Linear polymers structure

The single most important factor that determines whether a cyclic monomer can be converted to linear polymer is the thermodynamic factor, that is, the relative stabilities of the cyclic monomer and linear polymer structure [Allcock, 1970 Sawada, 1976]. Table 7-1 shows the semiempirical enthalpy, entropy, and free-energy changes for the conversion of cycloalkanes to the corresponding linear polymer (polymethylene in all cases) [Dainton and Ivin, 1958 Finke et al. 1956]. The Ic (denoting liquid-crystalline) subscripts of AH, AS, and AG indicate that the values are those for the polymerization of liquid monomer to crystalline polymer. 

Application of the Rietveld Whole-Fitting Method to Linear Polymer Structure Analysis... 

For n = 6, known compounds are confined to methylamine and ethylamine these are probably [MnA6]X2 species. Tetrakis species are better defined here than for NH3 and probably have [MnX2A4] monomeric structures but the most common stoichiometry is MnX2A2. These latter species probably have the linear polymer structure of (8). 

Another interesting structural variation has recently been reported298 as occurring in some mixed metal compounds of dithiooxalate, i.e. MMn(S2C202)2,7.5 H20 (for M = Ni and Cu). These have the linear polymer structure (112), with seven-coordinate Mn11. 

Historically, high-pressure free radical copolymerization has been used to produce highly branched, ill-defined copolymers of ethylene and various polar monomers. Although these materials are in production and extensively used throughout the world, the controlled incorporation of polar functionality coupled with linear polymer structure is still desired to improve material properties. Recent focus in this area has led to the development of new transition metal catalysts for ethylene copolymerization however, due to the electro-philicity of the metal centers in these catalysts, polar functional groups often coordinate with the metal center, effectively poisoning the catalyst. There has b een some success, but comonomer incorporation is hard to control, leading to end-functionalized, branched polyethylenes [44, 46]. These results are undesirable due to low incorporation of polar monomer into the polymer as well... 

Ethylene chlorohydrin is made from HCl and ethylene epoxide. When small amounts of 1,2,3-trichloropropane are added to the bis(2-chloroethyl)formal, some branching of the otherwise linear polymer structure is achieved. 

Multidecker sandwich structures can be classified in the forms shown in Fig. 3.21 (a) and (b) and contrast with the linear polymer structures discussed so far (Fig. 3.21 c). 

This chapter will focus on linear polymer structures composed of synthetic polypeptide or polypeptide-polymer systems formed in bulk. Our aim is to present an overview of bulk self-assembled structures from polypeptide-based conjugates, specifically diblock and triblock architectures. Recent advances in theoretical developments and the first phase diagrams of such kind of polypeptide rod-coil systems will be also presented. 

Polyblends are normally prepared with linear polymer structures. The fine structure mentioned above undoubtedly results from the imposition of crosslinks in both components. 

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