Polymers experimental background

A third way authors establish importance as they share background information is to highlight the need for new knowledge. Few scientists can resist the appeal of new knowledge, and a project will likely be successful if it has the potential to offer new insights, depth, or detail. For example, Fairbrother (excerpt 12R) uses this approach when he states that the surface science associated with polymer modihcation treatments remains virtually unexplored. He goes on to cite a panel report that attests both to this lack of mechanistic understanding and to the need for concerted experimental research in this area. 

Before considering the experimental aspects of shake up phenomena in polymers it is worthwhile briefly considering some of the theoretical background since this provides considerable insight into the processes involved. 

There is overwhelming evidence that the aramide fibres possess a radially oriented system of crystalline supramolecular structure (see Fig. 19.1). The background of the properties, the filament structure, has been studied by Northolt et al. (1974-2005), Baltussen et al. (1996-2001), Picken et al. (2001), Sikkema et al. (2001, 2003), Dobb (1977-1985) and others. The aramid fibres (and the "rigid" extended chain fibres in general) are exceptional insofar as they were - with the rubbers - the first polymer fibres whose experimental stress-strain curve can very well be described by a consistent theory. 

In this chapter, a selective overview of technological and historical background is followed by a general discussion of the microscopic details of the transport phenomenon and experimental techniques. Key results of earlier studies on carbon-based systems are presented and then compared with corresponding data on poly(methylphenylsilylene) (PMPS), which has been taken as the prototype for studies of transport system in polymers with silicon backbones. Key points are then summarized. Those wishing to omit the extensive background section may proceed directly to the section on electronic transport in polysilylenes (page 492). 

Time-resolved fluorescence depolarization studies have, over the past decade, provided an interesting method for monitoring molecular reorientational motions in solution. The technique has been applied to investigations of both nthetic polymers and macromolecules of biological interest, and a selection of the results of these are discussed here. However, until recently, the relatively pc r quality of much of the data available from these measurements has precluded detafled quantitative interpretations of the results. With the advent of improved experimental techniques for fluorescence decay time determinations due in part to the availability of pulsed lasers for sample excitation and more accurate data analysis procedures, it is envisaged that interest in the technique may be revived. We will present here a short recapitulation of the background to these experiments, following from Sect. A. V. 

Recently, the cationic polymerization of formaldehyde in CO2 (60% formaldehyde) has been studied [36, 37]. The monomer/C02 mixture was prepared by decomposing a-polyoxymethylene at 150—180°C in a CO2 atmosphere. About 0.8 wt. % methanol, and 1.2 wt. % water were present as impurities. The experimental results and theoretical conclusion must be measured with the knowledge of this background. The uncatalysed reaction was studied (under pressure) from 20° to 50°C. Polymer yields after 10 min increased from 3 wt. % to 25 wt. % and the DP from 300 to 720. The authors interpreted these results as indicating an increase in the initiating species and the promotion of the rate of propagation. 

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