Enzymatic polymerization materials

In the pendent chain systems, the dmg is chemically bound to a polymer backbone and is released by hydrolytic or enzymatic cleavage of the chemical bond. The dmg may be attached directiy to the polymer or may be linked via a spacer group. The spacer group may be used to affect the rate of dmg release and the hydrophilicity of the system. These systems allow very high dmg loadings (over 80 wt %) (89) which decrease the cost of the polymeric materials used ia the systems. These systems have beea examiaed by many iavestigators (111,112). 

Production of all naturally occurring polymers in vivo is catalyzed by enzymes. Polymerizations catalyzed by an enzyme ( enzymatic polymerizations ) have received much attention as new methodology [6-11], since in recent years structural variation of synthetic targets on polymers has begun to develop highly selective polymerizations for the increasing demands in the production of various functional polymers in material science. So far, in vitro syntheses of not only biopolymers but also non-natural synthetic polymers through enzymatic catalysis have been achieved [6-11]. 

By means of genetic engineering, including cloning and site-directed mutagenesis, it has become possible for modern synthetic chemists to utilize a sufficient amount of isolated enzyme catalysts and to modify the reactivity, stability, or even specificity of enzymes. Therefore, polymerizations catalyzed by isolated enzyme are expected to create a new area of precision polymer syntheses. Furthermore, enzymatic polymerizations have great potential as an environmentally friendly synthetic process of polymeric materials. 

Synthesis of aminopolysaccharides, therefore, is one of the important research areas in the field of functional materials, examples of biorelated polymers, antibacterial substance, and biodegradable polymers as well as materials for drugs and matrices of drug delivery systems. Only a few methods, however, such as ring-opening polymerization and enzymatic polymerization have been available for the precision synthesis of aminopolysaccharides [4,5],... 

An interesting feature of this enzymatic polymerization in [BMIM]PF6 is that the polymeric material exhibited remarkably narrow polydispersity values, Mw/Mn = 1.04-1.03, a value that was maintained in the seven-day test. The authors related this value to the insolubility of the polymer formed in the ionic liquid after it exceeds a certain molecular weight limit. This observation opens the possibility of tailoring ionic liquids with varying solvating abilities for structural manipulation of desired polymeric material. 

Plants and animals synthesize a number of polymers (e.g., polysaccharides, proteins, nucleic acids) by reactions that almost always require a catalyst. The catalysts present in living systems are usually proteins and are called enzymes. Reactions catalyzed by enzymes are called enzymatic reactions, polymerizations catalyzed by enzymes are enzymatic polymerizations. Humans benefit from naturally occurring polymers in many ways. Our plant and animal foodstuffs consist of these polymers as well as nonpolymeric materials (e.g., sugar, vitamins, minerals). We use the polysaccharide cellulose (wood) to build homes and other structures and to produce paper. 

Crosslinking of polymers is usually applied to stabilize the macroscopic morphology or shape of a material. In most cases, it results in insoluble polymeric materials, e.g., for polymeric coatings. In the chemoenzymatic strategies towards polymer networks, the enzymatic step is exclusively applied to synthesize the... 

Various a-methylenemacrolides were enzymatically polymerized to polyesters having polymerizable methacrylic methylene groups in the main chain (Fig. 3, left). The free-radical polymerization of these materials produced crosslinked polymer gels [10, 12]. A different chemoenzymatic approach to crosslinked polymers was recently introduced by van der Meulen et al. for novel biomedical materials [11]. Unsaturated macrolactones like globalide and ambrettolide were polymerized by enzymatic ROP. The clear advantage of the enzymatic process is that polymerizations of macrolactones occur very fast as compared to the chemically catalyzed reactions [13]. Thermal crosslinking of the unsaturated polymers in the melt yielded insoluble and fully amorphous materials (Fig. 3, right). 

Chapter 4 shows that the range of polymeric structures from enzymatic polymerization can be further increased by combination with chemical methods. The developments in chemoenzymatic strategies towards polymeric materials in the synthesis of polymer architectures such as block and graft copolymers and polymer networks are highlighted. Moreover, the combination of chemical and enzymatic catalysis for the synthesis of unique chiral polymers is discussed. 

