摘要:

Charge-transfer polymerization is a new type of polymerization which has been developed within the last 20 years. Its essential character is the interaction between an electron donor (D) and an electron acceptor (A) involved in the initiating or/and propagating processes. Such polymerization has attracted a great deal of attention, mainly due to three factors. First, it proceeds through a novel type of initiating or propagating mechanism which has increasing interest for theoretical research. Second, since the charge-transfer interaction widely exists in organic compounds, a wide variety of compounds may be used as donors or acceptors in such polymerizations. Third, the charge-transfer interaction lowers the energy for the formation of reactive centers and so the polymerization may be carried out under more moderate conditions.

ISSN:1532-1797    

DOI:10.1080/07366578908055171

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The use of 13 carbon nuclear magnetic resonance (NMR) spectroscopy in the molecular characterization of macromolecules has advanced our knowledge into structural areas that have been nearly impossible to measure by other spectroscopic techniques. Innovative applications have led to determinations of polymer configurational distributions, comonomer sequence distributions, average sequence lengths, structure and distribution of short chain branches, and analyses of nonreactive end groups. As a result, the importance of 13C NMR to the field of polymer science cannot be overemphasized. The key to the success of 13C-NMR studies in defining polymer molecular structure has been a structural sensitivity which encompasses more than just a few functional groups or carbon atoms. A sensitivity to polymer repeat unit sequences of lengths from two to as many as five, seven, and even nine contiguous repeat units [1,2] has been observed. Of course, any structural technique that senses a unique response from as few as two successive repeat units will lead to a measurement of average sequence lengths [1,3] and run numbers [4]. In addition to this excellent structural sensitivity, there has been an enormous improvement in the quantitative sensitivity of 13C NMR in recent years. Detection of long-chain branching in polyethylene can now be made at a level of one per ten thousand carbon atoms [5], and newer generation of high field, higher sensitivity NMR spectrometers promise to extend this detection limit another order of magnitude.

ISSN:1532-1797    

DOI:10.1080/07366578908055172

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The molecular transport of small molecules through polymer films has been the subject of active research over almost three decades [1–8]. The main thrust in this area is either to accumulate a large body of experimental data to assess the stability of polymer films for extreme serviceability or to develop new theories which describe the phenomenology of transport processes, the latter often being studied in terms of three important parameters: permeation, diffusion, and solubility, in adition to the swelling phenomenon.

ISSN:1532-1797    

DOI:10.1080/07366578908055173

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The continuing demand for polymeric materials with a unique combination of properties has brought forth a sizable research effort concerning the use of trifluoromethyl substituents, particularly the 1,1,1,3,3,3-hexafluoroisopropylidene (HFIP) function derived from the incorporation of hexafluoroacetone (HFA) into the monomer. This work had its beginnings approximately 25 years ago when Rogers briefly reported in a patent the preparation of polyimides (PIs) from an hexafluoroisopropylidenebrideged diamine [1,2]. Since then numerous efforts have been made toward the synthesis, characterization, and evaluation of CF3-containing polymers. Much of this information is found in patents, indicating the importance of these polymers to industry. At the present time, at least 11 known classes of polymers containing pendant or backbone-incorporated bis-trifluoromethyl groups have been reported. These polymers show promise as film formers, gas separation membranes, seals, soluble polymers, coatings, and in other high-temperature applications. Frequently the polymer properties imparted by the inclusion of the HFIP function encompass: increased solubility, flame resistance, glass transition temperature, thermal stability, oxidation resistance, and environmental stability; decreased color, crystallinity, dielectric constant, and water absorption.

ISSN:1532-1797    

DOI:10.1080/07366578908055174

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1532-1797    

DOI:10.1080/07366578908055170

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor