Amylose and Amylopectin Hybrid Materials via Enzymatic Pathways

Summary: Oligo- and polysaccharides are important macromolecules in living systems, showing their multifunctional characteristics in the construction of cell walls, energy storage, cell recognition and their immune response. Saccharides as organic raw materials can open new perspectives on the way to new biocompatible and biodegradable products which could help to overcome the problems resulting from the upcoming restrictions of petrochemical resources. Construction of well-defined carbohydrate polymer backbones is very challenging as it is difficult to realize complete regio and stereo-control of the glycosylating process. Most synthetic approaches are therefore based on the modification or degradation of naturally occurring polysaccharides resulting in less then perfect products. Enzymes have several remarkable catalytic properties compared with other types of catalysts in terms of their selectivity, high catalytic activity, lack of undesirable side reactions and operation under mild conditions. A biocatalytic pathway to synthesize saccharides is therefore very attractive as it results in well-defined polysaccharides avoiding the above drawbacks. When biogenic polysaccharides are combined with synthetic macromolecules, surfaces etc. materials with new interesting properties arise and the processability of the designed hybrid materials is facilitated. Amylose and amylopectin hybrid materials can be synthesized via enzymatic polymerization routes utilizing transferases. This approach opens access to well-defined hybrid structures bearing amylase or amylopectin moieties that cannot be synthesized by any other means.     

Modern mass spectrometry in the characterization and degradation of biodegradable polymers

In the last decades, the solid-waste management related to the extensively growing production of plastic materials, in concert with their durability, have stimulated increasing interest in biodegradable polymers. At present, a variety of biodegradable polymers has already been introduced onto the market and can now be competitive with non biodegradable thermoplastics in different fields (packaging, biomedical, textile, etc.). However, a significant economical effort is still directed in tailoring structural properties in order to further broaden the range of applications without impairing biodegradation. Improving the performance of biodegradable materials requires a good characterization of both physico-chemical and mechanical parameters. Polymer analysis can involve many different features including detailed characterization of chemical structures and compositions as well as average molecular mass determination. It is of outstanding importance in troubleshooting of a polymer manufacturing process and for quality control, especially in biomedical applications. This review describes recent trends in the structural characterization of biodegradable materials by modern mass spectrometry (MS). It provides an overview of the analytical tools used to evaluate their degradation. Several successful applications of MALDI-TOF MS (matrix assisted laser desorption ionization time of flight) and ESI MS (electrospray mass spectrometry) for the determination of the structural architecture of biodegradable macromolecules, including their topology, composition, chemical structure of the end groups have been reported. However, MS methodologies have been recently applied to evaluate the biodegradation of polymeric materials. ESI MS represents the most useful technique for characterizing water-soluble polymers possessing different end group structures, with the advantage of being easily interfaced with solution-based separation techniques such as high-performance liquid chromatography (HPLC).     

淀粉基高分子材料的研究进展

概述了近5年国内外在淀粉的化学、物理改性及其作为一种材料使用方面取得的最新研究进展.淀粉的化学改性主要介绍了淀粉的酯化、醚化、氧化、交联、接枝共聚等,而物理改性主要介绍了淀粉分别与黏土、脂肪族聚酯、聚乙烯醇以及纤维素等天然大分子的共混改性,同时还介绍了通过酸化制备淀粉纳米晶.淀粉基材料除了用于制备可生物降解塑料、吸附材...     

Properties of Starch Blends with Biodegradable Polymers

Abstract

Starch, one of the most inexpensive and most readily available of all natural polymers, can be processed into thermoplastic materials only in the presence of plasticizers and under the action of heat and shear. Poor water resistance and low strength are limiting factors for the use of materials manufactured only from starch, and hence the modification of starch is often achieved by blending aliphatic polyesters. In this review, the literatures concerning the properties of various blends of starch and aliphatic polyesters have been summarized. The biodegradable rates of blends can be controlled to a certain extent depending on the constitutions of blends, and the mechanical properties of blends are close to those of traditional plastics such as polyethylene and polystyrene. The reduction of their sensitivity to humidity makes these materials suitable for the production of biodegradable films, injection-molded items, and foams.     

