• Macromolecular Research
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• 제14권5호
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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.

• 폴리머
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• 제37권5호
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• pp.606-612
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• 2013

$Al(O-i-Pr)_3$을 촉매로 이용하고 중합 개시제로 glycidol을 사용하여 L-lactide를 개환중합하여 glycidol-poly(lactide)(Gly-PLA)를 얻었다. $^1H$ NMR 분석 결과 glycidol의 말단에 존재하는 수산기가 Gly-PLA에는 존재하지 않았고 이를 통해 glycidol의 말단에 존재하는 OH기가 개시제의 역할을 하여 중합이 진행되었음을 확인하였다. Llactide용액중합과 벌크중합을 진행하였으며, L-lactide/glycidol 몰비, 중합 온도와 시간에 따라 생성된 Gly-PLA의 분자특성을 관찰하였다. L-lactide/glycidol 몰비가 증가할수록 수율과 분자량은 증가하였다. 또한 L-lactide/glycidol 몰비가 증가할수록 저분자량에 해당하는 낮은 녹는점 피크는 줄어들고, 고분자량에 해당하는 높은 녹는점 피크가 증가하였다.

• 한국환경과학회지
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• 제23권3호
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• pp.473-481
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• 2014

Poly(lactide)s(PLA) is an attractive material to solve the problem of waste plastic accumulation in nature because of its biodegradability. The lactide exists in three stereoisomeric configurations: L-lactide, D-lactide, and meso-lactide. PLA stereocomplexes, formed by the mixing of two enantiomers, poly(L-lactide)(PLLA) and poly(D-lactide)(PDLA), have many favorable characteristics because the stereocomplex showed $50^{\circ}C$ higher melting point than each enantiomeric polymer and the resistance toward degradation increased. In this study, we investigated the influence of the composition and the optical purity of each component on the formation of stereocomplexes. Also, the nanofibers of stereochemical PLA and their blends were prepared by electrospinning method. The properties of the obtained fibers were analyzed by differential scanning calorimetry and scanning electron microscopy. The results showed that a degree of stereocomplex was controlled by change of optical purity of each component. The enzymatic degradation of the fibers were strongly dependent on the stereocomplex.

• Elastomers and Composites
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• 제49권1호
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• pp.13-23
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• 2014

본 연구에서는 생체분해성 폴리에스터 계열의 glycolide, L-lactide 및 ${\varepsilon}$-caprolactone 단량체를 이용하여 2단계 중합법에 의한 삼원 공중합체를 제조하여, DSC를 이용한 비등온 결정화 거동을 고찰하였다. 보다 더 정확한 거동을 검토하기 위하여 Avrami 식과 Ozawa 식을 조합하여 비등온 결정화 거동을 고찰하였다. 과냉각도를 분석한 결과 PGCLA21의 값이 가장 큰 값을 보이고 있으며 L-lactide 함량이 증가함에 따라 과냉각도는 증가하는 경향을 보이고 있다. 수정된 Avrami 식을 이용하여 다양한 냉각속도에서 비등온 결정화 거동 결정화 속도 상수는 큰 경향을 보이고 있지 않는 것을 알 수 있었다. Avrami 및 Ozawa 식을 조합하여 특정한 상대적 결정화도에서의 냉각함수를 구한결과 L-lactide 함량이 증가하면서 PGCL과 비교시 결정화 속도를 향상시키는 역할을 하고 있는 것으로 여겨지는 반면 PGCLA41과 PGCLA21을 비교시 L-lactide 함량이 일정 이상 증가시 logF(T) 값이 큰 것을 확인 할 수 있는데 이는 동일한 결정을 얻는데 더 많은 냉각 속도를 필요로 한다는 것을 의미하며 결정화 속도 향상에 부정적인 영향을 미치는 것으로 판단된다.

• 대한화학회지
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• 제34권2호
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• pp.203-210
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• 1990

의약 전달체에 사용되는 생체분해성 고분자로서 L-lactic acid 와 L-glutamic acid가 각기 다른 조성비로 이루어진 공중합체를 합성하였다. Poly (L-lactide)는 zink oxide를 이용하여 합성하였으며, Poly (L-lactide) 말단에 3-Amino-l-propanol을 도입시킨 다음 이미 합성된 γ-benzyl-L-glutamate-N-carboxyanhydride (γ-BLG-NCA)를 개환중합시켜서 block copoly (L-lactide-γ-benzyl-L-glutamate)를 합성하였다. NMR로써 L-lactide와 γ-BLG-NCA가 서로 일정한 비율로 이루어진 공중합체가 합성되었음을 확인하였으며, 생성된 공중합체들의 열적성질은 시차주사열량계법 및 열무게 측정법으로 조사하였다.

