Post-polymerisation

Bead Processes. These processes have generally replaced the above techniques. The styrene is polymerised by bead (suspension) polymerisation techniques. The blowing agent, typically 6% of low boiling petroleum ether fraction such as n-pentane, may be incorporated before polymerisation or used to impregnate the bead under heat and pressure in a post-polymerisation operation. 

Table 6. Post-polymerisation of y-benzyl-i.-glutamate NCA. The reaction was initiated by sodium methoxide in dioxane solution at constant monomer concentration...

This result, and the occurrence of post-polymerisation, are highly significant. They indicate ... 

The effect of reactive plasma and its distance form the PE film surface has also been studied in detail [138]. The surface of polyethylene films was modified with various water-soluble polymers [(poly[2-(methacryloy-loxy)ethyl phosphorylcholine] (PMPC), poly[2-(glucosyloxy)ethyl methacrylate] (PGEMA), poly(N-isopropylacrylamide) (PNIPAAm) and poly[N-(2-hy-droxypropyl) methacrylamide] (PHPMA)] using Ar plasma-post polymerisation technique [139]. Here, the reactive sites were generated on the PE surface under the influence of argon plasma. These reactive sites on the surface were then utilised to covalently anchor the functional monomers as shown in Scheme 11. 

Davankov and his co-workers [55, 56] first discovered these remarkable resins. They are prepared either by chemically crosslinking linear polystyrene in a post-polymerisation treatment, or similarly post-treating lightly crosslinked (with —0.3-2% divinylbenzene) polystyrene resins. Reagent quantities are chosen to allow exhaustive Friedal-Crafts alkylation of aromatic... 

In the past post polymerisation processing of (inherently) electrically conductive polymers (ICP) has not been broadly focused on. 

Based on more than 15 years of research work in this area in our laboratories, the author reviews post polymerisation processing results. Recent findings are presented and described in the context of a new materials science concept for ICE... 

The kinetic equations obtained for stationary and non-stationary (so-called post polymerisation) processes [25, 26] qualitatively explain all the main features of block 3-dimensional polymerisation at high degrees of conversion. This feature has also been quantitatively proven on a wide range of experimental materials connected with the kinetics of photoinitiated polymerisation of dimethacrylates. This allows for the first time a numeric estimate of the rate constants for linear chain termination to be made [29]. 

It is the aim of this chapter to give an overview on both chemical and electrochemical techniques for producing metallic-particle-based CP nanocomposite materials and to outline the progress made in this field. The various synthetic approaches are organized in such a way as to present first those involving metal particle deposition in the course of polymerization, and subsequently post-polymerisation procedures that involve chemical, electrochemical, or adsorption processes (Figure 7.1). Well-established approaches, along with some newly developed techniques will be discussed, with special emphasis on those that are still underdeveloped. Synthesis of metal oxide particle-based CP composites (see e.g. [8]), as well as modification of CPs with transition-metal complexes (see e.g. [5]) remain outside the scope of this chapter. 

The presence of bulky halogens in the 3,3 -positions would disfavor p-coupling, which will result in diminished conductivities, d. The resulting polymers having reactive pendant halogens would readily lend themselves to further functionalisation/modification in the post-polymerisation stage. 

In order to defend its share of the pipe market in the advanced economies of Western Europe, uPVC has had to offer the possibility of improved mechanical performance [10]. Improvement of low temperature toughness was achieved by alloying it with other polymers. Greater pressure containment strength was achieved by molecular orientation in the pipe wall and higher temperature rating was achieved by post-polymerisation chlorination. 

A variation on PVC that is important for some pipe applications is Chlorinated PVC (CPVC). This is manufactured by chlorination at a post-polymerisation stage. The modified polymer which carries additional chlorine atoms has a stiffer polymer chain resulting in better high temperature performance than PVC. CPVC has therefore been used for piping hot water and industrial chemicals where it continues to be used in competition with PP and crosslinked PE. The mechanical properties and chemical resistance characteristics of CPVC are similar to PVC. 

