Polyether-segmented polyamide

HEMA-Styrene Triblock Copolymers and Polyether-Segmented Polyamide... 

Table 4.4 Carbon dioxide (A)/nitrogen (B) permselectivity characterization for polyimide, polyurethane and polyamide block-copolymers containing polyether segments.

N. Yui, K. Kataoka, T. Okano, Y. Sakurai, K. Sanui, and N. Ogata, Microstructure of polyether-segmented polyamides and its role in antithtombogenicity, in "Biological and Biomechanical Performance of Biomaterials, Advances in Biomaterials 6," P. Christel, A. Meunier, and A.J.C. Lee, ed., Elsevier, Amsterdam (1986). 

Poly(amide-b-ethylene oxide) copolymers were presented in 1990 as a promising membrane material [43]. These block copolymers were developed in 1972 but in 1981 began to be used for commercial purpose under the trade name Pebax , produced by ATOCHEM [44] (now ARKEMA). Another important group of segmented poly(ester)s used for membranes are block copolymers based on PEO and PBT (poly(butylene tereph-thalate), known under commercial name of Polyactive [45]. By changing the polyamide and polyether segment, molecnlar mass and the content of each block, the mechanical, chemical, and physical properties are nicely tnned as well [46]. 

The permeability of water vapor through PET is higher than that of polyolefins but lower than that of polycarbonate, polyamide, and polyacetal. Antioxidants are necessary to prevent to the oxidation of polyether segments in thermoplastic polyester elastomer. Chemical resistance of PET is generally good to acids, alkalis, and organic solvents. 

Polyamide TPEs are usually either polyester-amides, polyetherester-amide block copol5nners, or polyether block amides (PEBA) (see Fig. 3.7). PEBA block copol5nner molecular architecture is similar to typical block copol5nners. The polyamide is the hard (thermoplastic) segment, while the polyester, polyetherester, and polyether segments are the soft (elastomeric) segment. ... 

The PEBA are produced by a aiolten state polycondensation reaction of a dicarboxylic polyamide and a polyether diol. The reaction of the rigid polyamide (hard) segments and amorphous polyether (soft) segments in the presence of heat, vacuum and catalyst yields the polyether block amide with the general formula shown below. 

In this formula, PA represents the polyamide segment and PE represents the polyether segment. As shown in the general formula, the polyether block amide consists of a linear chain of polyamide and polyether segments (blocks) in an ordered pattern. 

The relative amounts of polyamide and polyether determine the hardness and flexibility of the copolymer. This allows for a range of polymers with different flexibilities to be produced using the same type of polyamide and polyether segments. 

Due to the diversity of polyether block amide thermoplastic elastomers that can be produced, a discussion of their specific properties would be a rather lengthy exercise. Even to list the properties of all the possible combinations of a particular set of polyamide and polyether segments could prove cumbersome as the amount of either segment in the copolymer may vary between ten and ninety percent. Therefore, a discussion of the properties of PEBA can be best accomplished by citing overall performance characteristics and ranges of values. Several properties worth noting include ... 

The great majority of thermoplastic elastomers (TPE) are copolymers associating soft and hard blocks, such as polyamide- -polyethers, poly urethane-6-polyethers, or polyether-6-polyesters. However, polymers with less classical structures, such as liquid crystalline copolymers or block copolymers based on supramolecular segments, are the subject of extensive research and will probably be commercialized in the near future. 

Dimerized fatty acids (DFA) can be used as an alternative to polyether segments in TPE. The polyester elastomers based on DFA were first prepared by Hoeschele [42]. The properties affecting the degradation stability were improved, but the properties at lower temperatures were unsatisfactory, because the higher glass transition temperature was influenced by the lengths of the amorphous segments. DFA can be coupled with diols and diamines to synthesize telechelic polyesters (Scheme 14) and polyamides, respectively. 

The polyamide and the polyether segments are usually incompatible, phase separation often occurs and the reaction between the reactive chain-ends can only take place at the interface. This reaction can be accelerated by using very reactive functional groups, such as acid halides. The synthesis of polyamides and polyesters via interfacial polymerization has been extensively reviewed by P. W. Morgan [43] in the mid-sixties. A few years later, Castaldo et al. [44] successfully synthesized a poly(ether ester amide) based on PA6.6 and PEO. The a,oj-dihydroxy polyether was first reacted with a diacid chloride for several hours, either in the bulk or in chloroform, and at a rather low temperature (60-90°C). The mixture was then poured into a vigorously stirred aqueous solution of diamine and sodium hydroxide. Later, de Candia et al. [45] reproduced this technique to study the physical and mechanical properties of the copolymer. The same polymerization technique was also used to prepare copolymers based on PPO as the polyether segment and PA6.10 as the polyamide block [3,46,47]. 

The thermal polymerization of polyamide and polyether segments with the formation of an amide link has been repeatedly described in the literature and numerous patents have been filed by companies, such as Toray Industries, Teijin Ltd., and Asahi Kasei. For instance, Kimura et al [58] successfully prepared a poly(ether-amide) copolymer by polymerizing the nylon 6.6 salt together with the isolated salt of a poly(oxyethylene) diglycolic acid and 1,6-diamino-hexane, at 270 °C for 5 h in vacuum. 

Yui N, Tanaka J, Sanui K and Ogata N (1984) Polyether-segmented polyamides as a new designed antithrombogenic material Microstructure of poly (propylene oxide)-segmented nylon 610, Makromol Chem 185 2259-2267. 

Among the polyurethane, polyester, and polyamide thermoplastic elastomers, those with polyether-based elastomer segments have better hydrolytic stabihty and low temperature flexibiUty, whereas polyester-based analogues are tougher and have the best oil resistance (43). Polycaprolactones and aUphatic polycarbonates, two special types of polyesters, are used to produce premium-grade polyurethanes (12). 

Polyurethane-based FTPEs are produced by reacting fluorinated polyether diols with aromatic disocyanates. The resulting block copolymers contain fluorinated polyether soft segments.68 Another possible method of preparation of fluorinated TPE is dynamic vulcanization. Examples are a blend of a perfluoroplastic and a perfluoroelastomer containing curing sites or a combination of VDF-based fluo-roelastomers and thermoplastics, such as polyamides, polybutylene terephtalate, and polyphenylene sulhde.69 70... 

Poly(ether-b-amide). In these particular thermoplastic elastomers the hard blocks consist of aliphatic polyamides, whereas the soft segments are formed of aliphatic polyethers. 

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