Simple Homopolymer Systems

This section is primarily concerned with the behaviour of simple homo-polymers. The development of viscoelastic theory was intimately linked with the study of polymeric species. This area of activity has led the way in the development of rheological models and experimental design and so is a very important area for the proto-rheologist to understand. So far in this chapter we have taken the approach of developing phase diagrams from a rheological perspective in order to understand linear viscoelastic 

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Simple homopolymers, where monodisperse standards and suitable solvents are available, are easily characterized by SEC. Homopolymers for which no monodisperse standards are available additionally require some more elaborate detection system for transformation of the retention time into molecular weight. This can be done by, e.g., universal calibration. Alternatively, an absolute molar mass detector, like an on-line light scattering detector or mass spectrometer, can be used. 

Most of the experiments reported so far have been performed on linear homopolymer systems. In Chap. 6 we discuss what has been achieved so far beyond such simple materials. We begin with the discussion of neutron spin echo data on miscible polymer blends, where the main issue is the dynamic miscibility . There are two questions Firstly, on what length and time scales and to what extent does a heterogeneous material like a blend exhibit homogeneous dynamics Secondly, how does it relate to the corresponding homopolymer properties ... 

Selected unsaturated carboxylic acids are particularly useful as coupling agents for calcium carbonate-type fillers. They interact strongly with the basic surface of the carbonate, unlike silanes that only show a weak interaction. In addition, unlike simple saturated carboxylic acids, which just have a beneficial effect on impact strength, unsaturated carboxylic acids may increase tensile strength. Table 6.5 illustrates this effect in a 60% filled CaCOs/PP homopolymer system. This system is heavily stabilized with both hindered phenol and phosphite-type antioxidants, and a small amount of peroxide was therefore added. 

D. T. Clark From studies of simple homopolymers, line widths and line shapes may be established for individual core levels. Our line shape analysis then follows a logical procedure starting from the simplest (0.5 sec) to the most complex (300 sec) fluorinated samples making use of calculations on model systems and experimental data from homopolymers to assign binding energies to the possible structural features. The procedure has been discussed elsewhere. ... 

The development of any science depends upon the ability of its practitioners to communicate in precise terms and to retrieve information from original and secondary sources without loss or distortion of meaning. These requirements would ordinarily presuppose the existence of a pertinent lingua franca. Even for relatively simple homopolymers, however, nomenclature and classification presents a complex and incompletely resolved problem, and no generally accepted system yet exists for the naming of block copolymers so as to describe precisely their chemical composition and molecular structural organization. Some examples of the difficulties are given below. 

Based on the previous discussions, it should be clear that although simple homopolymers are attractive as resists due to their ease of manufacture, compositional control, and molecular weight control, it is difficult to find a single homopolymer that satisfies the many requirements desirable in an e-beam resist. As a result various copolymers and terpolymers have been investigated in an attempt to optimize over the set of desirable properties including etch resistance and sensitivity. One product of such efforts has been styrene-acrylate copolymers, which have been in fact turned into highly successful e-beam resists. The basic idea in these systems has been to incorporate the good etch resistance provided by the incorporation of styrene into the copolymer with... 

Polymers have inherently high hydrocarbon ratios, making liquefaction of waste plastics into liquid fuel feedstocks a potentially viable commercial process. The objective is to characterise the thermal degradation of polymers during hydrogenation. LDPE is studied due to its simple strueture. Isothermal and non-isothermal TGA were used to obtain degradation kinetics. Systems of homopolymer, polymer mixtures, and solvent-swollen polymer are studied. The significant variables for... 

The system presented here can be applied to almost all homopolymers, copolymers and others, such as networks. However, generic source-based nomenclature should not be considered as a third nomenclature system to be added to the other two systems of nomenclature it must be considered as an auxiliary system and a simple extension of current source-based nomenclature. When the generic part of the name is eliminated from the name of a polymer, the well-established source-based name remains. 

Since the relaxation mechanisms characteristic of the constituent blocks will be associated with separate distributions of relaxation times, the simple time-temperature (or frequency-temperature) superposition applicable to most amorphous homopolymers and random copolymers cannot apply to block copolymers, even if each block separately shows thermorheologically simple behavior. Block copolymers, in contrast to the polymethacrylates studied by Ferry and co-workers, are not singlephase systems. They form, however, felicitous models for studying materials with multiple transitions because their molecular architecture can be shaped with considerable freedom. We report here on a study of time—temperature superposition in a commercially available triblock copolymer rubber determined in tensile relaxation and creep. 

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