Baimark Y, Molloy R, Molloy N, Siripitayananon J, Punyodom W, Sriyai M
Biomedical Polymers Technology Unit, Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand.
J Mater Sci Mater Med. 2005 Aug;16(8):699-707. doi: 10.1007/s10856-005-2605-6.
This paper describes the synthesis and characterization of a block copolymer of L-lactide (LL) and epsilon -caprolactone (CL) and its subsequent melt spinning into a monofilament fiber. The synthesis reaction was a two-step process. In the first step, an approximately 50:50 mol% random copolymer, P(LL-co-CL), was synthesized via bulk copolymerization of LL and CL. This first-step prepolymer then became the macroinitiator in the second-step reaction in which more LL monomer was added to form a block copolymer, PLL-b-P(LL-co-CL)-b-PLL. Both the prepolymer and block copolymer were characterized by a combination of analytical techniques comprising dilute-solution viscometry, GPC, 1H and 13C NMR, DSC and TG. The block copolymer was then processed into a monofilament fiber using a small-scale melt spinning apparatus. The fiber was spun with a minimum amount of chain orientation and crystallinity so that its semi-crystalline morphology could be constructed under more controlled conditions in subsequent off-line hot-drawing and annealing steps. In this way, the fiber's tensile properties and dimensional stability were developed, as indicated by the changes in its stress-strain curve. The final drawn and annealed fiber had a tensile strength (>400 MPa) approaching that of a commercial PDS II suture of similar size. It is considered that this type of block copolymer has the potential to be developed further as a lower-cost alternative to the current commercial monofilament surgical sutures.
本文描述了L-丙交酯（LL）和ε-己内酯（CL）的嵌段共聚物的合成与表征，以及随后将其熔融纺丝制成单丝纤维的过程。合成反应是一个两步过程。第一步，通过LL和CL的本体共聚合成了一种摩尔比约为50:50的无规共聚物P(LL-co-CL)。然后，这种第一步的预聚物在第二步反应中成为大分子引发剂，在该反应中加入更多的LL单体以形成嵌段共聚物PLL-b-P(LL-co-CL)-b-PLL。预聚物和嵌段共聚物均通过包括稀溶液粘度法、凝胶渗透色谱法（GPC）、1H和13C核磁共振波谱法（NMR）、差示扫描量热法（DSC）和热重分析法（TG）在内的多种分析技术进行表征。然后使用小型熔融纺丝设备将嵌段共聚物加工成单丝纤维。纺丝时使纤维具有最小量的链取向和结晶度，以便在随后的离线热拉伸和退火步骤中在更可控的条件下构建其半结晶形态。通过这种方式，纤维的拉伸性能和尺寸稳定性得到了改善，这在其应力-应变曲线的变化中得到了体现。最终经过拉伸和退火的纤维的拉伸强度（>400 MPa）接近类似尺寸的商业PDS II缝线的拉伸强度。据认为，这种类型的嵌段共聚物有潜力作为当前商业单丝手术缝线的低成本替代品得到进一步开发。
