聚乳酸的成型加工及其降解性能

研究了可生物降解材料－－聚乳酸（PLLA）的流变性能、纺丝成型性能及降解性能,发现PLLA熔体为切力变稀流体,非牛顿指数n=0.93,具有良好的挤出成型性能。同时,通过PLLA纤维和薄膜在不同环境中的降解实验,表明聚乳酸是一种良好的生物降解医用材料和环保塑料。     

纳米SiO_2对聚乳酸薄膜阻隔性的影响

采用熔融共混法,向聚左旋乳酸(PLLA)分别加入亲水性和疏水性SiO_2对其进行改性。采用差示扫描量热分析仪(DSC)、透氧仪和透湿仪对PLLA/SiO_2薄膜的热学性能和阻隔性能进行了研究。结果表明,亲水SiO_2或疏水SiO_2的加入,使PLLA薄膜的结晶度有所提高,同时阻氧性有所降低,说明虽然SiO_2分散相使PLLA薄膜的结晶度提高,但团聚状态的SiO_2使PLLA薄膜缺陷增多,当后者占优时薄膜阻隔性就会降低。此外,只有加入较高含量的疏水性SiO_2时才能使PLLA薄膜的阻湿性能有所提高。     

PBAT/PLLA共混薄膜的热学、力学及阻透性能

采用熔融共混法制备聚对苯二甲酸己二酸丁二醇酯（PBAT）和L聚乳酸（PLLA）共混薄膜,探讨不同PLLA添加量（质量分数分别为10 %、20 %、30 %）对共混薄膜力学性能、热学性能、气体阻透性能的影响。结果表明,PBAT和PLLA共混属于不相容体系;随着PLLA的添加,共混薄膜的O2和CO2透过性能逐渐降低;当PLLA含量增加到30 %时,O2 透过系数(PO2)和CO2透过系数(PCO2)分别较PBAT薄膜降低了34.2 %和70.8 %,CO2/O2透过比（PCO2/PO2）由纯PBAT的10.20降低为4.52,提高了薄膜阻透性能;PLLA的添加改善了PBAT极易变形变曲现象。     

聚（乳酸⁃乙醇酸）薄膜制备及其性能研究

以左旋乳酸（L?LA）和乙醇酸（GA）为原料,利用一步法熔融共聚合成聚（乳酸?乙醇酸）（PLLGA）共聚物,通过差示扫描量热仪（DSC）对共聚物薄膜的结晶性能进行了表征,并利用Avrami方程对其进行了等温结晶动力学研究,通过万能拉伸试验机和压差法气体透过仪对共聚物薄膜的力学性能和气体阻隔性能进行测试。结果表明,PLLGA共聚物薄膜中GA的引入对材料结晶性能有较大影响,在GA含量为4 %（摩尔分数,下同）的PLLGA中,GA表现为成核剂作用,共聚物结晶比纯聚左旋乳酸（PLLA）薄膜快,半结晶时间减少;而在GA含量为8 %的PLLGA中,GA则表现出限制分子链运动的作用,破坏共聚物分子间的规整度,导致材料结晶性能大幅度降低,处于非晶态;随着GA含量的增加,PLLGA薄膜的拉伸强度和弹性模量逐步下降,而断裂伸长率大幅度增加,GA含量为8 %的PLLGA的断裂伸长率达到了130.1 %,是纯PLLA薄膜的21.3倍;同时,PLLGA薄膜的气体阻隔性显著增加,5 ℃时,相比于纯PLLA薄膜,GA含量为8 %的PLLGA薄膜的O₂、CO₂、N₂透过量分别降低了47 %、41 %和39 %。     

基于{SbW_9}夹心结构构筑多金属氧簇研究进展

三缺位单元构筑的金属氧簇化合物拓宽了多酸化学的发展方向,丰富了多金属氧簇在催化、磁性能方面的应用。{SbW_9}是一种三缺位构筑基本单元,通过引入过渡金属、稀土金属、有机物及有机金属基团实现共价键作用力、离子键或非共价键作用力修饰,得到结构多样、性能优异的新型簇化合物,但针对{SbW_9}夹心结构构筑多金属氧簇综述类研究鲜有报道。总结了已报道的111例基于{SbW_9}单元构筑的多金属氧簇化合物,对其结构、合成策略及影响因素进行分析,简述其在催化、磁性、生物医药等方面的应用,并对{XW_9}缺位单元构筑多金属氧酸盐的发展前景进行了展望。该综述对结构拓展、高核簇构建具有一定意义。     

