-lactic acid)와 Poly(oxyethylene)의 A-B-A 블록공중합체 합성과 그 특성)

  • 이찬우
    • Textile Science and Engineering
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    • v.34 no.3
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    • pp.143-147
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    • 1997
  • An A-B-A block copoly (ester-ether) comprising poly(L-lactic acid) (A) and poly (oxyethylene) (B) was prepared by copolymerization of L-lactide and a commercially available telechelic polymer, polyethylene glycol (PEG), with different molecular weights by the catalysis of triethyl aluminium/toluene. The molecular weight and the unit composition were successfully controlled by changing the L-lactide/PEG ratio in feed. DSC curves of the copolymers are ascribed to the endothermic peak with PEG segment and exothermic peak by PLLA segment. There is a tendency that melting temperature ($T_m$) reduced with increasing PEG composition. These results suggested that the PEG segments and PLLA are compatible and homogeneously mixed in the amorphous phase of PLLA without forming a microphase separation in the solid state. The compatibility of both polymers, however, would not be so high as to prevent crystallization of PLLA. It was found that the copolymer films showed an improved flexibility due to the incorporation of the soft PEG segment. The in vitro hydrolysis test of the films showed that the block copolymer has much higher degradability than the homo poly(L-lactic acid)

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Synthesis of Lactide from Oligomeric PLA: Effects of Temperature, Pressure, and Catalyst

  • Yoo, Dong-Keun;Kim, Duk-Joon;Lee, Doo-Sung
    • Macromolecular research
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    • v.14 no.5
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    • pp.510-516
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    • 2006
  • Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

Synthesis and Biodegradability of Block Copolymer Comprising Poly(L-lactic acid) and Poly(oxypropylene) for Medical Suture (의료용 봉합사로서 Poly(L-lactic acid)/Poly(oxypropylene)을 포함한 블록 공중합체의 합성 및 생분해성)

  • 이찬우;오세화
    • Textile Science and Engineering
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    • v.35 no.1
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    • pp.1-7
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    • 1998
  • The A-B-A block copolymers were prepared by the ring opening polymerization of L-lactide by the polypropylene glycol (PPG; Mw/Mn=1.1, Mn=4000) with $Me_3Al-H_2O$ as the catalyst. When the feed ratios of PPG were over 5 and 10 wt% relative to L-lactide, the polymerization of L-lactide took place from the PPG hydroxyl terminals to give the desired A-B-A block copolymers in high yields. The resulting molecular weights were in good agreement with the values estimated from the monomer conversions and the feed ratios of PPG. At the lower feed ratios of PPG, the poly(L-lactic acid) (PLLA) homopolymer was formed along with the block copolymers. The block copolymers were melt-spun by the conventional method and the fibers obtained were extended by drawing at $60^{\circ}C$. At the same draw ratio, the modulus of the fibers was decreased with increasing PPG content in the block copolymers. The fibers of the PLLA-PPG-PLLA block copolymers with different contents of PPG were subjected to degradation in vitro. Upon immersion in a phosphate buffer solution (pH=7.4), the fibers showed a time-dependent decrease in tensile strength with accompanying surface erosion. The degradation rate of this fiber was much higher than that of PLLA fiber. It was therefore suggested that the block copolymers comprising PLLA and PPG, have high potential as the biodegradable suture with improved flexibility and biodegradability.

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