可生物降解PLA／PCL,PELA／PECL共混体系的研究

本工作以DSC研究了聚d,l-乳酸/聚ε-己内酯(PLA/PCL)、聚d,l-乳酸-聚乙二醇嵌段共聚物/聚ε-己内酯-聚乙二醇嵌段共聚物(PELA/PECL)共混体系的相容性,发现PLA/PCL体系是不相容的,随PLA含量的增大,PCL结晶度增大。而PELA/PECL共混体系中,由于PEG链段的“内增容作用”,使二组分有较好的相容性。随PELA含量的增加,PECL的熔点、结晶度降低。     

PEG改性聚乳酸嵌段共聚物降解性能研究

辛酸亚锡催化下开环聚合制备聚乳酸(DL-PLA)-聚乙二醇(PEG)-聚乳酸三嵌段共聚物.用GPC、DSC、1 H-NMR、质量损失、静态接触角等方法在pH=7.4磷酸盐缓冲液中,37℃下研究了分子量Mn=400、1000和4000的PEG改性DL-PLA的降解行为.结果表明,PEG嵌段增强了共聚物的亲水性,降低了共聚物Tg,加速了共聚物降解,随着PEG分子量增加及两端DL-PLA链段增长,共聚物分子量下降速率加快.由研究结果得出,共聚物降解期间DL-PLA链段中的酯键随机断裂,PEG两端DL-PLA链段逐渐变短;降解后期DL-PLA链段进一步变短,并有短链DL-PLA均聚物产生,当PEG两端DL-PLA链段足够短时,共聚物在介质中溶解.     

PCL-b-PMMA/PEO共混薄膜的微相分离形貌

通过聚氧化乙烯(PEO)与聚己内酯-聚甲基丙烯酸甲酯嵌段共聚物(PCL-b-PMMA)的共混来调节聚己内酯(PCL)与聚甲基丙烯酸甲酯(PMMA)嵌段的微相分离行为。采用原子力显微镜研究了PEO的质量分数和相对分子质量对PCL-b-PMMA/PEO共混薄膜微相分离形貌的影响。结果表明,共混薄膜形成了以PMMA/PEO为连续相,PCL呈柱状微区垂直于薄膜表面的微相分离形貌,PMMA/PEO链段无法在PCL柱状微区上方形成完全覆盖,导致薄膜表面形成许多孔洞。随着PEO含量增加,PCL链段聚集趋势增强,柱状微区尺寸不断增大;随着PEO相对分子质量的增加,PMMA/PEO在PCL微区上方形成的有效覆盖减少,薄膜表面的孔洞数量和尺寸增大;当PEO与不同嵌段比PCL-b-PMMA共混后,随嵌段共聚物中PCL链段体积分数增加,柱状微区向层状形态转变,薄膜表面孔洞消失。     

含立构复合晶体的聚己内酯形状记忆弹性体的制备及性能

以聚己内酯(PCL)、左旋丙交酯(LLA)、右旋丙交酯(DLA)为原料,以辛酸亚锡(Sn(Oct)_2)为催化剂,合成了不同LA含量的P(LLA-b-CL)和P(DLA-b-CL)嵌段共聚物。用凝胶渗透色谱、核磁共振等研究了嵌段共聚物的组成与结构。将2种嵌段共聚物按一定比例溶液共混,并通过流延法得到PCL基形状记忆弹性体薄膜,研究了其结晶性能、晶体形态、力学性能及形状记忆性能。结果表明,随LA添加量增大,弹性体薄膜中的PLLA与PDLA形成的立构复合(SC)晶体结晶度增大;同时,PLA非晶区含量提高,70℃拉伸时PLA链段产生滑移,形状回复率降低。因此,弹性体中SC晶体的结晶度越高,形状回复率越高,形状回复率最佳可达93.54%。     

聚羟基烷酸酯与聚丙烯酸丁酯复合材料的相容性及生物降解性能研究

研究了用液相和固相反应性共混使聚丙烯酸丁酯 (PBA)与羟基丁酸 戊酸共聚物(PHBV)复合后 ,其接枝率和均聚物含量对复合物相容性、结晶性和生物降解性的影响 ,比较了不同试样在土壤中降解后的重量损失和形貌变化 ,结果表明PBA的接枝不利于PHBV的结晶和生物降解性 ,当PHBV PBA含量比为 6 0 4 0时 ,接枝率下降和均聚物含量增加至 2 0 4 % ,导致复合物两相明显不溶 ,土壤中降解后重量损失大大下降 ,而且微生物对PHBV PBA的侵蚀仅仅发生在表面PHBV相中     