高柔性PLLA/PBF共混膜的制备及性能

为改善高柔性聚乳酸(PLLA)的力学性能，采用聚乳酸为原料，将其与不同质量比例的聚富马酸丁二酯(PBF)共混，制备出聚乳酸/聚富马酸丁二酯(PLLA/PBF)共混薄膜。对PLLA/PBF共混膜的热学性能、力学性能和流变性能进行研究。广角X射线衍射以及差示扫描热量分析结果表明，PBF的加入提高了PLLA薄膜的结晶度，PLLA/PBF12共混薄膜的结晶度最高可达到35.1%。拉伸实验表明，PBF的加入改善了PLLA薄膜的延展性，PLLA/PBF6共混薄膜断裂伸长率最高可达到159.3%,是PLLA薄膜的50倍以上。动态流变测试表明，PLLA、PLLA/PBF3、PLLA/PBF6共混物在熔融状态下均为假塑性流体，PLLA/PBF12、PLLA/PBF24共混物在低频区为假塑性流体，在高频区为牛顿流体。当PBF的质量比分布为3%和6%时，PLLA的熔体黏度显著降低，加工流动性显著提升。     

聚乳酸/聚乙二醇共混物的热氧稳定性研究

热氧稳定性是材料加工、应用的重要参数。采用差热、热重分析研究聚乳酸/聚乙二醇共混物的热氧稳定性。混合比例相同,PEG相对分子质量对共混物热氧稳定性能的影响趋势不同;PLLA/PEG共混物的共混比例不同时,热氧稳定性降低幅度与共混物中PLLA百分数不成比例;PLLA/PEG共混物的热失重曲线中出现的转折表明共混物降解过程中PLLA链与PEG链可能发生了化学反应。     

复合型多金属氧酸盐的合成与应用

多金属氧酸盐(Polyoxometalates, POMs)是由高价态的过渡金属离子通过氧连接而成的一类多金属氧簇化合物，因其丰富的元素组成、可调控的多样结构及氧化还原活性，在催化、材料和医药等领域拥有广泛的应用。POMs在极性溶剂中通常有良好的溶解度，这导致其不易从反应体系分离。制备复合型POMs,一方面可以提高POMs的比表面积和稳定性，进而提高催化活性；另一方面可以降低POMs在极性溶剂中的溶解度，有利于回收及重复利用。主要综述了近年来复合型POMs的合成、性质及应用的研究现状。     

功能配位聚合物的研究热点

金属配位聚合物是一种新型功能性分子材料,近年来得到科学家的普遍关注。主要对配位聚合物在金属一氧簇化合物、三维开放式网络、缠结网络的研究热点进行了综述,综述了金属配位聚合物研究的重要性和国内外金属配位聚合物的研究工作。首先,对金属一氧簇化合物的各个类型分别进行介绍;其次,叙说了j维开放式网络的刚性多孔网络和柔性多孔网络：最后,介绍了缠结网络中的互穿网络和自穿网络;并对其发展前景作出了展望。     

可反应性纳米二氧化硅对聚乳酸结晶行为的影响

通过熔融共混法制备了聚乳酸（PLLA）／可反应性纳米二氧化硅（RNS）复合材料,用透射电子显微镜观察RNS在PLLA基体中的分散情况,用差示扫描量热仪（DSC）和X射线衍射仪（XRD）对复合材料的非等温结晶行为进行了研究,并利用Jeziomy法和Mo法对复合材料的非等温结晶动力学进行分析。结果表明,RNS在PLLA中分散均匀,RNS的加入虽不会改变PLLA的晶型,但RNS与PLLA之间的相互作用及其异相成核能力会对聚乳酸基体的结晶速率和结晶度产生影响,导致材料结晶过程发生变化。     

Transcrystalline structures of poly(l-lactide)

Poly(l-lactide) (PLLA) film containing transcrystalline (TC) structures can easily be obtained by placing PLLA films melted between two poly(tetrafluoroethylene) (PTFE) sheets, followed by isothermal crystallization at 122 °C. The fine structures of the PLLA-TC film were studied by various structural techniques such as X-ray diffractometry, optical microscopy and transmission electron microscopy. We also examined the purification effect upon the morphology of PLLA-TC film. The formation of the TC structures revealed that one-dimensional spherulitic growth occurred from the assembling impurities as nucleation agent near the PTFE substrate in the heterogeneous nucleation system. We found that the b-axis of PLLA crystal was parallel to the lamellae growth direction confirmed using X-ray diffraction. The precipitated PLLA film crystallized in a similar process exhibited scanty TC textures, suggesting that the existence of impurity in the PLLA sample was an important factor for the formation of those structures.     