Complementary observations of the aftereffects of enzymatic hydrolysis on the graft copolymers show spatiotemporally controlled degradation, leading to a new method for fine surface abrasion as well as for degradation-rate regulation of polymeric materials. 

In certain forms of the material, the microporous polymer creates exactly two distinct, interwoven but disconnected porespace labyrinths, separated by a continuous polymeric dividing wall. This opens up the possibility of performing enzymatic, catalytic or photosyndietic reactions in controlled, ultrafinely microporous polymeric materials with the prevention of recombination of the reaction products by their division into the two labyrinths. These features combine with specific surface areas for reaction on the order of lO -lO square meters per gram, and with the possibility of readily controllable chirality and porewall surface characteristics of the two labyrinths. 

The present review describes recent developments on in vitro polymer production using an isolated enzyme as catalyst via nonbiosynthetic pathways (enzymatic polymerization). Beyond the in vivo relationship of the key-and-lock theory, in vitro catalysis of enzymes allowed structural variation of monomers and polymers, leading to not only natural polymers but unnatural polymers including new useful materials. In many cases, enzymes catalyzed highly enantio-, regio-, and chemoselective as well as stereoregulating polymerizations to produce a variety... 

Recombinant DNA technology and bacterial fermentation techniques have enabled the design of artificial genes and the production of artificial protein materials. Typically a peptide repeating sequence is designed and translated into a DNA sequence. The DNA monomer is chemically synthesized and enzymatically polymerized and cloned into a bacterial vector or a plasmid, which is later transferred into a bacterial host to express the coded protein polymer. Because the protein products are genetically coded in the DNA sequences. 

Studies on enzyme-catalyzed polymerization ( enzymatic polymerization ) has been of increasing importance as a new trend in macromolecular science. Enzyme catalysis has provided a new synthetic strategy for useful polymers, most of which are difficult to produce by conventional chemical catalysts. Enzymatic polymerization also affords a great opportunity for use of nonpetrochemical renewable resources as starting substrates of functional polymeric materials (as shown in the industrial examples cited above). 

In enzymatic polymerizations the product polymers can be obtained under mild reaction conditions without using toxic reagents. Therefore, enzymatic polymerization has great potential as an environmentally friendly synthetic process of polymeric materials, providing a good example of achieving sustainable polymer chemistry. ... 

Polypyrroles (PPy s) are formed by the oxidation of pyrrole or substituted pyrrole monomers. In the vast majority of cases, these oxidations have been carried out by either (1) electropolymerization at a conductive substrate (electrode) through the application of an external potential or (2) chemical polymerization in solution by the use of a chemical oxidant. Photochemically initiated and enzyme-catalyzed polymerization routes have also been described but are less developed. These various approaches produce polypyrrole (PPy) materials with different forms—chemical oxidations generally produce powders, whereas electrochemical synthesis leads to films deposited on the working electrode, and enzymatic polymerization gives aqueous dispersions. The conducting polymer products also possess different chemical/electrical properties. These alternative routes to PPy s are therefore discussed separately in this chapter. 

Enzymatic polymerization will have its greatest value when it uses renewable raw materials to make, under mild conditions, polymers that are biodegradable. It should avoid toxic chemicals and toxic catalysts. Some polymers that can be prepared in this way cannot be made by the usual chemical methods. 

The strict primer dependence of the glycogen phosphorylases makes them ideal candidates for the synthesis of hybrid structures of amylose with non-natural materials (e.g., inorganic particles and surfaces, synthetic polymers). For this, a primer functionality (maltooligosaccharide) can be coupled to a synthetic structure and subsequently elongated by enzymatic polymerization resulting in amylose blocks. 

Enzymatic polymerizations are a powerful and versatile approach which can compete with chemical and physical techniques to produce known materials such as commodity plastics and also to synthesize novel macromolecules so far not accessible via traditional chemical approaches. 

In this first textbook on the topic we aim to give a comprehensive overview on the current status of the field of sustainable, eco-efficient and competitive production of (novel) polymeric materials via enzymatic polymerization. Furthermore an outlook on the future trends in this field is given. 

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