Dendritic macromers for hydrogel formation: Tailored materials for ophthalmic,orthopedic, and biotech applications

Dendritic macromolecules are well‐defined highly branched macromolecules synthesized via a divergent or convergent approach. A salient feature of the macromolecules described herein, and a goal of our research effort, is to prepare dendritic macromolecules suitable for in vitro and in vivo use by focusing on biocompatible building blocks and biodegradable linkages. These dendritic macromolecules can be subsequently crosslinked to form hydrogels using a photochemical acrylate‐based or a chemical ligation strategy. The properties—mechanical, swelling, degradation, and so forth—of the hydrogels can be tuned by altering the composition, crosslinking chemistry, wt %, generation number and so forth. The utility and diverse applicability is demonstrated through successful use of these hydrogels in three unique applications: hydrogel adhesives for repairing corneal wounds, hydrogel scaffolds for cartilage tissue engineering, and hydrogel reaction chambers for high throughput screening of molecular recognition events. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 383–400, 2008.     

Polyolefins with controlled environmental degradability

Antioxidants and stabilisers, developed to increase the durability of polyolefins, in combination with prooxidant transition metal complexes provide industrial products with widely variable but controlled lifetimes. The low molar mass oxidation products formed during photo-oxidation and thermal oxidation are biodegradable and oxo-biodegradable polyolefins are now widely used in agricultural applications and in degradable packaging as examples. The scientific basis for the performance of oxo-biodegradable materials is explained with reference to naturally occurring macromolecules. Comparison with hydro-biodegradable materials is made and the need is demonstrated for performance standards to be developed that mimic nature's resource recovery mechanism, that of oxo-biodegradation.     

Nanoparticles from Chitosan

Novel biodegradable nanoparticles were synthesized by chemical modification of the chitosan linear chain. A natural dicarboxylic acid (malic acid) was used as a crosslinking agent for intramolecular covalent condensation reaction to obtain hydrophilic nanoparticles based on chitosan. A variety of methods including, solubility studies, laser light scattering (DLS), transmission electron microscopy (TEM) and nuclear magnetic resonance (NMR) was used to characterize the crosslinked macromolecules. The prepared biodegradable chitosan nanoparticles, soluble in aqueous media, might be useful for various biomedical applications, like injectable drug- or gene-delivery systems.     

Polymers Containing Lactone Groups

Polymers containing intact lactone groups are a new class of macromolecules with reactive groups, which are relatively easy to obtain by polymerization, polycondensation and polyaddition, as well as by reactions on existing macromolecules. Polymers with β-lactone Groups in particular can enter into numerous addition reactions, which can be used, for example, to obtain macromolecules containing hydroxy acid or amino acid groupings. The reactions proceed under mild conditions, and can even be carried out in aqueous media, frequently giving water-soluble polymers. The polymers can be cross-linked at low temperatures, even from the aqueous phase, by the addition of bifunctional or oligofunctional reagents. Polymers containing β-lactone groups can also be used as a basis for graft co-polymers; polyester or polyether branches can be grafted on, depending on whether monomeric lactones or monomeric epoxides are used.     

有关“环境友好塑料”几个概念的澄清

生物塑料、生物降解塑料、生物基塑料统称为环境友好塑料,但它们三者的侧重点各有不同,既有区别,也有联系,本文对以上三个概念的意义做了详细的解释和澄清。生物塑料注重于生产原料的生物来源性和制造过程的生物技术性;生物降解塑料则注重于它是否可以被生物降解,其原料可以来自于可再生资源,也可来自于石油资源;生物基塑料则关注其生产原料是否来自于可再生资源,而对其是否可以生物降解没有特别要求。     

生物降解聚合物的研究和产业化进展及展望

结合作者等近十年来在生物降解聚合物领域的研究和产业化工作,本文概述了聚乳酸、聚氨基酸、聚对二氧六环酮及其它生物降解聚合物的合成进展,综述了可生物降解温度敏感水凝胶、形状记忆高分子材料的研究概况,阐述了可生物降解聚合物在生物活性大分子控释体系、超细纤维组织工程支架上的应用研究,介绍了可生物降解聚合物在食品包装、纺织和汽车电子等方面的应用,总结了可生物降解聚合物、医疗器械、药物制剂和组织工程等领域产业化近况.最后展望了生物降解聚合物的研究、应用和产业化前景.     

Biodegradable Multiphase Systems Based on Plasticized Starch: A Review

Abstract

The aim of this review is to show the relationships between the structure, the process, and the properties of biodegradable multiphase systems based on plasticized starch (PLS), the so‐called “thermoplastic starch.” These mutiphase materials are obtained when associating association between plasticized starches and other biodegradable materials, such as biodegradable polyesters [polycaprolactone (PCL), polyhydroxyalkanoates (PHAs), polylactic acid (PLA), polyesteramide (PEA), aliphatic, and aromatic copolyesters], or agro‐materials (ligno‐cellulosic fiber, lignin etc.). Depending on materials (soft, rigid) and the plastic processing system used, various structures (blends, composites, multilayers) can be obtained. The compatibility problematic between these hetero‐materials is analyzed. These starchy products show some interesting properties and have some applications in different fields: packaging, sports, catering, agriculture and gardening, or hygiene.     

