聚己内酯接枝淀粉纳米晶的制备

通过异氰酸酯与端羟基聚己内酯反应制备端异氰酸酯基预聚体,再接枝到淀粉纳米晶表面,制备了端基分子量可控的聚己内酯接枝淀粉纳米晶。分别用FTIR和1H NMR对所制备的聚己内酯接枝淀粉纳米晶进行表征,结果表明,有少量聚己内酯接枝到淀粉纳米晶表面。XRD结果表明,接枝了少量聚己内酯后的淀粉纳米晶的晶型和结晶度与未接枝的淀粉纳米晶基本一致。聚己内酯接枝淀粉纳米晶的熔融温度由115℃左右提高到122℃左右,并且温度范围变宽。浸润性实验表明,聚己内酯接枝淀粉纳米晶与水不浸润,其表面已具有疏水性。聚己内酯仅接枝在淀粉纳米晶的表面,改善了淀粉纳米晶表面的疏水性能和与聚酯类聚合物的界面相容性。聚己内酯接枝淀粉纳米晶有望用于可降解聚酯类高分子材料,如聚乳酸(PLA)、聚己内酯(PCL)、聚丁二酸丁二醇酯(PBS)等,改善其力学性能和生物降解性能等。     

热塑性淀粉耐水性的化学与物理作用机制

石油资源的短缺以及减轻石油基聚合物所产生的环境负担的必要性,推动了生物可降解材料的开发和生产。近几十年来天然聚合物由于无毒性、可生物降解性和生物相容性正在某些领域取代目前的合成聚合物。淀粉由于其可再生性、可生物降解性、低成本和易获得性已经被广泛研究用于制造可生物降解的复合材料,应用于农业、食品、医药和包装行业。但淀粉的多羟基结构赋予其很强的亲水性,这种湿度敏感性限制了它们的机械性能并影响到其应用。本文主要从提高热塑性淀粉耐水性的物理与化学作用机理的角度出发,总结和归纳了近年来国内外以提高热塑性淀粉材料的耐水性能和降低其对环境湿度敏感性为目的的研究工作,介绍了影响耐水性能的相关因素以及改善方法,并指出今后研究工作的发展方向。     

具有超疏水表面的硅/二氧化硅层次结构薄膜

目前报道的硅基材料的超疏水表面主要是通过制备粗糙微观结构,并在其表面修饰表面能相对较低的有机物两个步骤来实现的,在户外等实际环境中应用时存在由于表面修饰有机物的降解而逐渐失去超疏水性的问题.本工作以液态金属锡作为生长衬底,通过化学气相沉积(CVD)法制备了一种具有超疏水性能的硅基薄膜结构.利用扫描电镜(SEM),透射电镜(TEM)以及X射线衍射(XRD)等手段对产物的表面形貌和组成结构进行分析发现,薄膜表面由竖直生长的硅/二氧化硅(Si/SiO2)核壳层次结构组成.采用Cassie理论模型对其超疏水性能的产生提出了可能的解释.发现构成薄膜表面的Si/SiO2层次结构单元的形貌是影响超疏水性能的重要因素.相对于以前报道的硅基材料的超疏水表面,这种新结构的超疏水性能不依赖于表面化学修饰,有望拓宽硅基材料的应用环境.     

官能团化聚己内酯的制备及其生物应用

聚己内酯(PCL)是一种疏水的、半结晶的、可降解的脂肪族聚合物,其具有良好的生物相容性、药物透过性和机械性能,在药物缓释和组织工程领域得到了广泛的关注。由于其结晶性强,亲水性差,生物降解速度慢,限制了其在生物医用领域更广泛的应用。聚己内酯的官能团化可实现对聚酯材料亲疏水性、降解速率等物化性质的调节,同时,活性官能团的引入便于对PCL的进一步化学修饰,有利于拓宽聚己内酯类材料的生物医用领域。本文详细介绍在聚己内酯骨架引入侧基官能团的化学方法,并简要阐述了官能团化聚己内酯在生物医用材料领域的应用。     

完全降解聚乳酸共混复合材料的研究进展

聚乳酸(PLA)是可完全生物降解的材料,广泛应用于包装、纺织、生物医用等领域。但其具有性脆,价格较高,疏水性大等缺点,限制了应用发展。近年来对聚乳酸共混改性已成为研究热点。根据共混组分的生物降解性,聚乳酸共混体系分为完全生物降解体系和部分生物降解体系。文中综述了近年来完全生物降解聚乳酸共混体系的研究,主要阐述了PLA/淀粉、PLA/天然纤维复合材料,并简要介绍了PLA/甲壳素、PLA/蛋白等PLA/天然高分子复合材料,以及PLA/PCL、PLA/PPC、PLA/PEO等PLA/合成高分子复合材料。     

