Crosslinked insoluble amorphous polymer

Various a-methylenemacrolides were enzymatically polymerized to polyesters having polymerizable methacrylic methylene groups in the main chain (Fig. 3, left). The free-radical polymerization of these materials produced crosslinked polymer gels [10, 12]. A different chemoenzymatic approach to crosslinked polymers was recently introduced by van der Meulen et al. for novel biomedical materials [11]. Unsaturated macrolactones like globalide and ambrettolide were polymerized by enzymatic ROP. The clear advantage of the enzymatic process is that polymerizations of macrolactones occur very fast as compared to the chemically catalyzed reactions [13]. Thermal crosslinking of the unsaturated polymers in the melt yielded insoluble and fully amorphous materials (Fig. 3, right). 

Molecular weights of 30,000-60,000 could be obtained. The polymers showed outstanding thermal stability (TGA 550°C. break, air or nitrogen), are all soluble in common organic solvents (up to 15 wt. % ), form clear films, are colorless, and amorphous. The thermal decomposition of these polymers has been shown to take place by the loss of pendant phenyl groups as phenyl radicals. Thus, the thermal treatment of a film under nitrogen produces a crosslinked film which is still amorphous but insoluble no appreciable main chain degradation takes place. 

The potential applications for conducting polymers are enormous and this has stimulated a large amount of research into this area. Not surprisingly, solid-state NMR spectroscopy has been applied to study these amorphous, insoluble and in many cases crosslinked materials [24]. Looking at the CP/MAS spectra of a series conducing polyacenic polymers, some of which were doped with iodine, it was possible to see the effect of the halogen upon conductivity. These resins were prepared by a conventional procedure for the preparation a Novolak-type phenol-formaldehyde resin. After synthesis, the phenol-formaldehyde resin were dissolved and solutions were cast as a film and heat treated to between 590-670°C in a N2 atmosphere to form the polyacenic film. The electrical conductivity of the films was shown to increase... 

Although the photoinitiator is readily soluble in the monomer(s), it is insoluble in the polymer. Thus, Lucirin TPO precipitates and forms an amorphous core surrounded by a polymeric shell. The encapsulation efficiency, which is the ratio of encapsulated material to material initially added to the system, was determined to be about 90%. The release of the initiator into the environment was investigated using isopropanol as solvent. Compared to a 50% release of Lucirin TPO after less than 1 min, the release from a crosslinked shell is significantly prolonged to about 5 min. 

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