Mechanical strength anhydride

Unsaturated polyester resins prepared by condensation polymerization constitute the largest industrial use for maleic anhydride. Typically, maleic anhydride is esterified with ethylene glycol [107-21-1] and a vinyl monomer or styrene is added along with an initiator such as a peroxide to produce a three-dimensional macromolecule with rigidity, insolubiUty, and mechanical strength. 

Recently, a new polyanhydride, poly(fatty acid-sebacic acid), has been synthesized. This polyanhydride uses hydrophobic dimers of erucic acid. Some of its physical properties relevant to the fabrication of drug delivery devices are also improved over those of the other anhydrides based on CPP lower melting temperature, higher solubility in solvents, and higher mechanical strength. The erosion of the polymers is dependent on... 

Fig. 50. Possible mechanism by which chains with multiple reactive sites can graft to an interface. This example, which would be typical of a maleic anhydride functionalized polymer reacting on a polyamide, shows on one side end-grafted chains and on the other side of the interface, a loop structure. The effect of this loop structure on the mechanical strength of the interface is not fully clear but loops that are too short will weaken the interface...

Aromatic polymides made by the condensation reaction of pyromellitic anhydride with aromatic diamines have attracted attention because of their high-temperature properties such as therm.al stability (in air at 811 K, in inert atmosphere at 1005 K) and good mechanical strength, as well as resistance to radiation damage [106, 107]. The generic structure conventionally assigned to these substances is that of a linear polyimide... 

This approach was considered because it would permit the synthesis of biomaterials (for drug delivery systems, sutures, artificial organs, etc.) which are derived from nontoxic metabolites (amino acids and dipeptides) while also having other desirable properties for example, the incorporation of an anhydride linkage into the polymer backbone could result in rapid biodegradability, an iminocarbonate bond may provide mechanical strength, and an ester bond may result in better film and fiber formation. 

The crosslinked triepoxides exhibit higher mechanical strength and higher heat resistance in comparison with the diepoxy ACECs. The heat resistance of acid anhydride cured triepoxides is particularly high. This feature is obviously caused by the higher crosslinking density. 

Structural defects. Eventually, the mechanical strength properties and - in many cases - heat resistance are adversely affected. The unfavourable influence of the extended structure of ACECs is stronger in the case of amine curing in comparison with crosslinking with acid anhydrides (Table 13). 

The composites based on the PFO resols cured ester type (UP-632, XXIV) and cychc acetal type (UP-612, XXVI) CECs exhibit higher mechanical strength and heat resistance in comparison with similar materials cured with dicarboxylic acid anhydrides [86]. 

Polyanhydrides have been developed into various systems with mainly bone tissue engineering applications in mind. These polymers have mechanical strength much lower than that of bone but have been combined with other polymers, such as poly(imide)s, to resolve this problem. Polyanhydrides have been developed into photo-cross-linkable systems, based on dimethacrylated anhydrides, and also injectable systems, but little interest into these polymers with regard to tissue engineering has been taken in the recent past [82]. 

Poly(vinyl alcohol) (PVA) is one of the hydrogels most often used in biomaterial applications. Because of the presence of excessive hydroxyl groups, PVA contained a significant amount of water. PVA was also claimed to have good mechanical strength. Another hydrogel, poly(2-hydroxyethyl methacrylate) (poly-HEMA), is well known for its excellent biocompatibility. xhe versatile biomedical applications of poly-HEMA are demonstrated by its uses in contact lenses, vitreous humor replacements and suture materials. To explore a new formulation and other usages of these two pol ers, we have copolymerized HEMA with PVA-MA (PVA esterified with maleic anhydride), the preparation and properties of this copolymer are discussed in this article. 

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