Polymer microstructuring

A. Halperin, M. Tirrell, T. P. Lodge. Tethered chains in polymer microstructures. Adv Polym Sci 100 21-11, 1992. 

Analyses of polymer microstructures do not allow these possibilities to be unambiguously distinguished, However, EPR experiments demonstrate that radicals add exclusively to one of the terminal methylenes.87... 

Tonelli, A.E. NMR Spectroscopy and Polymer Microstructure VC1I New York, 1989. 

Secondly, new techniques have been developed which allow a more detailed characterization of both polymer microstructures and the kinetics and mechanism of polymerizations. This has allowed mechanism-structure-property relationships to be more rigorously established. 

Fig. 1A-L. Examples of polymer microstructures comprising tethered chains...

Tonelli AE (1989) NMR spectroscopy and polymer microstructure the conformational connection. VCH, Weinheim... 

Halperin A, Tirrell M, Lodge TP (1991) Tethered chains in polymer microstructure. In Adv Polym Sci, this volume... 

By designing the repeat unit into the parent diene (containing either an alkyl branch or functionality), only a single type of repeat unit is formed upon polymerization, giving pure polymer microstructures. To date, perfectly controlled ADMET ethylene copolymers have included ethylene-CO,34 ethylene-vinyl alcohol,35 ethylene-vinyl acetate,36 and ethylene-propylene.20 Figure 8.12... 

Thermal Behavior of Precisely Placed Branches in ADMET Polymer Microstructures... 

ADMET polymer microstructures, thermal behavior of precisely placed branches in, 447-450 ADMET polymers... 

Measurements of polymerization rate and parallel measurements on the resultant polymer microstructure in the butadiene/DIPIP system cannot be reconciled with the supposition that only one of the above diamine solvated complexes (eg. Pi S) is active in polymerization 162). This is probably true of other diene polymerizations and other diamines. The observations suggest a more complex system than described above for styrene polymerization in presence of TMEDA, This result is clearly connected with the increased association number of uncomplexed diene living ends which permits a greater variety of complexes to be formed. 

Multi-State Models. In studies of copolymerization kinetics and polymer microstructure, the use of reaction probability models can provide a convenient framework whereby the experimental data can be organized and interpreted, and can also give insight on reaction mechanisms. (1.,2) The models, however, only apply to polymers containing one polymer component. For polymers with mixtures of different components, the one-state simple models cannot be used directly. Generally multi-state models(11) are needed, viz. 

Controlling polymer microstructure through novel catalysis and chemistry... 

In the past three decades, industrial polymerization research and development aimed at controlling average polymer properties such as molecular weight averages, melt flow index and copolymer composition. These properties were modeled using either first principle models or empirical models represented by differential equations or statistical model equations. However, recent advances in polymerization chemistry, polymerization catalysis, polymer characterization techniques, and computational tools are making the molecular level design and control of polymer microstructure a reality. 

Advanced computational models are also developed to understand the formation of polymer microstructure and polymer morphology. Nonuniform compositional distribution in olefin copolymers can affect the chain solubility of highly crystalline polymers. When such compositional nonuniformity is present, hydrodynamic volume distribution measured by size exclusion chromatography does not match the exact copolymer molecular weight distribution. Therefore, it is necessary to calculate the hydrodynamic volume distribution from a copolymer kinetic model and to relate it to the copolymer molecular weight distribution. The finite molecular weight moment techniques that were developed for free radical homo- and co-polymerization processes can be used for such calculations [1,14,15]. 

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