Crosslinked insoluble amorphous

A study has been presented that describes the use of an epoxy functional fatty acid, 9,10-epoxy-18-hydroxyoctadecanoic acid, extracted from birch Betula pendula) outer bark to produce renewable thermosets (93). An epoxy fatty acid was polymerized by enzyme catalyzed polycondensation utilizing Candida antarctica lipase B to form oligomers with degrees low of pol5merization up to 9. The crosslinked polyesters form insoluble, amorphous, and transparent films. So it was demonstrated that thermoset films with tailored properties can be effectively made using forest products. 

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. 

Dioxiranes derived from chiral ketones have been used extensively to promote the enantioselective epoxidahon of alkenes [60]. The first examples of immobilized chiral ketones for this reaction were reported by Sartori and Armstrong [61]. A modified racemic hopinone was supported onto amorphous sihca KG-60, mesoporous silica MGM-41, and 2% crosslinked PS, respechvely, to obtain the insoluble precatalysts 38a-c (Scheme 8.18). 

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... 

The DTA curves obtained on the previous system may be used confidently as a characterization index. This technique offers unique advantages over other instrumental methods, especially those involving insoluble and amorphous crosslinked epoxy systems which exhibit diffuse X-ray patterns and which, because of their inherent intractable physical state, do not give reproducible infrared spectra. 

The cortex is an amorphous and electron-dense layer composed of at least two sublayers which are abundant in keratin-like proteins and a highly insoluble protein termed cuticulin. The medial layer is a fluid-filled compartment that also contains fine collagenous fibers. In some species, the fluid contains hemoglobin. The composite basal layer contains crosslinked collagen fibers in two to three distinct sublayers which spiral around the nematode at an angle 75° to the longitudinal axis. 

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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