Solid-state polymerization dynamics

In some special cases, however, both the polymerization and the side group reorientation are single phase processes. They are of special interest for understanding the dynamics and side group mobility in the solid-state polymerization of diacetylenes. 

Previously, we found that the di(4-alkoxybenzyl) esters of ( , )- and (Z,Z)-muconic acids have different geometric structures, but the obtained polymers have completely identical chemical structures with the same tacticity (Scheme 24.5) [82-84], We investigated the molecular dynamics during the polymerization of (E,E)-4MeO, (Z,Z)-4MeO, monitored by in situ single and powder X-ray diffraction experiments in order to discuss a reaction mechanism for the solid-state polymerization... 

This paper presents studies of solid state polymerization aimed towards formulating a dynamic model of reactivity in the condensed phase. Phonon spectroscopy is successfully used to elucidate the mechanism of lattice control of the reaction. Novel concepts of phonon-assisted thermal and photochemical reactions are introduced, supported by experimental data. Non-linear laser spectroscopy is used to find the importance of biexcitonic processes in photopolymerization. Also, spectroscopic studies of reactions in Langmuir-Blodgett films and at gas-solid interface which produce ordered polymers are presented. 

Phonon spectroscopy has been found to be a powerful method to Investigate the reaction dynamics In solid state. Also, non-llnear laser spectroscopic study has been used to probe the dynamics of photochemical reactions. Future directions are clearly a more quantitative and theoretical formulation of the Importance of energy state dynamics In determining reactivity In the condensed phase. Non-llnear spectroscopy as well as time-resolved X-ray crystallography using synchrotron radiation can be expected to provide valuable approaches for future development of a dynamic model of solid state polymerization. 

Dynamic mechanical and NMR investigations of crystals grown from dilute solutions for polymers other than linear polyethylene have been much less extensive. Studies have been reported for the linear polymers polyoxy methylene (3, 40, 94), poly (ethylene oxide) (3, 78), and nylon 6 (42), and the branched polymers polypropylene (40), poly-l-butene (19, 95), poly(4-methyl-l-pentene) (33), poly (vinyl alcohol) (78), and branched polyethylene (78). In addition, dielectric loss measurements have been made on crystal aggregates of poly (ethylene oxide) (23), poly (vinyl alcohol) (68), and polyoxymethylene (3) and mechanical loss measurements have been carried out on polyoxymethylene formed by solid state polymerization (94). 

Table 7.6 Dynamic model of a nylon 6,6 solid-state polymerization reactor...

Solid-state polymerization of crystalline monomer without any intermediate loss of order. The topotactic oligomers have been produced, but the order is lost as the polymerization progresses beyond a low degree of polymerization. Test equipment used for determining the dynamic mechanical properties of plastics. 

In order to illustrate the use of the iGLE and WiGLE models for polymerization reactions, we have studied several phenomenological forms of the polymer PMF of Fig. 5. In the studies to date, the nonstationary frictions have always included the form of Eq. (28) and as such are apphcable only to dense polymerizations. This class would certainly include solid-state polymerization (SSP) as long as none of the other quenching mechanisms discussed above were also operative, and the assumptions of the separation of time scales in the environmental motion are satisfied. In SSP, the heterogeneity in the environment would further require the use of the WiGLE dynamics with the possible inclusion of a time dependence in the w parameter. 

The aim of this Chapter is to review our spectroscopic work towards the analysis of both, the electronic structures and the dynamics of the intermediate reaction products (Fig. 9.2), during the photopolymerization, i. e. after the excitation of the solid state reaction by light. For the entirely thermally activated solid state polymerization detailed spectroscopy of the intermediate states turned out to be difficult or not very efficient. One exception was the identification of carbenes as reactive species during the thermal solid state polymerization of TS6 (Fig. 9.8). 

With further understanding how molecular rotors interact with their environment and with application-specific chemical modifications, a more widespread use of molecular rotors in biological and chemical studies can be expected. Ratiometric dyes and lifetime imaging will enable accurate viscosity measurements in cells where concentration gradients exist. The examination of polymerization dynamics benefits from the use of molecular rotors because of their real-time response rates. Presently, the reaction may force the reporters into specific areas of the polymer matrix, for example, into water pockets, but targeted molecular rotors that integrate with the matrix could prevent this behavior. With their relationship to free volume, the field of fluid dynamics can benefit from molecular rotors, because the applicability of viscosity models (DSE, Gierer-Wirtz, free volume, and WLF models) can be elucidated. Lastly, an important field of development is the surface-immobilization of molecular rotors, which promises new solid-state sensors for microviscosity [145]. 

Oligomerization of nucleobases can be advantageous to reinforce the H-bonding supramolecular motifs when supramacromolecular polymers are desired. Moreover the different interconverting outputs that may form by oligomerization define a dynamic polyfunctional diversity which may be extracted selectively under the intrinsic stability of the system or by interaction with external factors by polymerization in the solid state. 

Nuclear magnetic resonance (NMR) spectroscopy is a most effective and significant method for observing the structure and dynamics of polymer chains both in solution and in the solid state [1]. Undoubtedly the widest application of NMR spectroscopy is in the field of structure determination. The identification of certain atoms or groups in a molecule as well as their position relative to each other can be obtained by one-, two-, and three-dimensional NMR. Of importance to polymerization of vinyl monomers is the orientation of each vinyl monomer unit to the growing chain tacticity. The time scale involved in NMR measurements makes it possible to study certain rate processes, including chemical reaction rates. Other applications are isomerism, internal relaxation, conformational analysis, and tautomerism. 

Dynamic mechanical analysis methods are frequently used to investigate polymerization and curing processes in reactive systems. These methods allow us to obtain both relative and absolute rheological characteristics of a material. Measurements can be made in both the fluid and solid states without affecting the inherent structure of the polymerizing system. 

Dynamic mechanical measurements describe both the liquid and solid states and are the best methods for following the physical changes occurring during the polymerization in the whole conversion range. The main observations are... 

L. Monnerie in Static and Dynamic Properties of the Polymeric Solid-State, Eds., R.A. Pethrick and R.W. Richards, D. Reidel Publishing, Dordrecht, The Netherlands, 1982. 

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