嵌段共聚物PCL-b-PMMA薄膜的微相分离形貌

通过开环聚合(ROP)和原子转移自由基聚合(ATRP)制备了不同嵌段结构的嵌段共聚物PCL-b-PMMA,使用核磁共振(1H-NMR)和凝胶渗透色谱(GPC)对其结构进行了表征,通过原子力显微镜(AFM)研究了嵌段共聚物薄膜的微相分离形貌。结果表明,嵌段共聚物发生了微相分离,聚ε-己内酯(PCL)链段形成柱状微区;PCL链段体积分数较低时,薄膜表面以聚甲基丙烯酸甲酯(PMMA)链段聚集为主,但未在PCL柱状微区上方形成覆盖,从而在薄膜表面形成孔洞;随PCL链段体积分数增加及PMMA链段分子量下降,PCL柱状微区面积增加,向薄膜表面迁移并逐渐形成覆盖,造成薄膜表面孔洞消失。     

聚偏氟乙烯均聚物和共聚物的结晶行为研究

通过研究PVDF均聚物和PVDF与六氟丙烯的共聚物的结晶行为,来掌握与六氟丙烯共聚后,PVDF结晶行为的变化.研究结果表明,在结晶过程中,均聚物和共聚物都形成具有球晶结构的α晶型.相比于均聚物,共聚物的结晶(熔融)温度、平衡熔点和结晶度均下降.两种聚合物在等温结晶时,随着结晶温度提高,结晶速率下降.在相同的过冷度下,共聚物的结晶速率低于均聚物.     

对二氧环己酮/己内酯嵌段共聚物的合成与表征

采用三乙基铝(ALEt3)引发ε-己内酯开环聚合成为大分子引发剂,然后加入不同量的对二氧环己酮(PDO)合成出具有不同共聚物组成和分子量的聚己内酯／对二氧环己酮二嵌段共聚物(P(CL-bPDO))。采用。H-NMR、DSC、GPC、TG测试等分析手段表征了共聚物的结构和性能。结果表明,共聚物保留各自均聚物的一些性能。从共聚物的DSC曲线上可以看到两个分别与PCL链段和PPDO链段对应的熔融峰,热重分析表明,共聚物分两个阶段分解,第一阶段为PPDO的分解,第二阶段为PCL的分解。     

两亲性生物降解羟丙基纤维素-聚己内酯接枝共聚物在蛋白药物微胶囊中的应用

以溶菌酶为蛋白模型,用复乳化和溶剂蒸发技术制备了微米级可生物降解的羟丙基纤维素-接枝-聚己内酯共聚物(HPC-g-PCL)/蛋白药物微胶囊。运用红外光谱(FT-IR)确定了所制备微囊中HPC-g-PCL和溶菌酶的存在;差示扫描量热(DSC)分析结果表明,HPC-g-PCL包裹溶菌酶蛋白后,结晶能力降低,结晶更加不完善,致使熔点下降;扫描电镜(SEM)观察结果表明,HPC-g-PCL微囊呈球形结构,但是与PCL均聚物微囊相比,表面呈现凹凸结构和明显的粒状突起。初步判断为HPC-g-PCL共聚物的两亲性本质所致。     

聚羟基烷酸酯与聚丙烯酸丁酯复合材料的相容性及生物降解性能研究

研究了用液相和固相反应性共混使聚丙烯酸丁酯（PBA）与羟基丁酸－戊酸共聚物（PHBV）复合后，其接枝率和均聚物含量对复合物相容性，结晶性和生物降解性的影响，比较了不同试样在土壤中降解后的重量损失和形貌变化，结果表明PBA的接枝不利于PHBV的结晶和生物降解性，当PHBV／PBA含量比为60／40时，接枝率下降和均聚物含量增加到20．4％，导致复合物两相明显不溶，土壤中降解后重量损失大大下降，而且微生物对PHBV／PBA的侵蚀仅仅发生在表面PHBV相中。     

