Residual Functionality Research Articles

Use of the Kaiser Oxime Resin in the Solid-Phase Synthesis of 3-Aminobenzisoxazoles

Use of the Kaiser Oxime Resin in the Solid-Phase Synthesis of 3-Aminobenzisoxazoles

Multimodal imaging of residual function and compensatory resource allocation in cortical atrophy: a case study of parietal lobe function in a patient with Huntington's disease

In a case of Huntington's disease (HD) with dementia and pronounced parieto-frontal atrophy, the functional state of the affected regions was investigated using functional magnetic resonance imaging (fMRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET). It was observed that although parietal areas showed extensive atrophy and reduced resting glucose metabolism, the patient performed with similar accuracy but with longer response time in a visuospatial task compared with healthy control subjects. At the same time, the blood oxygen level-dependent (BOLD) fMRI signal in these areas, which are involved in visuospatial processing, showed a similar task-dependent modulation as in control subjects. The signal amplitude (signal percent change) of the task-dependent activation was even higher for the HD patient than in the control group. This residual functionality of parietal areas involved in visuospatial processing could account for the patient's performance in the task concerned, which contrasted with his poor performance in other cognitive tasks. The increased percent-signal change suggests that a higher neuronal effort was necessary to reach a similar degree of accuracy as in control subjects, fitting well with the longer reaction time. We propose that fMRI should be considered as a tool for the assessment of functionality of morphologically abnormal cortex and for the investigation of compensatory resource allocation in neurodegenerative disorders.

A highly acid labile silicon linker for solid phase synthesis

Abstract A novel arylsilane based linker has been prepared for the solid phase synthesis of small molecule combinatorial libraries. Efficient cleavage is achieved using TFA via anchimerically assisted protiodesilylation to yield aromatic products possessing no residual linker functionality.

Bulk copolymerization of methacryloyloxypropyl functionalized siloxane macromonomers with styrene: 1. Network formation

An α,ω-(3-methacryloyloxypropyl dimethyl siloxane) macromonomer (I) with a molecular weight of 3700 g mol−1 was copolymerized with styrene in bulk at 60°C using azobisisobutyronitrile as the initiator. Phase separation during polymerization was monitored macroscopically by clouding and microscopically by domain formation. The copolymer was separated into hexane soluble and insoluble fractions. From u.v., 1H n.m.r. and g.p.c. analysis of these fractions, the composition of the copolymers was determined as a function of feed composition (up to 50 wt% macromonomer) and reaction time (up to 6 h). Analysis of the hexane insoluble fraction showed that the macromonomer rapidly formed a crosslinked network copolymer with styrene, showing little residual functionality. The hexane soluble fraction contained a copolymer with blocks of dimers and trimers of I.

Network structure and properties of platinum‐catalyzed addition cure release coatings

AbstractSilicone‐release coatings are used by the pressure‐sensitive adhesive industry for labeling applications. Typical release coatings are prepared by the platinum‐catalyzed addition reaction of a silicone hydride fluid with a silicone vinyl polymer. Methodology has been developed to determine the network structure of cured release coatings, which involves degradation of the network with trifluoromethane sulfonic acid in excess hexamethyldisiloxane. Gas chromatography–mass spectrometry (GC–MS) and gas chromatography (GC) were employed to identify and quantify residual functionality and cross‐links. Residual hydride functionality was also determined by attenuated total reflectance–Fourier transform infrared spectroscopy (ATRFTIR). The observation of network structure by solid‐state 29Si‐NMR using cross polarization (CP) and magic angle spinning (MAS) is also discussed. The networks underwent a postcure as evidenced by a decrease in residual hydride functionality and an increase in silane content and/or cross‐links. © 1993 John Wiley & Sons, Inc.

The network structure of silicone release coatings

Silicone release coatings are used by the pressure-sensitive adhesive industry for labeling applications. A background discussion of silicone release coatings is presented. Methodology for determining the network structure of photolytically cured systems prepared by the cationic ring opening polymerization of an epoxy silicone fluid is described. Under typical polymerization conditions, these networks contain no unreached epoxides and have very low degrees of polymerization (D p), indicating that termination is competitive with propagation. A method has also been developed to determine the network structure of thermally cured systems prepared by the platinum-catalyzed hydrosilylation of silicone vinyl compounds with silicone hydrides. The nature of the cross-links and the types of residual functionality have been determined and the systems have been shown to undergo a postcure.