Thermal properties and degradation characteristics of polylactide,linear low density polyethylene,and their blends

Melt blending of linear low density polyethylene (LLDPE) and polylactide (PLLA) was performed in an extrusion mixer with post extrusion blown film attachment with and without compatibilizer-grafted low density polyethylene maleic anhydride. The blend compositions were optimized for tensile properties as per ASTM D 882-91. Based on this, LLDPE 80 (80 wt% LLDPE & 20 wt% PLLA) and M-g-L 80/4 (80 wt% LLDPE, 20 wt% PLLA and 4 parts compatibilizer per hundred parts of resin) were found to be an optimum composition. FTIR reveals that the presence of compatibilizer shifts carbonyl peak hence some increase in interaction between LLDPE and PLLA. Morphological characteristics of the fracture surface of with and without compatibilizer blends were examined by scanning electron microscopy. It shows that use of compatibilizer enhances the dispersions of PLLA in LLDPE matrix. Thermogravimetric (TG) analysis of blends shows the M-g-L 80/4 blend has higher thermal stability among studied blends. The degradation study under different pH of soil compost gives that in alkaline condition and the presence of compatibilizer was favorable for degradation. This blend may be used for packaging application.     

Investigation of wicking phenomenon and tensile properties in three-layer composite nanofibrous PA/PLLA yarn

One critical property of a nanofibrous structure is the wicking behavior in contact with liquids. This work's purpose is fabrication and investigation of tensile and wicking properties of a newly designed three-layer nanofibrous yarn consisting of polyamide 6/poly(L-lactic acid) (PA/PLLA) with a similar idea to Bobtex spun yarn structure in which adhesion between core (PA) and sheath (PLLA) is provided with a thin layer of polymeric thin film. The tensile strength and strain decreased 32 and 46%, respectively, in a three-layer yarn compared with two-layer, that is, yarn without the adhesion film. In addition, the ultimate strength of the three-layer yarn was higher than a PLLA yarn. The vertical wicking test for three-layer nanofibrous yarn reveals that at short times, capillary rise kinetics follow the Lucas–Washburn law while increasing the take-up velocity of the take-up roller in yarn fabrication leads to increasing the maximum height of water in yarn.     

Confined crystallization morphology of poly(ϵ‐caprolactone) block within poly(ϵ‐caprolactone)–poly(l‐lactide) copolymers

The confined crystallization of poly(?‐caprolactone) (PCL) block in poly(?‐caprolactone)–poly(l ‐lactide) (PCL‐PLLA) copolymers was investigated using differential scanning calorimetry, polarized optical microscopy, scanning electronic microscopy and atomic force microscopy. To study the effect of crystallization and molecular chain motion state of PLLA blocks in PCL‐PLLA copolymers on PCL crystallization morphology, high‐temperature annealing (180 °C) and low‐temperature annealing (80 °C) were applied to treat the samples. It was found that the crystallization morphology of PCL block in PCL‐PLLA copolymers is not only related to the ratio of block components, but also related to the thermal history. After annealing PCL‐PLLA copolymers at 180 °C, the molten PCL blocks are rejected from the front of PLLA crystal growth into the amorphous regions, which will lead to PCL and PLLA blocks exhibiting obvious fractionated crystallization and forming various morphologies depending on the length of PLLA segment. On the contrary, PCL blocks more easily form banded spherulites after PCL‐PLLA copolymers are annealed at 80 °C because the preexisting PLLA crystal template and the dangling amorphous PLLA chains on PCL segments more easily cause unequal stresses at opposite fold surfaces of PCL lamellae during the growth process. Also, it was found that the growth rate of banded spherulites is less than that of classical spherulites and the growth rate of banded spherulites decreases with decreasing band spacing. © 2019 Society of Chemical Industry     

Synthesis of a poly(methyl methacrylate)/silica nano-composite by soaking of a microphase separated polymer film into a perhydropolysilazane solution

A novel synthetic method of poly(methyl methacrylate) (PMMA)/silica nano-composite with well-segregated PMMA and silica domains was proposed. To obtain the nano-composite, a poly(methyl methacrylate)-block-poly(2-hydroxyethyl methacrylate) (PMMA-block-PHEMA) film with PMMA and PHEMA domains was soaked into a pyridine/m-xylene/perhydropolysilazane (PHPS) mixture and calcinated at 90 °C under steam. PHPS was homogeneously introduced into the film and selectively converted to silica in PHEMA microdomains of the PMMA-block-PHEMA film. The morphology of the nano-composite was investigated by transmission election microscopy (TEM).     

