Polyesters segmented

Fig. 2. Sphemlitic moiphology of thermoplastic elastomer where the heavy lines represent polyester segments (184).

The diamide unit acts as a nucleation initiator for the polyester segments.24 The presence of these diamide units at low concentrations results in an increased crystallization temperature. With increasing diamide concentrations in the polyester, the Tg and Tm also increase. 

Carboxylated polyesters were prepared by extending hydroxyl-terminated polyester segments with dianhydrides. Carboxylated polyesters which were soluble in common lacquer solvents were effective in improving the adhesion of coatings on a variety of substrates when 1-10% was blended with cellulose acetate butyrate, poly(vinyl chloride), poly(methyl methacrylate), polystyrene, bisphenol polycarbonates, and other soluble polymers. 

Preparation of Carboxylated Polyesters. Hydroxyl-terminated polyester segments were prepared by conventional procedures and extended with an equimolar amount of dianhydride (2). To avoid the possibility of crosslintdng the polymer, reaction1 with the dianhydride was carried out at 175 °C. Depending upon the size of the reaction mixture, about 1 to 3 hours were required for all of the dianhydride to react and for a medium-to-high melt viscosity to be obtained. Inherent viscosities were 0.3 to 0.4. 

The carboxylated polyesters were prepared by a two-step process (1) preparation of a hydroxyl-terminated polyester segment and (2) reaction with a dianhydride to extend the polyester and introduce carboxyl groups. When the dianhydride is pyromellitic (II), the equation is as follows ... 

In addition to pyromellitic dianhydride (PMDA), three other dianhydrides were used to extend the polyester segments. These anhydrides were prepared by heating trimellitic arihydride (IV) with glycol diacetates (V) (6) ... 

The carboxyl content was determined by the molecular weight (length) of the polyester segment which was extended by the dianhydride—the greater the molecular weight (e.g., the value of m in formula VII), the lower the carboxyl content. The value of n was about 2 to 4 when the polyester segment molecular weight was about 3000 (m = 13). 

The fuel properties of the pyrolysis oil of an aliphatic polyether-segmented PU could be predicted by taking into account the linear and cyclic oxygenated saturated and olefinic hydrocarbon nature of the components. Elimination of the reactive and toxic diisocyanate from the pyrolysis oil of PU in a lower temperature pyrolysis step is easier in the case of polyether soft segment, because of the larger temperature difference of decomposition steps compared to that of polyester-segmented PU. 

AO containing various phenolic moieties were prepared by transesterification in the presence of tetraalkyl titanates. Randomly distributed -active moieties are characteristic of 140 (only the hard polyester segment is given) prepared from dimethyl terephthalate, 1,4-butanediol, poly(tetramethylene oxide)diol and dimethyl 5-(3,5-di-tm-butyl-4-hydroxybenzenepropaneamido)isophthalate [181]. The mentioned polymeric AO was used for stabilization of polyether-polyester elastomers. A partial attachement of tetrakis[methylene 3(3,5-di-tert-butyl-4-hydroxy-phenyl)propionate]methane (3) via transesterification reaction was expected in the synthesis of another polyether-polyester elastomer by [182]. A reversible redox polyester was formed from 2,5-bis(2-hydroxyethyl)hydroquinone and dichlorides of aliphatic dicarboxylic acids [137],... 

This reaction is often employed in the production of flexible urethane foams, which are frequently block copolymers of polyether or polyester segments joined to polyurea segments. (The polyester or polyether segments terminate in urethane segments resulting from reaction of polyether or polyester hydroxyl end groups with the isocyanate.)... 

Similarly, a polyurethane containing polyester segments is an effective adhesive for lamination of PET film to wood. The polyester segment of polyurethane is compatible with the polyester film surface while the urethane linkages provide hydrogen bonding interaction between adhesive and substrate (Diagram 12). 

In principle, the functionalization strategies presented may not be limited to fnnctionalization of polyesters. One can, for instance, envisage the incorporation of polyester segments as chain extenders of soft segments in poly(urethanes), thereby providing access to functional groups in an important class of biomaterial especially for cardiovascular applications. 

Synthesis and Characterization of Block Copolymers Containing Poly(aryl ester ketone) and Liquid Crystalline Polyester Segments. Chem. J. Chin. Univ, 26(3), 589-591. 

AU Polyurethane elastomer with polyester segments (ASTM)... 

Condensation polymerization and stepwise addition polymerization are, for example, applied for the preparation of block polyesters. The synthesis concepts are different from those of chain polymerization in that at least one monomer is an oligomer with one or two functional end groups, for example polytetrahy-drofurane with a molecular weight of several hundred and OH-end groups (see Example 3.23). If this oligomer partially replaces butandiol in the condensation polymerization with terephthalic acid (compare Examples 4.1 and 4.2), a poly(ether ester) is obtained with hard polyester segments and soft polyether segments and with the properties of a thermoplastic elastomer. 

On the other hand, block copolymers containing aliphatic polyester segments are usually synthesized by a dual initiator (Figure 1(b)). Accordingly, the first segment is synthesized by AROP and subsequently employed as a macroinitiator for ATRP. In this transformation, PCL is the most commonly used aliphatic polyester obtained by AROP. A typical example was reported by Jakubowski et who polymerized CL by a dual initiator, 2-hydroxyethyl 2-bromoisobutyrate, in the presence of tin(II) ethyl hexanoate. Extension of the chain with ODMA and DMAEMA using ATRP technique resulted in the formation of the corresponding block copolymers (Scheme 38). Some other difunctional or dual initiators have also been employed for AROP of cyclic esters. 

In these polyester TPEs, the hard polyester segments can crystallize, giving the polymer some of the attributes of semicrystalhne thermoplastics, most particularly better solvent resistance than ordinary rubbers, and also better heat resistance. Above the melting temperature of the crystalhne regions, these TPEs can have low viscosity and can be molded easily in thin sections and complex stmctures. Properties of thermoplastic polyester elastomers can be fine-tuned over a range by altering the ratio of hard to soft segments. 

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