Novel polymerization approaches

In the last 50 years, scientists have developed novel polymerization approaches, leading to new polymeric materials and applications, with the pace of new discoveries growing. This chapter provides an overview of this body of research, focusing on reactions involving covalent modification of double bonds to prepare monomers (particularly on the formation of polyols for employment as monomers for polyurethane synthesis), direct polymerization reactions between polyunsaturated acyl groups (eg, Diels-Alder, free radical, metathesis. 

The silanization reaction has been used for some time to alter the wetting characteristics of glass, metal oxides, and metals [44]. While it is known that trichlorosilanes polymerize in solution, only very recent work has elucidated the mechanism for surface reaction. A novel FTIR approach allowed Tripp and Hair to prove that octadecyl trichlorosilane (OTS) does not react with dry silica. 

Polymer libraries have recently been the focus of several publications with the aim either to discover novel polymeric materials for a specific application (primary libraries) or to rapidly optimize the properties of known polymers (focused libraries). All the major areas where successful combinatorial approaches to polymer libraries have been reported are covered in the following sections with the help of a specific, recent example and up-to-date referencing. Several other papers dealing with polymer combinatorial libraries can be consulted by the interested reader (80-89). 

An interesting new approach in this area has been reported with the synthesis of novel polymeric zirconocene-silsesquioxanes 134. " The condensation of zirconocene derivatives with polyhedral silsesquioxanes led to... 

In a different approach, microwave-mediated oxazole synthesis utilizing ji-ketoesters bound to a novel polymeric resin has been described [57]. The desired polymer support was prepared by transesterification reactions between tert-butyl j5-ketoesters and hydroxybutyl functionalized Janda/el resin, and subsequent standard diazo transfer. The resulting a-diazo j5-ketoesters have been used for synthesis of an array of oxazoles (Scheme 16.34). Because of the thermal sensitivity of the Burgess reagent used, the temperature was kept rather low, but irradiation for 15 min at 100 °C furnished satisfactory results [57]. Cleavage from the solid support was achieved by diversity-introducing amidation this led to the corresponding oxazole amides in reasonable yields. 

On the basis of existing knowledge, novel quantitative approaches for the analysis of tetracyclines should involve extraction under mild acidic conditions, incorporate metalchelating agents, and investigate polymeric SPE sorbents. In addition, they should be able to detect and quantify OTC, TC, CTC, DC, and their associated 4-epimers at concentrations that are fit for their intended purpose. If confirmation is required, LC-MS/MS is recommended for its selectivity. 

An interesting new approach in this area has been reported with the synthesis of novel polymeric zirconocene-silsesquioxanes (4.15) with R=cyclohexyl [42, 43]. The condensation of zirconocene derivatives with polyhedral silsesquioxanes led to amorphous polymers in high yields ( 90%) that were characterized by NMR spectroscopy and elemental analysis. These high molecular weight (M =14,000) materials exhibited high thermal stability (to ca. 475-515 °C) and, surprisingly, 4.15 a was found to be stable to both air and hydrolysis. 

The progress of chemistry, associated with the industrial revolution, created a new scope for the preparation of novel polymeric materials based on renewable resources, first through the chemical modification of natural polymers from the mid-nineteenth century, which gave rise to the first commercial thermoplastic materials, like cellulose acetate and nitrate and the first elastomers, through the vulcanization of natural rubber. Later, these processes were complemented by approaches based on the controlled polymerization of a variety of natural monomers and oligomers, including terpenes, polyphenols and rosins. A further development called upon chemical technologies which transformed renewable resources to produce novel monomeric species like furfuryl alcohol. 

In this chapter, we describe few examples of gas phase and intracluster oligomerization reactions for the study of the early stages of polymerization and present methods for the synthesis of polymeric materials containing ultrafine and nanoparticles. We also discuss several approaches and opportunities to study gas phase polymerization and synthesize novel polymeric materials in microgravity. 

In this chapter, we have described a novel design approach to correct flow nonuniformities caused by four types of production variations in a linearly tapered coat-hanger die. The theoretical approach is based on the onedimensional lubrication approximation and can be used to predict the taper function of an adjustable choker bar. Once a choker bar is constructed based on the prediction of the mathematical model, the flow nonuniformities can be properly eliminated by inserting this bar into the die. A choker bar can be tapered in different ways as indicated in Fig. 3. The shape displayed in Fig. 3a may be easier to machine and was selected for illustration. The four production variations we have considered include (i) enlarging the manifold, (ii) including the fluid inertial terms, (iii) varying the viscosity of the polymeric liquids, and (iv) narrowing the liquid film width to meet production requirements. All these four production variations can be properly handled, but if the fluid inertia becomes dominant, or the Reynolds number is not small, the present method may not be applicable. 

In a precursor-polymer synthetic approach [288], amphiphiles which formed charged complexes with precursor polymers of poly(p-phenylene vinylene) (P(PV)) and poly(thienylene vinylene) (P(TV)) were spread onto solutions of these precursor polymers. This unique complex is then transferred to an appropriate substrate using standard LB techniques, and then converted to P(PV) or P(TV) via heat treatment. In a similar but rather novel, in-situ polymerization approach from the Rubner group [289], LB films of ferric stearate are exposed sequentially to HCl vapor (generating FeCls oxidant) and pyrrole monomer, yielding conductive LB P(Py) films. 

H.C. Kang, K.M. Huh, Y.H. Bae, Polymeric nucleic acid carrier Current issues and novel design approaches, J. Control. Release 164 (2012) 256-264. 

Polymerization ofiVIasked Disilenes. A novel approach, namely, the anionic polymerization of masked disilenes, has been used to synthesize a number of poly(dialkylsilanes) as well as the first dialkylamino substituted polysilanes (eq. 13) (111,112). The route is capable of providing monodisperse polymers with relatively high molecular weight M = lO" — 10 ), and holds promise of being a good method for the synthesis of alternating and block copolymers. 

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