In situ copolymerization

An alternative route for the preparation of styrenic macromonomers is the reaction of living chains with 4-(chlorodimethylsilyl)styrene (CDMSS) [192]. The key parameter for the successful synthesis of the macromonomers is the faster reaction of the living anionic chain with the chlorosilane group rather than with the double bond of the CDMSS. Anionic in situ copolymerization of the above macromonomers (without isolation) with conventional monomers leads, under appropriate conditions, to well-defined comb-like chains with a variety of structures. 

Epoxy resins have been toughened by in situ copolymerization of microgels consisting of unsaturated polyesters and bifunctional comonomers [382,383]. 

Another way to improve the performance of open-tubular columns was suggested by Sawada and Jinno [83]. They first vinylized the inner surface of a 25 pm i.d. capillary and then performed in situ copolymerization of f-butylacryl-amide and 2-acrylamido-2-methyl-l-propanesulfonic acid (AMPS) to create a layer of polymeric stationary phase. This process does not currently allow good control over the homogeneity of the layer and the column efficiencies achieved in CEC separations of hydrocarbons were relatively low. These authors also recently thoroughly reviewed all the aspects of the open tubular CEC technologies [84]. 

Moreover, in-situ copolymerization approaches of polymerizable chiral cin-chonan carbamate selectors have also been shown to be viable straightforward routes to enantioselective separation media. In one approach, polymethacrylate-type monoliths have been fabricated by copolymerization of functional monomers and crosslinker in presence of porogenic solvents [80-85]. They have been utilized mainly for CEC (and will be described in detail later) while they turned out to be less suitable for HPLC application because of a low crosslinking degree. 

Monolithic columns with the chiral anion exchange-type selectors incorporated into the polymer matrix obtained through in situ copolymerization process of a chiral monomer (in situ approach) [80-83,85] or attached to the surface of a reactive monolith in a subsequent derivatization step (postmodification strategy) [84], both turned out to be viable routes to enantioselective macroporous monolithic columns devoid of the limitations of packed columns mentioned earlier. 

In a related study this group also demonstrated the use of non-volatile solvents in CEC-MS without compromising the quality of spectra that has also been demonstrated using polymer-based monolithic column prepared by in situ copolymerization of butyl methacrylate with sulfonic acid functionalities. 

Co(acac)3 is frequently used as a probe for enantioseparation efficiency of col-umns " . A monolytic capillary silica gel column was functionalized with methacrylate residues in two steps, as shown in equation and then it was impregnated with cellulose or amylose (51a, b) which was modified so that 30% of the R groups were the methacrylate group 52 and the rest was identical to R (53). For further stability of the column, the polymeric modifier was immobilized on the silica gel by in situ copolymerization with an olefinic monomer such as 2,3-dimethylbutadiene. Only the column containing cellulose modified as in 51a was able to separate the Co(acac)3 racemic mixture, whereas neither cellulose nor amylose modified as in 51b did, although they were successful in resolving other racemic mixtures ° °. ... 

The long-term effectiveness of TBTMA as a biocide has been confirmed (23). The deterioration of southern pine wood specimens impregnated with TBTMA has been compared with specimens that were treated with pentachlorophenol methacrylate (PGPMA) or pen-tabromophenol methacrylate (PGBMA). The three esters were incorporated as the copolymer by in situ copolymerization with methyl methacrylate (MMA) at different molar ratios of the comonomers. 

Radical-catalyzed graft copolymerization is generally accompanied by crosslinking or scission (or both) of the substrate polymer. Gel permeation chromatographic analysis of polymer carboxylated by the in situ copolymerization of styrene and maleic anhydride without a radical catalyst shows that the molecular size distribution of the carboxylated... 

Pore-filling MIP composite membranes had been first prepared by Dzgoev and Haupt [100]. They casted the reaction mixture into the pores of a symmetric microfiltration membrane from polypropylene (cutoff pore size 0.2 pm) and performed a cross -linking copolymerization of a functional polyacrylate for imprinting protected tyrosine. Hattori et al. [101] had used a commercial cellulosic dialysis membrane (Cuprophan) as matrix and applied a two-step grafting procedure by, (i) activation of the cellulose by reaction with 3-methacryloxypropyl trimethoxysilane from toluene in order to introduce polymerizable groups into the outer surface layer, (ii) UV-initiation of an in situ copolymerization of a typical reaction mixture (MAA/EDMA, AIBN) for imprinting theophylline. 

Scheme 56 Tandem multiwalled carbon nanotubes (MWCNTs) coating through in situ copolymerization catalysis of ethylene with Zr/Co or Ti/Co systems...

Zhang, Z., Guo, C.-Y., Cui, N., Ke, Y, and Hu, Y. 2004. Preparation of linear low density polyethylene by in situ copolymerization of ethylene with Zr supported on montmorillonite/ Fe/methylaluminoxane catalyst system. Journal of Applied Polymer Science 94 1690-1696. 

Figure 28 Preparation of the photonic structural sensors from colloidal crystalline arrays (CCAs) is performed by in situ copolymerization of the polymerizable receptor to yield polymerized colloidal crystalline arrays (PCCAs). A receptor-analyte recognition process can affect the changes in the CCA periodicity, and, following Bragg s law, the wavelengths of diffracted and transmitted light, which serve as a signal for the sensing event.

The ability to incorporate long-chain branches appears reasonably common among metallocene catalysts. Experimental results for LCB formation with both CGC and conventional metallocene-catalyzed polymerizations are in line with an in situ copolymerization mechanism. For copolymerization of vinyl-terminated polyethylene molecules to occur, the first requirement is the presence of termination mechanisms producing vinyl-terminated macromonomers. Secondly, the catalyst must able to incorporate these macromonomers into a growing chain. Macromers probably do not move from one active site to another, but instead insertion of macromer to another chain takes place at same site where it was formed in a intramolecular incorporation manner. 

Elimination of a polymerizable fragment and its incorporation in the polymeric chain (viz., in situ copolymerization with the monomer and ligand) can also lead to unit variability. In addition, radical fragments can initiate polymerization, recombine, and abstract a hydrogen atom from coordinated ligand. 

PFT usually involves in situ copolymerization of olefins catalyzed directly from nanotubes pietreated by a methylalumi- noxane (MAO) or highly active metallocene-based complexes (e.g., Cp ZrCl ). This approach destroys nanotube bundles and results in homogeneously coated CNTs [22]. 

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