• 멤브레인
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• 제15권4호
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• pp.281-288
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• 2005

생체 적합성이 우수한 히아루론산과 생분해성이 우수한 폴리 락타이드의 이량체를 결합하여 약물 방출 시스템에 적용할 수 있는 생체 재료를 제조하고자 하였다. 냉동 건조법을 이용하여 히아루론산과 락타이드를 가교제 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC)로 가교시켰다. 생성된 막을 핵자기 공명 분광법으로 분석하여 락타이드 반응도와 EDC 반응도를 결정하였다. 히아루론산에 대한 락타이드 몰비, 가교제 농도가 증가할수록 혹은 가교 온도가 감소할수록, 락타이드 반응도가 증가하였으며 팽윤도는 감소하였다. 서로 다른 락타이드 반응도를 가진 막으로 약물 방출 실험을 수행한 결과 락타이드 반응도가 증가하면 약물 방출 속도가 감소하는 경향을 보였다. 또 친수성이 다른 여러 가지 약물로 약물 방출 실험을 수행한 결과 친수성이 우수한 약물일수록 서서히 방출되었다.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 춘계학술발표대회
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• pp.550-553
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• 2000

The polymeric matrices made with poly(D,L-lactide-co-glycolide) were prepared using copolymer of poly(D,L-lactide) and poly(ethylene glycol) for application of drug delivery systems. Catalyst made use of stannous actoate. Particle size were differ greatly$(435.3{\pm}11.2{\sim}2284.1{\pm}188.5)$ that nanoparticle made use of according to solvent of various kinds. Polymer could a sharp distinction with copolymerized among LE-1, LE-2 and LE-3 of PLA and PEG of content that to examine $^1H-NMR$ of copolymer make refine and reprecipitation. Drug delivery effect at PLGA nanoparticle : PLA amount more then proved highly drug delivery amount that each LE-1, LE-2, LE-3, drug and solvent was 40mg, 20mg and 10mg. Drug delivery effect proved higher 20mg that change(10mg, 20mg, 40mg) at drug feeding amount with LE-2. The first a lot of drug proved delivery. LE-3 most lactide content proved much delivery since biodegradable on PLGA copolymer result from lactide. Also biodegradable rate was highest at LE-3 much of lactide content, because influence at biodegradable effect of lactide by inclusive of soft PEG.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.622-624
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• 2003

Poly(lactic acid) is a biodegradable themoplastic based on the renewable resources to substitute for petrochemical plastics. Most of PLA is produced by ring opening polymerization from lactide. However, pyrolysis process in the lactide synthesis is expensive, we studied lactide synthetic process for more economical preparation of PLA. In this research was tried to minimize the pyrolysis time, and obtained L-lactide from lactic acid without any catalyst.

• 한국염색가공학회지
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• 제10권2호
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• pp.29-36
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• 1998

Poly(L-lactide) microcapsules containing hydrophilic penetrate were prepared by interfacial precipitation method through solvent evaporation from w/o/w emulsion. Effect of four determinative process parameters on the particle size distributions, morphologies, and release properties of microcapsules coated with poly(L-lactide) was investigated. Moreover, susceptible functional cotton fabrics treated with the mentioned microcapsules were prepared and laundry test up to 15 times were done to determine fastness properties. As a result, the prepared poly(L-lactide) microcapsules with a more sharp-distributive, rounder, and more permeable membranes could be prepared by means of protective colloid concentration, solution volume and stirring rate.

• Macromolecular Research
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• 제9권2호
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• pp.84-91
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• 2001

Both A-B-A triblock and multiblock copoly(ester-ether)s consisting of poly(L-Lactide) and poly(oxyethylene-co-oxypropylene) were prepared and characterized. The preparation of the triblock copolymer was done by ring-opening copolymerization of L-lactide with a commercially available telechelic copolyether, Pluronic$\^$TM/(PN) by catalysis of stannous octanoate. The molecular weight and unit composition of the produced copolymers were successfully controlled by changing the L-lactide/PN ratio in feed. However, a high molecular weight copolymer incorporating PN in large amount was not obtained because the molecular weight of the resulting copolymer was limited at a high L-lactide/PN composition. The multiblock copolymer was synthesized by the copolycondensation of oligo(L-lactic acid) prepared by thermal dehydration of L-lactic acid, PN, and dodecanedioic acid as carboxyl/hydroxyl adjusting agent. This polycondensation proceeded by catalysis of stannous oxide to give multiblock copolymers with high molecular weight and wide range of compositions.