Polymethacrylic acid cross-linked

We have cited the case of epoxidation with peracids earlier in this book. A cross-linked polymethacrylic acid can, in principle, be treated with a sulphonic acid catalyst and H2O2 to give the peracid, which will allow epoxidation to be carried out in a convenient way, while the polymer can be reused. The key advantage is that the product stream does not contain an acid, which may be harmful in several ways. 

The structures of a number of synthetic hydrophilic polymers as a representative range of those commonly used are shown in Fig. 1. Many common hydrophilic polymers are based on methacrylate or acrylate backbones. One of the most common is polyacrylic acid, which forms the basis of many hydrogel materials (Fig. lA). Although simple polyacrylic acid is water soluble, it can be easily cross-linked to form an insoluble network polymer that still, however, retains high affinity for water and is capable of adsorbing large amounts of water to form hydrogels these are discussed later. Polymethacrylic acid-based polymers are similar in nature (Fig. IB). One of the most commonly used polymers for contact lenses, polyhydroxyethyl methacrylate, is based on a similar backbone (Fig. 1C). 

An electrochemical method projected for the determination of the effective volume of a colloidally dispersed polyelec-trolyte phase in aqueous media was evaluated. Experiments with the highly flexible Sephadex (carboxymethyldextran) gel and the more rigidly cross-linked polymethacrylic acid resin were performed for this purpose. With the well-defined resin (gel) phase it was possible to measure the polymer volume as a function of every experimental condition used to test fully the fundamental concepts on which the method is based. The results substantiate the validity of concepts developed. Application of this method for estimating the effective volume of weakly acidic (basic) polymers in solution seems worthy of further consideration. However, some modification of the treatment of the electrochemical data is necessary for polymeric sols, and this aspect is discussed briefly. 

No.7,26th March 2002, p.2667-75 THERMAL PROPERTIES OF CROSS-LINKED POLYISOPROPYLACRYLAMIDE, POLYMETHACRYLIC ACID, THEIR RANDOM COPOLYMERS, AND SEQUENTIAL INTERPENETRATING POLYMER NETWORKS Diez-Pena E Quijada-Garrido I Frutos P Barrales-Rienda J M CSIC... 

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