Poly matrix system

Fig. 8.2 Plot of increase in modulus against volume fraction for a wide variety of nanocarbon/poly-mer systems. Volume fractions calculated from reported mass fractions assuming specific gravities of 1.8, 2.1 and 1 for CNT, graphene and matrix, respectively. Short fiber data from [16] and [17]. Moduli of individual layer graphene (lTPa) and reduced-graphene oxide (250GPa) included for reference.

Kitchell JP, Wise DL. Poly(lactic/glycolic acid) biodegradable drug-polymer matrix systems. Methods Enzymol 1985 112 436-448. 

Dhawan S, Varma M, Sinha VR. High molecular weight poly(ethylene oxide)-based drug delivery systems. Part 1 hydrogels and hydrophilic matrix systems. Pharm Technol 2005 29(5) 72-74, 76-80. 

One particular hydrophobic polymer, EVAc, has been investigated extensively as a matrix system for protein delivery. This polymer is biocompatible, a major consideration because of the interest in developing systems for human health. Other classes of hydrophobic polymers, like silicone elastomers and polyurethanes, may also be useful for controlled protein delivery, although there are fewer examples available in the literature. Nondegradable, hydrophilic polymers, such as poly(2-hydroxyethyl methacrylate) [p(HEMA)], are also biocompatible but usually release proteins over a relatively short period. However, a few examples oflong-term release of peptides and proteins from hydrophilic polymers are available. Longterm release of peptides from devices that employ cross-linked p(HEMA) as rate-limiting barriers has been reported (Davidson et al, 1988). The use of hydrophilic polymers for protein release is discussed in more detail elsewhere in this volume. 

In practice, 1—10 mol % of catalyst are used most of the time. Regeneration of the catalyst is often possible if deemed necessary. Some authors have advocated systems in which the catalyst is bound to a polymer matrix (triphase-catalysis). Here separation and generation of the catalyst is easy, but swelling, mixing, and diffusion problems are not always easy to solve. Furthermore, triphase-catalyst decomposition is a serious problem unless the active groups are crowns or poly(ethylene glycol)s. Commercial anion exchange resins are not useful as PT catalysts in many cases. 

Conducting polymer composites have also been formed by co-electrodeposition of matrix polymer during electrochemical polymerization. Because both components of the composite are deposited simultaneously, a homogenous film is obtained. This technique has been utilized for both neutral thermoplastics such as poly(vinyl chloride) (159), as well as for a large variety of polyelectrolytes (64—68, 159—165). When the matrix polymer is a polyelectrolyte, it serves as the dopant species for the conducting polymer, so there is an intimate mixing of the polymer chains and the system can be appropriately termed a molecular composite. 

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