Silicone aromatic polyamides

Poojari, Y Clarson, S. J., Lipase-Catalyzed Synthesis and Properties of Silicone Aromatic Polyesters and Silicone Aromatic Polyamides. Macromolecules 2010,43, 4616-4622. 

The conventional copolymerization pathways to PDMS and PET copolymers are paved with difficulties due to both physical incompatibility and chemical convertibility issues with regard to the catalysts and temperatures used for esterification and transesterification reactions [22]. In particular, the strong acids typically used in esterification or transesterification reactions will break the siloxane bonds Si-O-Si unless great care is taken. In order to address this problem, a facile enzymatic synthesis of silicone aromatic polyester (SAPE) and silicone aromatic polyamide (SAPA) in toluene under mild reaction conditions has been reported [26, 27], as shown in Schemes 2.4 and 2.5. 

Scheme 2.5 Lipase (Novozym-435)-catalyzed synthesis of silicone aromatic polyamide (SAPA) by polyamidation of a,W-(diaminopropyl)-terminated poly(dimethylsiloxane) with dimethyl terephthalate in toluene at 80°C imder reduced pressure [27]. Reproduced with permission...

In dentistry, silicones are primarily used as dental-impression materials where chemical- and bioinertness are critical, and, thus, thoroughly evaluated.546 The development of a method for the detection of antibodies to silicones has been reviewed,547 as the search for novel silicone biomaterials continues. Thus, aromatic polyamide-silicone resins have been reviewed as a new class of biomaterials.548 In a short review, the comparison of silicones with their major competitor in biomaterials, polyurethanes, has been conducted.549 But silicones are also used in the modification of polyurethanes and other polymers via co-polymerization, formation of IPNs, blending, or functionalization by grafting, affecting both bulk and surface characteristics of the materials, as discussed in the recent reviews.550-552 A number of papers deal specifically with surface modification of silicones for medical applications, as described in a recent reference.555 The role of silicones in biodegradable polyurethane co-polymers,554 and in other hydrolytically degradable co-polymers,555 was recently studied. 

Fig. 15. Temperature dependence on the dielectric constant of various polymers at 75cps. (O) Polyhexamethyl-ene-adipamide 0.005 in ( ) Silicone-bonded samica 0.004 in (O) Cellulose 0.005 in ( ) Polyimide 0.0048 in ( ) Polyethylene 0.005 in ( ) Rubber hydrochloride 0.002 in (A) Polyethylene terephthalate (Melinex) 0.005 in (A) Polyethylene terephthalate (Mylar) 0.002 in (V) Polypropylene 0.010 in (A) Polytetrafluoroethylene 0.0075 in (X) Polystyrene 0.005 in (+) Aromatic polyamide 0.0027 in (1 in = 2.54 cm)...

All commercial separators so far have been made of polyolefins, but they provide only limited heat resistance. Research is now focusing on separators made of different materials which would offer superior heat resistance. These include heat-resistant rubber such as silicone mbber and fluororubber, aromatic polyamide resin, liquid crystalline polyester resin, heat-resistant resin containing polyoxyalkylene, and resin with cross-linked groups. Separators made of such materials are expected to demonstrate not only high temperature stability and safety but also superior ion transportation for better rate capability at high current discharge. 

The primary chemical classes from which adhesives are made include epoxies, acrylics, phenolics, urethanes, natural and synthetic elastomers, amino resins, silicones, polyesters, polyamides, aromatic polyheterocyclics, and the various natural products such as carbohydrates and their derivatives as well as plant- and animal-based proteins. Chemical class was once a relatively clean differentiator of adhesives, but so many adhesives now are hybrids, designed to take advantage of specific attributes of more than one chemical class or type of material. Hybridization can be accomplished by incorporating into an adhesive a nonreactive resin of a different chemical class adding another type of reactive monomer, oligomer,... 

The routes give, using well-known condensation and radical reactions, bakelites (I), polyazophenylenes (II), polyimides (III), polyurethanes (IV), nitro compounds and polyamides (V), aromatic polyethers and polyesters (VI), polychalcones (VII), polyphenylene sulfides (IX), ammonia lignin (X), carbon fibers (XI), silicones (XII), and phosphorus esters (XIII). In addition, radiation and chemical grafting can be used to obtain polymers of theoretical interest and practical use. Although the literature on the above subject is very large, there are comprehensive summaries available (1,28,69). 

In order to improve the solubility of aromatic polymers silicon-containing polymers have also been synthesized, by introduction of siloxane or silarylene linkages into polymer backbones such as polyamides, polybenzimidazoles and polyimides [50]. The resultant polymers show fair solubility in organic solvents but most of them have poorer thermal stability then their analogues without siloxane or silarylene linkages. 

In fact all these properties were unavailable in conventional materials but may be covered by aromatic and heterocyclic Unear and thermosetting resins such as acetylene terminated resins, bismaleimides, polyetherimides, polyamide-imides, polybenzimidazoles, pol3dmides, polyetherketones, pol3qjhenylquinoxalines, polyphenylensulfides, polysulfones derivatives, polyst5nylp3nidines, fluoropol3mers, silicones, etc. 

It was,and still is, a purpose of our work to illustrate the synthetic potential of "a-b monomers" in the field of aromatic polyethers, polyesters and polyamides (concentrating on polyesters in the present contribution). The preparation of star-shaped and hyperbranched polycondensates is plagued by side-reactions resulting in crosslinks, and thus, clean step-growth processes are a basic requirement for a successfid synthesis. In this connection the potential of silicon mediated polycondensations should be explored, because polycondensations of silylated monomers may be a cleaner process than that of the corresponding nonsilylated (protonated) monomers, for instance, because proton catalyzed side reactions, such as the Fries-rear-rangement, are avoided. 

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