Matrix polymerization of aniline in the presence of polyamides containing sulfo acid groups

The matrix synthesis of polyaniline in the presence of water-soluble aromatic polyamides containing sulfo acid groups has been studied. It has been shown that the nature of polyacid and the concentration of reagents affect the shape and dynamics of a change in absorption spectra. The S-shaped profile of kinetic curves for spectra variation and the experiments on the seed polymerization provide evidence for the autocatalytic character of polymerization. It has been concluded that, depending on the nature of polyacid, polymer complexes form in which polyaniline macromolecules are situated along main chains of polyacid macromolecules (the two-stream structure) or appear as side chains of polyacid macromolecules (the comb-shape structure). In the latter case, polyaniline macromolecules serve as ionic bridges crosslinking polyacid macromolecules, as is confirmed by the viscometric study of solutions in the course of polymerization.     

Efficient route to well‐characterized homo,block, and statistical polymers containing terpyridine in the side chain

The incorporation of metal–ligand interactions into macromolecules imparts to them unique and potentially useful properties. We report the synthesis of homo, block, and statistical copolymers with controlled molecular weights, compositions, and relatively narrow polydispersities via atom transfer radical polymerization that contain activated esters for the subsequent incorporation of terpyridine. This approach is universal and allows facile access to macromolecules with rich chemical functions, illustrated here with metal ligands. Comonomers include methyl, n‐butyl, and poly(ethylene glycol) methyl ether methacrylate as well as styrene. The addition of lanthanide ions to the final copolymers generates emissive materials with blue, green, red, or purple light, depending on the metal used. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5831–5843, 2005     

Mechanical properties decay and morphological behaviour of biodegradable films for agricultural mulching in real scale experiment

The use of plastic materials in agriculture causes the serious drawback of huge quantities of waste. The introduction of biodegradable materials, which can be disposed directly into the soil, can be one possible solution to this problem. Biodegradable materials are actually innovative materials; therefore, their physical properties must be evaluated in relation to their functionality during the use in field. In the present research results of experimental tests carried out on biodegradable films used in strawberries protected cultivation are presented. The decay of some relevant physical parameters of biodegradable films during the cultivation period was monitored by laboratory tests (SEM analysis, mechanical tensile tests and infrared reflectance spectroscopy). Infrared spectroscopy clearly indicated that the mechanical degradation starts from the starch component of the material. Tensile tests showed that the value of elongation at break of biodegradable materials decreased in some cases by 300% after 10 days of field application.     

Measuring the size of polymers with negative radii using MALS/QELS: an exploration of the thermodynamic radius

The concept of 'size' in polymer science can have several interpretations, including definitions that rely on either statistical or equivalent-hard-sphere measures of the spatial extent of macromolecules in solution. A definition such as that of the equivalent thermodynamic radius (R(T)), which relies on the second virial coefficient of the polymer solution, offers the possibility of a zero or even a negative size parameter for macromolecules, depending on whether the polymer solution is in a theta or poor thermodynamic state, respectively. Here, we present the results of multi-angle light scattering measurements of R(T) for polystyrene and poly(methyl methacrylate), showing positive, negative, and zero values for this radius, depending on dilute solution thermodynamics. These results are augmented with measurements of the hydrodynamic radius, using quasi-elastic light scattering, and with random-walk-based calculations of the root-mean-square and viscometric radii. Re-examination of the literature provides additional examples of negative radii of polymers and oligomers.     

Biodegradable elastomer for soft tissue engineering

In this work we present the synthesis of a biodegradable, elastomeric material with a wide range of mechanical properties. The synthesis of the material was done by condensation polymerization of malic acid and 1,12–dodecandiol. The synthesized materials have low Young’s modulus ranging from about 1 to 4 MPa and a high elongation at break of 25–737% depending on the crosslinking density of the system. The cell growth observed under microscope showed good proliferation at 3 days of culture indicating good biocompatibility and support of L929 cells growth. The fabrication of 3D scaffold from these materials using the super critical CO₂ foaming method was also attempted. This method of scaffold fabrication is appropriate for materials that are easily hydrolysable and it also has the advantage of being a solvent free process. These materials are generally soft, biocompatible and biodegradable making them suitable for tissue engineering of soft tissues that are elastic in nature like muscles and blood vessels.     