Hydrolytic degradation of PCL/PEO copolymers in alkaline media

PCL/PEO copolymers with different compositions were obtained from ring opening polymerization of -caprolactone in the presence of ethylene oxide and characterized by various analytical techniques. Data collected from DSC and X-ray diffractometry suggested that the copolymer chains possess a blocky structure, leading to both PCL and PEO-type crystalline structures. Hydrolytic degradation of these copolymers was carried out in a pH=10.6 carbonate buffer solution at 37 °C. Comparison was made with a PCL homopolymer and a PCL/PEG blend which had the same gross composition as one of the copolymers. The results showed that the presence of PEO sequences considerably enhanced the hydrophilicity of the copolymers as compared with PCL homopolymer. Nevertheless, the degradability of PCL chains was not enhanced due to the phase separation between the two components. These materials should be of great interest for biomedical uses such as matrices for sustained drug delivery because of the presence of both hydrophilic and hydrophobic microdomains. ©2000 Kluwer Academic Publishers     

Structural and morphological changes in Poly(caprolactone)/poly(vinyl chloride) blends caused by UV irradiation

Films made from a blend of poly(ε-caprolactone) and poly(vinyl chloride) (PCL/PVC) retained high crystallinity in a segregated PCL phase. Structural and morphological changes produced when the films were exposed to high potency ultraviolet (UV) irradiation for 10 h were measured by UV-Vis spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). They were different to those observed with homopolymer PCL and PVC films treated under the same conditions. The FTIR spectra of the PCL/PVC blend suggest that blending decreased the susceptibility of the PCL to crystallize when irradiated. Similarly, although scanning electron micrographs of PCL showed evidence of growth of crystalline domains, particularly after UV irradiation, the images of PCL/PVC were fairly featureless. It is apparent that the degradation behavior is strongly influenced by the interaction of the two polymers in the amorphous phase.     

The role of crystallinity on differential attachment/proliferation of osteoblasts and fibroblasts on poly(caprolactone-co-glycolide) polymeric surfaces

The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly(caprolactone-co-glycolide) (PCL/PGA) polymers. PCL/PGA polymers were selected since they reflect both highly crystalline and amorphous materials. PCL/PGA polymeric materials were fabricated by compression molding into thin films. Five compositions, from PCL or PGA to intermediate copolymeric compositions of PCL/PGA in ratios of 25:75, 35:65 and 45:55, were studied. Pure PCL and PGA represented the crystalline materials while the copolymers were amorphous. The polymers/copolymers were characterized using DSC to assess crystallinity, contact angle measurement for hydrophobicity, and AFM for nanotopography. The PCL/PGA films demonstrated similar hydrophobicity and nanotopography whereas they differed significantly in crystallinity. Cell adhesion to and proliferation on PCL/PGA films and proliferation studies were performed using osteoblasts and NIH-3T3 fibroblasts. It was observed that highly crystalline and rigid PCL and PGA surfaces were significantly more efficient in supporting fibroblast growth, whereas amorphous/flexible PCL/PGA 35:65 was significantly more efficient in supporting growth of osteoblasts. This study demonstrated that while chemical composition, hydrophobicity and surface roughness of PCL/PGA polymers were held constant, crystallinity and rigidity of PCL/PGA played major roles in determining cell responses.     

淀粉接枝共聚物在淀粉/聚乳酸共混体系中的作用

研究了淀粉／聚乳酸共混体系的相容性，考察了淀粉－聚醋酸乙烯酯和淀粉－聚乳酸接枝共聚物对淀粉／聚乳酸共混体系相容性的影响。发现上述两种接枝共聚物均可有效地增加淀粉与聚乳酸的相容性，从而提高共混体系的耐水性的力学性能。     

不同成膜工艺对PCL结晶及微生物降解性能的影响

将压延成膜和溶剂成膜制备的聚ε-己内酯(PCL)膜放入降解液进行100d的生物降解,以研究不同成膜工艺对PCL降解性和降解前后结晶的影响。采用显微镜观察降解前后薄膜表面形态变化;通过广角X射线衍射法(WAXD)表征其降解前后结晶变化;利用凝胶渗透色谱(GPC)测定降解过程中PCL相对分子质量和分子量分布的变化。研究结果表明,溶剂成膜工艺可提高PCL亲水性,增大结晶尺寸,提高PCL降解性;而压延成膜工艺使膜表面致密,结晶尺寸减小,但对结晶形态和结晶度影响不大,降解后PCL晶形均未发生大的变化,结晶度有所下降。     

