Polymers poly family

Eudragit (Rohm/Pharma Polymers, Darmstadt, Germany) is a class of polymer that will dissolve at specific pH values. Eudragit polymers are members of the poly(alkyl methacrylate) family of polymers. This family of polymers has a wide degree of properties due to the many modifications used in the formation of the polymers. The dissolution properties are based on the modification of the carboxylic moieties of methacrylic acid. The degree of modification and the specific modification determine at what pH and how quickly the polymers dissolve. 

The synthesis and characterization of four distinct families of poly (ortho esters) are described and designated as poly (ortho esters) I, II, III and IV. Poly (ortho ester) I is prepared by the transesterification of diethoxytetrahydrofuran with diols. Poly (ortho ester) II is prepared by the condensation of 3,9-bis (ethylidene 2,4,8,10-tetraoxaspiro [5, 5] undecane) with diols to produce a linear polymer or with a triol to produce a crosslinked polymer. Poly (ortho ester) III is prepared by the condensation of a flexible triol with and alkyl orthoacetate to produce ointment-like materials. Poly (ortho ester) IV is prepared by the condensation of a rigid triol with and alkyl orthoacetate to produce solid materials. The detailed mechanism of hydrolysis of these polymers has been determined and drug release data for a number of therapeutic agents are presented. 

The overall science around polyanhydrides is summarised in Figure 5.1. The main focus of this chapter is to introduce and provide an extensive review of the various promising aspects of one specific class of synthetic biodegradable medical polymer — poly anhydride. In the first part of the chapter the classification, chemical stmctures, and synthesis methods of various polyanhydrides are discussed. This is followed by a discussion of the in vitro and in vivo behaviour and degradation mechanism of these materials. Also, the various processing techniques that are employed are introduced and explained. Finally, medical applications of polyanhydride systems are presented, highlighting their role and their potential to be used as a family of medical polymers of the future generation . 

With the increasing concern of human society to environmental and energy problems, the family of microbial synthesized polymers poly(hydroxyalkanoates) (PHA) have been attracting more and more attention in both academic and industrial fields due to their complete biodegradability and the renewable carbon resources used to produce them (Doi, 1990 Muller, 1993). 

Poly(orthoesters) (POEs) constitute a class of amorphous, hydrophobic, biodegradable polymers. Different families of POEs have been reported (Figure 2.52). In addition to their surface wearing down mechanism, the rate of degradation of POEs is pH sensitive. They can be easily dissolved in organic solvents together with chloroform, methylene chloride, and dioxane owing to their hydrophobic nature [375]. 

Stmctures with the widest temperature range of demonstrated stabiUty have fluorine in the gamma position relative to siUcon (or further removed), as in CF2CH2CH2SiIlR R. Longer hydrocarbon chains, with or without hetero atoms, are feasible, but oxidative stabiUty is compromised and such materials are generally disfavored. Poly(3,3,3-trifluoropropyl)methylsiloxane [26702-40-9] demonstrates this stmctural principle. This polymer is one key member of the industrially important family of fluorosiUcone materials. 

Poly(l,3,4-oxadiazole) (POD) is a widely used isomei of the oxadiazole family of thermally stable polymers. The general stmcture of POD is... 

PBO andPBZT. PBZ, a family of/ -phenylene-heterocycHc rigid-rod and extended chain polymers includes poly(/)-phenylene-2,6-benzobisthiazole) [69794-31-6] trans-V 27V) and poly(/)-phenylene-2,6-benzobisoxazole) [60871-72-9] (ot-PBO). PBZT and PBO were initially prepared at the Air Force Materials Laboratory at Wright-Patterson Air Force Base, Dayton, Ohio. PBZT was prepared by the reaction of... 

Poly(arylene vinylenes). The use of the soluble precursor route has been successful in the case of poly(arylene vinylenes), both those containing ben2enoid and heteroaromatic species as the aryl groups. The simplest member of this family is poly(p-phenylene vinylene) [26009-24-5] (PPV). High molecular weight PPV is prepared via a soluble precursor route (99—105). The method involves the synthesis of the bis-sulfonium salt from /)-dichloromethylbenzene, followed by a sodium hydroxide elimination polymerization reaction at 0°C to produce an aqueous solution of a polyelectrolyte precursor polymer (11). This polyelectrolyte is then processed into films, foams, and fibers, and converted to PPV thermally (eq. 8). 

Another family of polyols is the filled polyols.llb There are several types, but die polymer polyols are die most common. These are standard polyether polyols in which have been polymerized styrene, acrylonitrile, or a copolymer thereof. The resultant colloidal dispersions of micrometer-size particles are phase stable and usually contain 20-50% solids by weight. The primary application for these polyols is in dexible foams where the polymer filler serves to increase foam hardness and load-bearing capacity. Other filled polyol types diat have been developed and used commercially (mainly to compete with die preeminent polymer polyols) include the polyurea-based PEID (polyhamstoff dispersion) polyols and the urethane-based PIPA (poly isocyanate polyaddition) polyols. 

The general approaches for the synthesis of poly(arylene ether)s include electrophilic aromatic substitution, nucleophilic aromatic substitution, and metal-catalyzed coupling reactions. Poly(arylene ether sulfone)s and poly(arylene ether ketone)s have quite similar structures and properties, and the synthesis approaches are quite similar in many respects. However, most of the poly(arylene ether sul-fone)s are amorphous while some of the poly(arylene ether)s are semicrystalline, which requires different reaction conditions and approaches to the synthesis of these two polymer families in many cases. In the following sections, the methods for the synthesis of these two families will be reviewed. 

Polymers like those in the poly aniline family interchange protons and anions with the solution, allowing a local modulation of pH. Composites that interchange cations allow the modulation of any cation concentration. Efforts are being devoted to the synthesis of polymer or polymeric derivatives having great cationic specificity. 

In view of these constraints, we recently suggested a different strategy for the improvement of the material properties of synthetic poly (amino acids) (12). Our approach is based on the replacement of the peptide bonds in the backbone of synthetic poly(amino acids) by a variety of "nonamide" Linkages. "Backbone modification," as opposed to "side chain modification," represents a fundamentally different approach that has not yet been explored in detail and that can potentially be used to prepare a whole family of structurally new polymers. 

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