Aqueous Self‐Assembly of Purely Hydrophilic Block Copolymers into Giant Vesicles

Self‐assembly of macromolecules is fundamental to life itself, and historically, these systems have been primitively mimicked by the development of amphiphilic systems, driven by the hydrophobic effect. Herein, we demonstrate that self‐assembly of purely hydrophilic systems can be readily achieved with similar ease and success. We have synthesized double hydrophilic block copolymers from polysaccharides and poly(ethylene oxide) or poly(sarcosine) to yield high molar mass diblock copolymers through oxime chemistry. These hydrophilic materials can easily assemble into nanosized (<500 nm) and microsized (>5 μm) polymeric vesicles depending on concentration and diblock composition. Because of the solely hydrophilic nature of these materials, we expect them to be extraordinarily water permeable systems that would be well suited for use as cellular mimics.     

IR-spectroscopic examination of polytetrafluoroethylene and its modified forms

The results of IR-spectroscopic examinations of the molecular and supramolecular structure of polytetrafluoroethylene and polymer materials thereof were summarized. It was shown that, upon heat, mechanical, and other treatment, as well as under radiation exposure, polytetrafluoroethylene preserves its chain-helical conformation, and the resulting modified forms consist of crystalline and amorphous phases in a ratio depending on the history of the sample. The degree of the structural ordering in the polymer decreases with increasing temperature and pressure. The formation of branched moieties and short macromolecules with double bonds (?CF=CF₂) in the terminal groups is specific for the process caused by thermal and radiation-induced degradation. The oxidation of the polymer macromolecules requires applying high irradiation doses and heating samples in an oxygen or air atmosphere.     

Synthesis of poly(ester amide)s with lateral groups from a bulk polycondensation reaction with formation of sodium chloride salts

Poly(ester amide)s with a regular sequence and derived from diamine, dicarboxylic acid, and glycolic acid units can be easily synthesized by using a thermal polycondensation method based on the formation of metal halide salts as a driving force. These new poly(ester amide)s have tuneable properties depending on the number of methylene groups and constitute a group of materials with potential interest as biodegradable materials in applications such as surgical sutures. The present work reveals that the proposed synthesis can also be applied when esters of L ‐lysine are used as a diamine unit since no secondary reactions such as transesterification occur under the required polymerization conditions. The possibility of linking compounds with pharmacological activity to the carboxylic acid groups of lysine extends the interest of the referred materials, for example, as drug delivery systems. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 661–667, 2008     

To compost or not to compost: Carbon and energy footprints of biodegradable materials’ waste treatment

Many life cycle assessments of bio-based and biodegradable materials neglect the post-consumer waste treatment phase because of a lack of consistent data, even though this stage of the life cycle may strongly influence the conclusions. The aim of this paper is to approximate carbon and energy footprints of the waste treatment phase and to find out what the best waste treatment option for biodegradable materials is by modelling home and industrial composting, anaerobic digestion and incineration. We have compiled data-sets for the following biodegradable materials: paper, cellulose, starch, polylactic acid (PLA), starch/polycaprolactone (MaterBi), polybutyrate-adipate-terephthalate (PBAT, Ecoflex) and polyhydroxyalkanoates (PHA) on the basis of an extensive literature search, experiments and analogies with materials for which significant experience has been made. During biological waste treatment, the materials are metabolised so a part of their embodied carbon is emitted into air and the remainder is stored as compost or digestate. The compost or digestate can replace soil conditioners supporting humus formation, which is a benefit that cannot be achieved artificially. Experimental data on biodegradable materials shows a range across the amount of carbon stored of these materials, and more trials will be required in the future to reduce these uncertainties. Experimental data has also shown that home and industrial composting differ in their emissions of nitrous oxide and methane, but it should be noted that data availability on home composting is limited. The results show that anaerobic digestion has the lowest footprint for the current level of technology, but incineration may become better in the future if energy efficiency in waste incineration plants improves significantly. Home composting is roughly equal to incineration with energy recovery in terms of carbon and energy footprint when carbon credits are considered. The same applies to industrial composting if carbon credits are assigned for compost to replace straw. Carbon credits can therefore considerably affect the results, but there are significant uncertainties in how they are calculated. Incineration may become better than home composting in the future if the average energy efficiency in waste incineration plants improves significantly. However, biological waste treatment options should be chosen when soil carbon is a limiting factor.