酪氨酸改性聚乳酸共聚物的合成及降解研究

以乳酸(D,L-LA)和L-酪氨酸(Tyr)为原料[n(D,L-LA)/n(Tyr)=95/5],氯化亚锡(Sn(cl)2)为催化剂,采用梯度升温法,通过直接熔融缩聚合成聚(乳酸-酪氨酸)共聚物(PLA-co-Tyr).用特性粘度测试、FT-IR、1 H-NMR、GPC、DSC、XRD、TG等对其进行表征,通过SEM、XRD等方法研究了降解前后材料的表面形态、结晶度及失重率的变化.结果表明:系列共聚物中的重均相对分子量Mw最大可达2900,与聚乳酸相比具有较小的Tg和结晶度,分解温度高于180℃,具有良好热稳定性且降解性能优于聚乳酸.     

Alkaline degradation study of linear and network poly(ε-caprolactone)

Alkaline hydrolysis of a polycaprolactone (PCL) network obtained by photopolymerization of a PCL macromer was investigated. The PCL macromer was obtained by the reaction of PCL diol with methacrylic anhydride. Degradation of PCL network is much faster than linear PCL; the weight loss rate is approximately constant until it reaches around 70%, which happens after approximately 60 h in PCL network and 600 h in linear PCL. Calorimetric results show no changes in crystallinity throughout degradation, suggesting that it takes place in the crystalline and amorphous phases simultaneously. Scanning electron microscopy microphotographs indicate that degradation is produced by a different erosion mechanism in both kinds of samples. The more hydrophilic network PCL would follow a bulk-erosion mechanism, whereas linear PCL would follow a surface-erosion mechanism. Mechanical testing of degraded samples shows a decline in mechanical properties due to changes in sample porosity as a consequence of the degradation process.     

Tetracycline hydrochloride (TCH)-loaded drug carrier based on PLA:PCL nanofibre mats: experimental characterisation and release kinetics modelling

The experimental characterisation of electrospun poly(lactic acid) (PLA):poly(ε-caprolactone) (PCL) as drug carriers, at five blend ratios from 1:0, 3:1, 1:1, 1:3 and 0:1, was holistically investigated in terms of their morphological structures, crystallinity levels and thermal properties. A widely used antibiotic tetracycline hydrochloride (TCH) was loaded to prepared fibrous mats at TCH concentrations of 1 and 5 wt%. The additional TCH into PLA:PCL better facilitates the reduction of fibre diameter than polymer blends. Increasing the TCH concentration from 1 to 5 wt% was found to result in only a modest decrease in the crystallinity level, but a significant increase in the crystallisation temperature (T _c) for PLA within PLA:PCL blends. The infrared spectra of fibre mats confirm the successful TCH encapsulation into fibrous networks. The first order and Zeng models for drug release kinetics were in better agreement with experimental release data, indicating the release acceleration of TCH with increasing its concentration. In a typical case of PLA:PCL (1:1) loaded with 5 wt% TCH, the fibre mats apparently demonstrate more wrinkled and floppy structures and increased fibre diameters and decreased inter-fibrous spaces after 7-day in vitro fibre degradation, as opposed to those obtained after 3-h degradation.     

Nanospheres prepared from poly(β-malic acid) benzyl ester copolymers: evidence for their in vitro degradation

The in vitro degradation of nanospheres perpared from three benzyl ester derivatives of poly (-malic acid) containing 80, 90 and 100% of benzylated malic acid units was studied. The progressive decrease in the molecular weight of the copolymers was observed as the nanospheres degraded, demonstrating that the degradation under the experimental conditions occurred by a simple hydrolytic cleavage of the ester bond between the monomeric units. The degradation was slow, with the weight average molecular weight decreasing to about 70% of the initial value in 5 months for all the nanosphere systems. A comparison of degradation rates for benzyl ester copolymers with the degradation rate of poly (-malic acid) homopolymer demonstrated a decreased degradation rate of benzylated copolymers which suggests that the introduction of a pendent benzyl ester function in proximity to the ester bond in the main chain, reduces the rate of the bond cleavage. No significant difference in the degradation behaviour of highly benzylated copolymers, containing 90 and 80% of benzylated malic acid units, and fully benzylated polymer could be detected to prove an autocatalytic role on degradation of the free pendent carboxyl group in the former two copolymers.