新型官能团化聚己内酯的研究进展

聚己内酯(PCL)是一种具有良好药物透过性的可生物降解的脂肪族聚酯,是一类优良的药物载体.由于其结晶性强,亲水性差,生物降解速度慢,限制了其在组织工程等生物医用领域更广泛的临床应用.在PCL主链上引入功能性官能团既可有效地降低其结晶性、改善其亲水性、调控其降解速率,同时又可通过反应性官能团进行进一步的化学改性或生物活性化修饰,已成为生物可降解材料新的研究热点.本文综述了含侧基官能团己内酯单体的合成及其聚合反应,简要介绍了侧基官能团对聚己内酯性能的影响.     

酶催化合成羟乙基淀粉/ε-己内酯接枝共聚物

淀粉可降解,是一种环境友好型材料,在造纸工业、日用化工、纺织工业、石油工业、食品等[1～2]方面应用广泛.羟乙基淀粉(HES)是用含支链淀粉比较丰富的玉米淀粉和马铃薯淀粉与环氧乙烷在碱性条件下得到的一种产物.Ahmed Besheer等[3]报道对HES进行疏水改性,即在淀粉中引入疏水基团,打破了传统淀粉亲水的单一性质,有望可以作为可降解的生物相容性材料应用于生物医药领域、缓释领域[4～5].     

生物基高分子阻燃涂层的研究进展

生物基高分子由于具有绿色、环保、可再生和生物降解的特性,已经逐渐被应用到包装、汽车、电子电器等领域.部分生物基高分子(如壳聚糖、淀粉等)由于具有良好的成炭性而逐渐被应用于阻燃领域.这些生物基高分子主要通过添加和涂覆的方式被引入到材料中赋予材料良好的阻燃性能.本文综述了含有壳聚糖、淀粉、DNA以及植酸等生物基高分子材料阻燃涂层的研究进展,包括每种涂层的成分、涂覆方式、阻燃效果等,并简要介绍了几种生物基功能阻燃涂层.最后,对生物基阻燃涂层的发展趋势进行了展望.     

淀粉基生物可降解材料的研究新进展

从淀粉的微观结构、加工过程中的相变及淀粉改性等基础理论出发,针对淀粉基材料存在的机械性能较低,对水敏感性高等缺陷,以及发泡材料制备的特点,介绍了最新的基础研究和应用研究成果.本文从淀粉基全天然高分子复合材料、纳米复合材料、自增强复合材料及功能性复合材料四个方面介绍了通过共混与复合制备淀粉基可生物降解材料,并且介绍了淀粉基材料防水改性的相关进展.指出使用可再生的天然高分子材料对淀粉进行改性,不仅能够提高材料的各种性能,而且由于所有组分都来源于天然材料,制备出的共混、复合和涂层材料也都环保安全,甚至可以用来制备可食用包装,为研制新型淀粉基材料提供有力的理论和技术支持.另外,目前对水在淀粉基发泡材料中如何同时担任增塑剂和发泡剂的机理研究取得突破性进展,发现并控制了泡孔结构由闭孔到开孔的转换临界点,研制并产业化了全淀粉发泡材料.基于上述讨论,指出淀粉基可生物降解材料既有机遇,同时也面临挑战.     

在不同溶剂中制备生物质基超疏水材料的研究进展

超疏水材料因具有超高的拒水性以及自清洁能力而备受关注,但是在制备过程中也因所选用溶剂和低表面能物质不同给环境带来不同程度的压力。生物质材料可再生、价格低并且绿色无污染,常用于超疏水材料的制备。本文介绍了生物质基超疏水材料的制备方法,并按照制备技术中所用溶剂不同分类,将生物质基超疏水材料分为有机溶剂型、水基/半水基型、无溶剂型三类,同时分析了三种不同类型超疏水材料的优势以及劣势。最后,总结了制备环保型超疏水材料的方法,并且展望了生物质基超疏水材料未来的发展方向。     

Elaboration and Characterization of Starch/ Poly(caprolactone) Blends

A starch-based biodegradable material was prepared in two steps. Firstly, starch was chemically modified by using formic acid at 20°C to obtained degrees of substitution of about 1.2. The level of destructuration was also assessed using dynamic rheological measurements. Native starch or starch ester were then mixed with poly(caprolactone) and different polyester oligomers were added as compatibilisers and plasticizing agents. PCL oligomers were found to be the most efficient ones. A significant improvement of the elongation at break of starch formate/PCL/oligo PCL blends was achieved.     