Another significant application of the ADMET polymerisation relates to the preparation of star-shaped polymers, which are branched macromolecules in which several linear polymer chains are attached to a unique branching point or core [48]. Montero de Espinosa, Winkler and Meier [49] described an ADMET approach to obtain those architectures (three- and four-arm) using small tri-acrylates and tetra-acrylates. More recently, Unverferth and Meier [50] reported the synthesis of well-defined star-shaped polymers via a head-to-tail ADMET polymerisation whereby di(trimethylolpropane)tetra-acrylate (four-arm) and dipentaerythritol hexa-acrylate (six-arm) served as core units, and fatty acid-derived 10-undecenyl acrylate as asymmetric a,(0-diene monomers. In this case, star-shaped polymers containing arms of 10 or 20 monomer units with an a,(0-unsaturated ester backbone and their subsequent post-polymerisation via a base-catalysed Thia-Michael addition were prepared. 

Post-polymerisation modifications of polymer structures based on the thiol-ene reaction are important tools in macromolecular science because several thiol compounds bearing diverse functional groups can be introduced easily onto a polymer chain that bears non-activated mono-substituted double bonds as functional groups... 

Cadiz and co-workers [46] prepared telechelic polyester diols through two subsequent thiol-ene reactions. That is, a step growth polymerisation using allyl-lO-undecenoate and 3,6-dioxa-l,8-octanedithiol, followed by end-group post-polymerisation modification with 2-mercaptoethanol. Telechelics based on divinyl monomers are interesting materials with potential applications in the tailoring of polymer structures and properties. 

Scheme 6.16 Post-polymerisation modification of DecEnOx-derived polymers [47]...

The mechanisms involved in monomer removal by post polymerisation were studied. Three redox initiator systans which generate radicals with different hydrophobidties were investigated tert-butyl hydroperoxide, hydrogen peroxide and potassium persulphate. Ascorbic acid was used as a reductant in all cases. The efficiency of these initiator systems for the removal of residual monomers from commercial latexes was studied. The examples exauuued were removal of unreacted vinyl acetate from a vinyl acetate/butyl aerylate/acrylie acid latex, methyl methacrylate from a methyl aaylate, butyl aaylate/acryhc acid latex and butyl acrylate from a butyl aaylate/styrene/ acrylic acid latex. Efficieucy of monomer ranoval by post polymerisation increased with the hydrophobidty of the radical formed from the initiator system and this was independent of the water solubihty of the residual monomer. Reasons for the observations were discussed. 35 refs. 

The post-polymerisation of vinyl acetate (Vac)-containing latexes with tert-butyl hydroperoxide TBH/ascorbic acid (AsA) as a redox initiation system is investigated. Volatile organic compounds (VOCs) such as acetone and tert-butyl alcohol are produced in this process. The influence of the TBH/AsA ratio, initiator concentration, reaction temperature and feeding time on the reduction of residual VAc and VOC formation during the post-polymerisation is investigated. A total reduction of residual VAc monomer is achieved, with the formation of VOCs kept within acceptable limits. 11 refs. 

The polyamide granules are fed into a mixer (extmder) where they are melted. In some processes, the polymer melt comes directly from pol5merisation (direct-spinning) or, in the case of polyamide 66, from post-polymerisation. 

C-NMR spectra of the labelled networks were obtained by direct polarisation, liquid-state method with fully CDCl3-swollen samples, and by the solid-state, CP-MAS with solid samples. By both methods, the 1 % crosslinked samples prepared at 70 "C and at 95 °C showed a peak at 137 ppm due to the labelled carbon of unpolymerised vinyl groups. The 137 ppm signal was not seen after further polymerisation of the 1 % crosslinked sample at 135-155 C. Polystyrenes prepared with 10% and 20% of the labelled DVB by the same procedures showed residual vinyl groups before and after the 135-155 °C post-polymerisation. With the 10% and 20% crosslinked samples, only CP-MAS spectra gave peaks of labelled carbon narrow enough to analyse. 

---