Functionalized polyesters polycarbonates

Nearly all of the polymers produced by step-growth polymerization contain heteroatoms and/or aromatic rings in the backbone. One exception is polymers produced from acyclic diene metathesis (ADMET) polymerization.22 Hydrocarbon polymers with carbon-carbon double bonds are readily produced using ADMET polymerization techniques. Polyesters, polycarbonates, polyamides, and polyurethanes can be produced from aliphatic monomers with appropriate functional groups (Fig. 1.1). In these aliphatic polymers, the concentration of the linking groups (ester, carbonate, amide, or urethane) in the backbone greatly influences the physical properties. 

As with Volume 1 in the series, this Chapter will deal specifically with polyesters, polycarbonates, polyamides, and polyimides. The four groups form a cohesive unit for a number of reasons the kinetics and techniques of synthesis are frequently similar, indeed the same difunctional reagents appear repeatedly as starting materials for synthesis, and their characteristic functional groups form an integral part of the polymer backbone. 

This Chapter deals with polyesters, polycarbonates, polyamides, and polyimides. These have been defined as those linear systems in which the characteristic functional groupings are present within the main chain. Thus, polymers such as poly(methyl methacrylate) and poly(acrylamide) are specifically excluded, as are peptides and proteins which are considered in other Specialist Periodical Reports published by the Chemical Society. 

Functionalization of more polar hydroxytelechelic polymers with the synthon resulted in comparably spectacular changes in material properties. Functionalized polyether is a material with a broad rubber plateau in DMTA, and a storage modulus of 10 MPa, whereas the starting material is a viscous liquid. The properties of functionalized polyester and functionalized polycarbonate are those of semicrystalline polymers, whereas the starting materials are very brittle. 

The specialty class of polyols includes poly(butadiene) and polycarbonate polyols. The poly(butadiene) polyols most commonly used in urethane adhesives have functionalities from 1.8 to 2.3 and contain the three isomers (x, y and z) shown in Table 2. Newer variants of poly(butadiene) polyols include a 90% 1,2 product, as well as hydrogenated versions, which produce a saturated hydrocarbon chain [28]. Poly(butadiene) polyols have an all-hydrocarbon backbone, producing a relatively low surface energy material, outstanding moisture resistance, and low vapor transmission values. Aromatic polycarbonate polyols are solids at room temperature. Aliphatic polycarbonate polyols are viscous liquids and are used to obtain adhesion to polar substrates, yet these polyols have better hydrolysis properties than do most polyesters. 

Lipase is an enzyme which catalyzes the hydrolysis of fatty acid esters normally in an aqueous environment in living systems. However, hpases are sometimes stable in organic solvents and can be used as catalyst for esterifications and transesterifications. By utihzing such catalytic specificities of lipase, functional aliphatic polyesters have been synthesized by various polymerization modes. Typical reaction types of hpase-catalyzed polymerization leading to polyesters are summarized in Scheme 1. Lipase-catalyzed polymerizations also produced polycarbonates and polyphosphates. 

The functional groups that typically participate in this type of polymerization are carboxyl, amine, and alcohol groups. Examples of step growth polymers include polyesters and nylons, which are often spun into fibers used to manufacture carpeting and fabrics, and polycarbonates, which are converted into compact discs, jewel cases, and the large bottles used in water coolers. 

A cumulative success of artificial ion-channel functions by simple molecules may disclose a wide gate for the design of ion channels and possible applications to ionics devices. Incorporation of these channels into bilayer lipid membrane systems may trigger the developments towards ionics devices. The conventional BLM system, however, is not very stable, one major drawback for the practical applications, and some stabilization methods, such as impregnating the material in micro-porous polycarbonate or polyester filters, are required. On the other hand,... 