Synthesis and characterization of compatibilized poly(ϵ‐caprolactone)/granular starch composites

To improve the mechanical properties of granular corn starch‐filled poly(ϵ‐caprolactone) (PCL) compositions, three strategies were investigated including the hydrophobic coating of starch granules by reaction with n‐butyl isocyanate, the addition of PCL‐grafted dextran (PGD) as an amphiphilic compatibilizer, and the use of PCL‐grafted granular starch (PGS). Except for the chemical modification of granular starch by reaction with n‐butyl isocyanate, the synthesis of both PGD and PGS relies upon the controlled ring‐opening polymerization (ROP) of ϵ‐caprolactone (CL) initiated by Al‐alkoxides generated onto the polysaccharide, either dextran or starch particles. While the hydrophobic coating of starch only provides higher tensile strength and elongation at break, these properties as well as Young's modulus and strength at yield of the PCL/starch blends were remarkably increased by locating the PCL‐grafted dextran at the filler/matrix interface. It is however worth pointing out that a tougher and stiffer material was obtained by melt blending PGS and pure PCL. These property changes were analyzed and clearly related to parameters such as filler dispersion, interfacial tension, interfacial adhesion and reinforcement by PCL crystallites.     

Influence of various starch types on PCL/starch blends anaerobic biodegradation

Research concentrated on the biodegradable capability of PCL blends with various types of starch in an anaerobic aqueous environment of mesophilic sludge from a municipal wastewater treatment plant. For blend preparation, use was made of a native starch Meritena from maize, another from Waxy – a genetically modified type of maize, as well as Gel Instant, a gelatinized starch, and an amaranth starch. Additional PCL/starch blends were prepared from the same starch types, but these were initially plasticized with glycerol. The biodegradability tests were supplemented with thermo gravimetric analysis (TGA), and differential scanning calorimetry (DSC); morphology was identified using scanning electron microscopy (SEM), plus mechanical properties were also tested. While mixtures of PCL with starches plasticized with glycerol exhibited improved mechanical properties and a higher degree of biodegradation in the anaerobic environment, mixtures of PCL with pure forms of starch were ascertained as rather resistant to the anaerobic aqueous environment. TGA and DSC analysis confirmed the removal of starch and glycerol from the PCL matrix. SEM then proved these results through the absence of starch grains in the samples following anaerobic biodegradation.     

Synthesis and characterization of starch-graft-polycaprolactone as compatibilizer for starch/polycarprolactone blends

Polycaprolactone (PCL) was grafted onto starch through introduction of urethane linkages. The grafting reaction was carried out in two steps. The first step was the reaction of hydroxyl-terminated PCL with 2,4-tolylene diisocyanate. The isocyanate terminated PCL was then reacted with starch to obtain starch-graft-polycaprolactone (starch-g-PCL). The grafting reaction was confirmed by FT-IR spectroscopy. The compatibility of the starch/PCL blend was enhanced with a compatibilizer, starch-g-PCL, whose amount was 3 wt.-% of the blend. The tensile strength and morphology of the compatibilized blend were determined. It was found that the compatibilized starch/PCL blend has finer phase domains and an improved interfacial adhesion. Mechanical properties of the compatibilized blend were found to be significantly higher than those of the corresponding uncompatibilized starch/PCL blend.     

Biodegradable compositions by reactive processing of aliphatic polyester/polysaccharide blends

Commercially available biodegradable aliphatic polyesters, i.e., high molecular weight poly(ϵ-caprolactone) (PCL) and polylactide (PLA), were melt blended with a well-known natural and biodegradable polysaccharide: starch either as corn starch granules or as thermoplastic corn starch after plasticization with glycerol. Conventional melt blending yielded compositions with poor mechanical performances as a result of lack of interfacial adhesion between the rather hydrophobic polyester matrix and the highly hydrophilic and moisture sensitive starch phase. Interface compatibilization was achieved via two different strategies depending on the nature of the polyester chains. In case of PLA/starch compositions, PLA chains were grafted with maleic anhydride through a free radical reaction conducted by reactive extrusion. The maleic anhydride-grafted PLA chains (MAG-PLA) allowed for reinforcing the interfacial adhesion with granular starch as attested by TEM of cryofracture surface. As far as PCL/starch blends were concerned, the compatibilization was achieved via the interfacial localization of amphiphilic graft copolymers formed by grafting of PCL chains onto a polysaccharide backbone such as dextran. The PCL-grafted polysaccharide copolymers were synthesized by controlled ring-opening polymerization of ϵ-caprolactone proceeding via a coordination-insertion mechanism. These compatibilized PCL/starch compositions displayed much improved mechanical properties as determined by tensile testing as well as a much more rapid biodegradation as measured by composting testing.     

