Future Polymer Backbones

A summary of the strengths and weaknesses of current backbones against these criteria is presented in Table 2. 

As has been discussed, high vinylidene PIB is more thermally reactive, giving more process and formulation flexibility, but requires more expense and is thinner than conventional PIB. The OCP and PAO s have excellent 

This situation leads to several opportunities for improvement, two of which are (in the shorter term) to reduce the cost of high vinylidene PIB, and, (in the longer term) for maximal performance, to provide a backbone that has OCP/PAO-type performance at PIB cost. The first opportunity is discussed below. 

Besides reduced overall cost because of the simplified process and materials requirements, it also provides some improvement in thickening power lost from the BFs-produced material, while maintaining the good reactivity properties. However, this process is not yet fully developed, so the total costs are not yet fully certain. 

Another alternative backbone, this time moving to a more OCP/PAO-t3 e architecture, is shown in Fig. 10. 

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There are, however, things about the polymer structure which are not known for certain. We assume that the reaction occurs in a random manner along the polymer backbone but there is little evidence at all concerning this problem and a detailed analysis must await future research. In addition, we know very little about the effects of polymer tacticity on the reaction shown in Equation 21. This also remains to be studied. On the other hand, we are confident that this reaction does not lead to a novel crosslinking reaction sequence since these polymers are soluble in a number of different solvents (Table II). 

The ability to create molecular level actuators has been taken even further in the example of thiophene-based molecular muscles by Madden and Hunter. Conformational rearrangement of the polymer backbone in molecules such as calix[4]arene-bithiophene was created at the molecular level [118]. This work has recently been reviewed and prospects for future research in this area considered [119]. 

The main-chain type pyridine containing SMPU has so far not been fully investigated. In future studies, the pyridine ring will be attached to the polymer backbone as a pendant. Based on the hydrogen-bonded supramolecular stmcture, the BIN-SMPUs will have maity unique advantages due to their shape memory, mechanical and damping properties. 

In conclusion, polymer electrolytes based on phosphazene backbone and containing ether side chains are, after complexation with alkali metal salts, among the highest ionically solvent-free polymer salt complexes, with conductivities in the order of 10" -10" S cm However, these conductivities are still below the value of 10 S cm" which is considered to be the minimum for practical applications. Therefore the design of new polyphosphazenes electrolytes with a higher conductivity and also a higher dimensional stability still remains a challenge for future researchers. 

The polyphosphazenes are high molecular weight polymers with a wide range of novel and potentially useful properties. The large number of different pendant groups with widely varied functionality which can be attached to the P-N backbone demonstrate the unusual molecular design potential of this class of polymers. Undoubtedly, some of these will hold promise for future research and development. 

P-N backbone demonstrate the unusual molecular design potential of this class of polymers. Undoubtedly, some of these will hold promise for future research and development. 

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