Polycarbonates and Polyurethanes The chemistry of carbonic acid derivatives is particularly important because two large classes of polymers are bonded by linkages containing these functional groups the polycarbonates and the polyurethanes. Polycarbonates are polymers bonded by the carbonate ester linkage, and polyurethanes are polymers bonded by the carbamate ester linkage. Lexan polycarbonate is a strong, clear polymer used in bulletproof windows and crash helmets. The diol used to make Lexan is a phenol called bisphenol A, a common intermediate in polyester and polyurethane synthesis. 

Because of the high functionality of glycerol it is not surprising that a significant amount of research has focused on new polymeric materials that incorporate glycerol (Fig. 8.4). This includes polyesters, poly ethers, and polycarbonates (Ray and Grinstaff, 2003 Fu et al., 2003). In addition to the linear and network polymers, dendritic or hyperbranched structures have been investigated extensively (Malmstrom et al., 1995 Hawker et al., 1997 Jayaraman and Frechet, 1998 Bosnian et al., 1999 Sunder et al., 1999, 2000 ... 

Besides the use of micromolecular multiinitiators, block copolymers can be obtained from macromolecular initiators. In a first step, a polymeric initiator is generally synthesized by reacting a mono- or difunctional polymer with a functional initiator. Various macromolecular initiators were prepared in this way including quite different sequences polystyrene [13, 18, 19, 25, 26], poly(dimethylsiloxane) [27], polymethylmethacrylate) [13,15,28], polyvinylacetate [28], polyvinylchloride [29, 30], polyesters [30], polycarbonate [31,32], polybutadiene [13, 25, 33], polyamide [34], polyethylene glycol) [35] or polyaromatic [36], An excellent review of the synthesis and uses of such macroinitiators was written by Nuyken and Voit [37]. Thus, only few typical examples are going to be mentioned below. 

Hole transport in polymers occurs by charge transfer between adjacent donor functionalities. The functionalities can be associated with a dopant molecule, pendant groups of a polymer, or the polymer main chain. Most literature references are of doped polymers. The more common donor molecules include various arylalkane, arylamine, enamine, hydrazone, oxadiazole, oxazole, and pyrazoline derivatives. Commonly used polymers are polycarbonates, polyesters, and poly(styrene)s. Transport processes in these materials are unipolar. The mobilities are very low, strongly field and temperature dependent, as well as dependent on the dopant molecule, dopant concentration, and the polymer host This chapter reviews hole transport in polymers and doped polymers of potential relevance to xerography. The organization is by chemical classification. The discussion mainly includes molecularly doped, pendant, and... 

An example of how ab initio calculations may be applied to the study of fragments of polymer chains is given by Jaffe, Yoon, and McLean, who studied a series of mono- and diphenyl molecules containing up to 35 atoms. These compounds are models for a variety of important polymers such as polycarbonates (see Figure 1), polyimides, aromatic polyamides, aromatic polyesters, and polyether sulfone. A variety of basis sets, representing linear combination of Gaussian functions to approximate Slater-type orbitals (STOs) as compiled in Table 1, were employed. 

This polymerization process is a polycondensation in which the molecular weight builds up slowly as the small molecules of water are eliminated. Most step polymerization processes are polycondensations thus the terms step polymerization and condensation polymerization are often used synonymously. The stepwise reaction leads successively from monomers to dimers, trimers, and so on, until finally polymer molecules are formed. The polymers obtained are classified by taking into account the functional group of the repeating unit, for example, polyesters (— CO —O—), polyamides ( — CO— NH —), polyurethanes (—O — CO — NH —), polyethers ( — O —), and polycarbonates ( — O — CO —O —). 

The author worked for many years at BP Research on the synthesis of LCPs and devised an empirical method called the Mesogenic Index, which employs functional group contributions on an additive score basis to predict whether a particular random copolymer is likely to exhibit a mesophase (subject to the polymer being soluble or fusible). This chapter explores the general features and theoretical aspects of the chemical structures of main chain LCPs and describes the Mesogenic Index and how it was successfully applied to polyesters, polyamides and polycarbonates. The final section describes the extension of the MI empirical method to the various types of LC polyimides reported in recent years. 

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