Lattice-controlled polymerization

Eq. 2-248) [Braun and Wegner, 1983 Hasegawa et al., 1988, 1998]. This polymerization is a solid-state reaction involving irradiation of crystalline monomer with ultraviolet or ionizing radiation. The reaction is a topochemical or lattice-controlled polymerization in which reaction proceeds either inside the monomer crystal or at defect sites where the product structure and symmetry are controlled by the packing of monomer in the lattice or at defect sites, respectively. 

Homochiral Polymers via 2-D Self-Assembly and Lattice-Controlled Polymerization... 

According to the packing arrangement shown in Fig. 16c, it was anticipated that a lattice-controlled polymerization within such crystallites, in... 

Reactivity within (DL)-PheNCA crystals provides a number of simple ways to de-symmetrize the racemic mixtures of the homochiral oligopeptides. For example, L-2-(thienyl)-alanineNCA (ThieNCA) molecules have been shown to enantioselectively occupy the L-sites in the DL-PheNCA host crystals. Lattice-controlled polymerization of such D-Phe/(L-Phe L-Thie)-NCA mixed crystals yields libraries of non-racemic oligopeptides of ho-... 

This article describes the solid state polymerization of 1,i-disubstituted butadiene derivatives in perovskite-type layer structures, in layered structures of organic ammonium halide salts, and in lipid layer structures. Recent investigations by spectroscopic methods and x-ray structure analyses are described. The studies clearly indicate that the photolysis in the crystalline state leads to the formation of 1,i-trans-polymers exclusively. Crystal structure analyses of monomeric and polymeric layer perovskites demonstrate that upon y-irradiation a stereoregular polymer is obtained in a lattice controlled polymerization. 

Moreover, it will be shown by x-ray structure analyses of layer perovskites in the monomeric and polymeric states that y-irradiation leads to the formation of a stereoregular polymer in a lattice controlled polymerization. The properties of the polymers will be discussed briefly. 

Only recently, examples of a lattice controlled polymerization of butadiene deri-vatieves have been reported 24,25.167-171) yy y-irradiation of butadienes crystallized in perovskitetype layer structures yielded erythro-diisotactic 1,4-trans-polymers Furthermore, crystalline 1,4-trans-polymers could be obtained upon UV-or y-irradiation of native halide salts of unsaturated primary amines and long chain butadienes in lipid layer structures... 

In such reactions, the only chiral influence utilized by the asymmetric synthesis is the enantiomorphic crystal structure of one of the reactants. Lahav et al [210, 211] studied a number of divinyl monomers known to undergo lattice-controlled polymerization they are unsymmetrically substitued and contain chiral handles which favor crystallization in asymmetric structures. Unambiguous OA dimer and oligomer were obtained by UV irradiation of a highly crystalline sample. 

Another family of diolefins in which a similar reaction was observed is that of phenylene diacrylic acid 2 and its derivatives. These also undergo lattice-controlled polymerization, and the very close relationship between the packing of the diacrylic acids, cinnamic acid, and DSP is shown in Figure 6.1. 

The solid-state polymerization of diacetylenes is an example of a lattice-controlled solid-state reaction. Polydiacetylenes are synthesized via a 1,4-addition reaction of monomer crystals of the form R-C=C-CeC-R. The polymer backbone has a planar, fully conjugated structure. The electronic structure is essentially one dimensional with a lowest-energy optical transition of typically 16 000 cm-l. The polydiacetylenes are unique among organic polymers in that they may be obtained as large-dimension single crystals. 

In contrast, due to the typical temperature effect on the lattice-controlled process of a four-center photopolymerization, in the case of a few diolefin crystals such as m-PDA Me (m.p. 138 °C), only the amorphous oligomer is produced at all the temperature ranges attempted. In the polymerization of m-PDA Me higher temperatures favor chain growth. This behavior is reasonably well explained by lattice-controlled dimerization followed by random cyclobutane formation yielding the oligomer through the thermal diffusion process (Sect. IV.b.)22. ... 

PDA Me, CVCC Me and DSP (y) in Table 4 demonstrate that the polymerization proceeds by a diffusionless crystal-lattice controlled mechanism31. ... 

In order to visualize the details of the elementary processes in polymerization, the monomer crystal-lattice control of the three processes - initiation (i), propagation (ii), and crystallization of polymer (iii) - has been examined on the basis of structural charac-tristics of the resultant polymer44. ... 

Good coincidence of the X-ray patterns of these two kinds of oligomers suggests that the thermal chain scission in as-polymerized poly-DSP crystals does not proceed randomly at the position of cyclobutane ring in the molecular chain but is somewhat favored on the position of cyclobutane ring in the middle of the chain655. Thus, the oligomer crystal is preferentially accumulated in thermal depolymerization under the polymer crystal-lattice control. This abnormal chain scission is most plausibly explained when the... 

At present there is considerable interest in studying various topics relating to or deriving from solid-state polymerization. This has come about because of interesting and potentially useful properties of several polymers formed by lattice-controlled processes and because of the natural desire to increase the number of systems available for additional study. The experimental results alluded to have been achieved in the last several years, and it is now appropriate to take stock of these activities to understand how and why they have come to their present state and also to see how they might be given greater breadth and depth. 

Recently, the term design of a solid-state polymerization was introduced with a view toward discovery and development of new lattice-controlled processes (. The term implies not easily separedile crystallographic and mechanistic issues, and it was suggested 7) that mechanistic aspects of initiation and propagation may hold the key to progress along these lines. 

While some of the above discussion is in the general reedm of prognostication, some mote specific comments are appropriate. It is appeuent that em increase in both the number and types of solid-state polymerization is a desirable research objective. Here, the major initial burden lies with the chemist to design (, new reactive molecular structure and appropriately oriented monomer crystal structures. Successful development of new lattice-controlled processes resulting in the availability of well-defined fully ordered mticromolecules will readily attract the more physically and theoreticedly oriented research communities. The PDA and poly (sulfur nitride) cases bear strong witness to this point. 

Our investigations show that 1,4-disubsituted butadiene derivatives react in layered structures under exclusive formation of 1,i-trans-polymers. A stereoregular polymer is obtained. The structure analyses of the monomer and polymer crystals of 1 show that a lattice-controlled reaction takes place. It is certainly worthwhile studying the course of the reaction more in detail, and to compare the reaction mechanism and kinetics with those of other lattice-controlled reactions, as, for example, the polymerization reactions of diolefin 12Z) and butadiyne derivatives (23). 

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. 

In this paper, we show that phonon spectra can conveniently be used to understand the mechanism of the lattice control of the reaction. Phonon spectral study as a function of the reaction can be used to identify any lattice intermediates as well as deduce the mechanism of polymerization. Furthermore, it can also be used to derive information on the extent of order in the polymer product. 

Yesinowski, J.P. Eckert, H. Sandman, D.J. Velazquez, C.S. In "Solid State Polymerization and the Structure and Properties of Polymers Produced by Lattice-Controlled Processes Sandman, DJ., Ed. ACS SYMPOSIUM SERIES, to be published. 

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