Gamma Irradiation Effects on Mechanical and Thermal Properties and Biodegradation of Poly(3-hydroxybutyrate) Based Films

Summary: Their biodegradable properties make polyhydroxyalkanoates (PHAs) ideal candidates for innovative applications. Many studies have been primarily oriented to poly(3-hydroxybutyrate) (PHB) and poly(3-hydroxybutyrate-co-3-valerate) (PHBV) and afterwards to blends of PHAs with synthetic biodegradable polymers, such as poly(ε-caprolactone) (PCL). Medical and pharmaceutical devices require sterilization and γ irradiation could provide a proper alternative since it assures storage stability and microbiological safety. This contribution presents the effect of γ irradiation on the mechanical and thermal properties and on the biodegradation of PHB, PHBV and a commercial PHB/PCL blend. Samples, prepared by compression moulding, were irradiated in air at a constant dose rate of 10 kGy/h, from 10 to 179 kGy. Polymer chain scission was assessed by changes in the molecular weight, thermal properties and tensile behaviour. The correlation between absorbed dose and changes in the mechanical properties and biodegradation is discussed in detail. The optimum dose to guarantee microbiological sterilization without damage of the structure or meaningful loss of the mechanical properties is also reported.     

Structure–property relationship in PCL/starch blend compatibilized with starch‐g‐PCL copolymer

The polycaprolactone (PCL)/starch blends were prepared by using the starch‐g‐PCL (SGCL) graft copolymers as compatibilizers, and their mechanical properties were correlated with the compatibilizing effect of the SGCL copolymers having various molecular structures. The modulus and strength of the PCL/starch blend were decreased, whereas the percent elongation and the toughness were increased remarkably with the addition of SGCL having appropriate graft structure. These property changes were analyzed in terms of the PCL crystallinity and the interfacial adhesion between the PCL matrix and starch dispersion phases, which were dominated by the compatibilizing effects of the SGCL copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2430–2438, 1999     

Superhydrophobicity of PHBV fibrous surface with bead-on-string structure

A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibrous surface with various bead-on-string structures was fabricated by electrospinning. PHBV was electrospun at various concentrations and then CF4 plasma treatment was employed to further improve the hydrophobicity of the PHBV fiber surfaces. The surface morphology of the electrospun PHBV mats was observed by scanning electron microscopy (SEM). The surface properties were characterized by water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). The surface morphology of the electrospun PHBV fibrous mats with the bead-son-string structure varied with the solution concentration. The WCA of all of the electrospun PHBV mats was higher than that of the PHBV film. In particular, a very rough fiber surface including porous beads was observed when PHBV was electrospun from the solution with a concentration of 26 wt%. Also, its WCA further increased from 141 degrees to 158 degrees after CF(4) plasma treatment for 150 s. PHBV can be rendered superhydrophobic by controlling the surface morphology and surface energy, which can be achieved by adjusting the electrospinning and plasma treatment conditions.     

Synthesis of Starch-g-Poly(glycidyl methacrylate) and Its Blending with Poly(ϵ-caprolactone) and Nylon 610

Different amounts of glycidyl methacrylate (GMA) were grafted onto corn starch dispersed in water or dimethyl sulfoxide (DMSO) to yield starch-graft-poly(glycidyl methacrylate) (ST-g-PGMA). ST-g-PGMAW, obtained by grafting PGMA onto corn starch that was dispersed in water, showed a higher PGMA grafting content and a lower content of the homopolymerized PGMA than ST-g-PGMAD, which was prepared in DMSO. The modified starches were blended with poly(ϵ-caprolactone) (PCL) and nylon 610, respectively, and the tensile properties of the blends were measured by UTM. Mechanical properties of the biodegradable ST-g-PGMA/PCL blends were dependent on the PGMAD content grafted on starch. Without dramatic loss of the tensile properties of PCL, ST-g-PGMAW was melt blended with PCL. Meanwhile, an increase in the tensile modulus was observed in the ST-g-PGMAW/nylon 610 blend. When nylon 610 was reacted with ST-g-PGMAW in DMSO in the presence of triethylamine, the tensile modulus and strength were much higher than those of the pure nylon 610, and phase-separated domains of starch were not observed microscopically.     

Starch/Polycaprolactone Blends Compatibilized with Starch Modified Polyurethane

Starch modified polyurethane(St-PCL) was synthesized via chemical modification of corn starch with hexamethylene diisocyanate terminated polycaprolactone. The obtained St-PCL with different grafting rates was used as compatibilizer of starch/polycaprolactone(St/PCL) blend. The structure of St-PCL was confirmed by FTIR, and the grafting rate could reach as high as 64%. In addition, a lower St-PCL amount can effectively improve the compatibility of St/PCL blends. And the thermal, mechanical and hydrophobic properties of St/PCL blends could be tailored by the amount of St-PCL.