Wetting behavior of electrospun poly(L‐lactic acid)/poly(vinyl alcohol) composite nonwovens

Poly(L ‐lactic acid) (PLLA) fibers have been extensively studied for various applications. In this work, PLLA and poly(vinyl alcohol) (PVA) were prepared by coelectrospinning to form composite nonwoven materials. The structures and diameter distribution of the electrospun PLLA/PVA composite nonwovens were examined by atomic force microscopy (AFM) and scanning electronic microscope (SEM). The wetting behavior of the electrospun PLLA/PVA composite nonwovens was also investigated using static contact angles and dynamic water adsorption measurements. It was observed that the addition of PVA in the electrospun PLLA/PVA composite nonwovens significantly alerted the contact angles and water adsorption of the composite materials. It was also found that the increase in the content of PLLA led to the increase in the surface contact angle and decrease in water adsorption of the electrospun PLLA/PVA nonwoven materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Formation of conductive polyaniline nanoarrays from block copolymer template via electroplating

Nanostructured thin films have drawn extensive attention because of their unique properties resulting from nanoscale features. One of the convenient ways to generate nanostructured thin films is to use pattern with nanoscale texture as a template for the reactions carrying out within the template. In this study, nanoporous thin film template was obtained from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA) with PLLA cylinder nanostructure, at which the PLLA block can be hydrolyzed to form the nanopatterns with cylinder nanopores on conductive substrate (i.e., ITO substrate). The nanoporous PS thin film template was stabilized by modification of substrate using hydroxyl terminated PS so as to enhance the adhesion with substrate for following electroplating process. Combining a pulse electroplating method with the control of micro current, polyanilines can be successfully synthesized within the template to fabricate well-defined of conductive polymer nanoarrays.     

Thermally induced crystallization and enzymatic degradation studies of poly (L‐lactic acid) films

Poly(L ‐lactic acid) (PLLA) films with different crystallinities were prepared by solvent casting and subsequently annealed at various temperatures (T_a) (80–110°C). The effects of crystallinity on enzymatic degradation of PLLA films were examined in the presence of proteinase K at 37°C by means of weight loss, DSC, FTIR spectroscopy, and optical microscopy. DSC and the absorbance ratio of 921 and 956 cm^?1 (A₉₂₁/A₉₅₆) were used to evaluate crystallinity changes during thermally induced crystallization and enzymatic hydrolysis. The highest percentage of weight loss was observed for the film with the lowest initial crystallinity and the lowest percentage of weight loss was observed for the film with highest crystallinity. FTIR investigation of degraded films showed a band at 922 cm^?1 and no band at 908 cm^?1 suggested that all degraded samples form α crystals. The rate of degradation was found to depend on the initial crystallinity of PLLA film and shown that enzymatic degradation kinetics followed first‐order kinetics for a given enzyme concentration. DSC crystallinity and IR absorbance ratio, A₉₂₁/A₉₅₆ ratio, showed no significant changes with degradation time for annealed PLLA films whereas as‐cast PLLA film showed an increase in crystallinity with degradation; this revealed that degradation takes place predominantly in the free amorphous region of annealed PLLA films without changing long range and short range order © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cold‐crystallization behavior of poly(L‐lactide)/ACR blend films investigated by in situ FTIR spectroscopy

The cold crystallization behavior of poly (L ‐lactide) (PLLA) blend films modified by small amount of acrylic rubber particles (ACR) have been investigated by in situ Fourier‐transform infrared (FTIR) spectroscopy. During the isothermal cold crystallization, the crystallization rate of PLLA is greatly improved with addition of only 1 wt % ACR. However, for PLLA with 8 wt % ACR, the crystallization rate is slower than that of neat PLLA. The relative crystallinity of PLLA with the addition of 1–5 wt % ACR is obviously higher than that of the neat PLLA. For the PLLA blend film with 3 % ACR, the relative crystallinity reaches a maximum. It was found that the addition of ACR particles below 5% accelerated the cold crystallization nucleation process and made the cold‐crystallization rate of PLLA/ACR be quicker than that of neat PLLA. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Suppression of Ni agglomeration in PLD fabricated Ni-YSZ composite for surface modification of SOFC anode

The suppression of Ni agglomeration in Ni-yttria stabilized zirconia (Ni-YSZ) nano-composite thin films deposited by pulsed laser deposition (PLD) has been investigated by varying post-annealing temperatures at a range of 800–1200 °C. Grain growth to a certain extent appears to be necessary to obtain a stable Ni-YSZ composite microstructure by suppressing massive Ni agglomeration. The microstructurally stable and uniform nano-porous Ni-YSZ thin film was obtained by 1200 °C post-annealing and reduction of the NiO–YSZ thin film, and it was applied as the surface modification layer of the bulk anode support used in conventional solid oxide fuel cells (SOFCs). By this approach, we were able to successfully realize a thin film electrolyte SOFC exhibiting the open cell voltage (OCV) higher than 1 V with a 1-μm thick film electrolyte on the porous anode support.