Bis-unsaturated monomer

The monocarbanionic precursor chains can also serve as a efficient initiator for the polymerization of a small amount of a bis-unsaturated monomer, such as divinylbenzene (DVB) or ethylene glycol dimethacrylate (EGDMA) (Scheme 4). 

The average number of branches per star molecule [49] is influenced by several factors, the most important of which are the overall concentration of the reaction medium and the proportion of bis-unsaturated monomer. The proportion of bis-unsaturated monomer is expressed as the mole ratio of monomer to the active sites, [DVB]/[LE]. Depending on the average length of the precursor chains, a given [DVB]/[LE] mole ratio results in different weight-percents in the cores of the star molecules. 

The anionic arm-first methods can also be applied to the synthesis of star block copolymers [59]. The procedure is identical except that living diblock copolymers (arising from sequential copolymerization of two appropriate monomers, added in the order of increasing nucleophilicity) are used as living precursor chains. The active sites subsequently initiate the polymerization of a small amount of a bis-unsaturated monomer (DVB in most cases) to generate the cores. If polystyrene and polyisoprene (or polybutadiene) are selected, the resulting star block copol)miers behave as thermoplastic elastomers because of their different glass transition temperatures. 

In general, star polymers can be synthesized by two different approaches, known as arm-first and core-first methods [23]. The arm-first method consists of either terminating the living chain end by plurifunctional electrophiles or reinitiation using bis unsaturated monomers. In the core-first method, a plurifunctional initiator core is first synthesized by reaction of an initiator with a bis-unsaturated monomer (e.g., reaction of -BuLi with divinyl-benzne). The plurifunctional initiator core is used to initiate fiirther polymerization. The synthetic advantages and drawbacks of the two methods are summarized in Table 4. 

The schematic representation of (AB) star and A B star copolymers are shown in Fig ure 21. Generally, the A B star copolymers were prepared by using a three-step anionic [56,57] or cationic [58] process. A living precursor polymer was made first, and used to initiate the polymerization of a small amount of a bis-unsaturated monomer, so as to build star molecules. Each of the resulting cores was linked to precursor chains that had contributed to its initiation. This living polymer was used subsequently to initiate the polymerization of another monomer, implying that new branches were growing out from the core. 

On the other hand, the (AB) star copolymers were prepared by the condensation of AB diblock anions using chlorosilane compound [59]. This star copolymer could also be synthesized by crosslinking diblock monocarbanionic [60,61] or monocarbocationic chains [62,63] with bis-unsaturated monomers. 

By anionic block copolymerization of two monomers, thesecond being bi-unsaturated... 

As the unsaturated monomers in the BPA/DC systems, allyl ethers of bisphenols, e.g. bis(4-allyloxyphenyl)sulfone, were used. Tg = 260 °C was reached [130]. 

Unsaturated monomers have been adsorbed on to fillers and then polymerised to give encapsulated products. The modulus of the polymer could be modified by selecting the monomer [40]. Acrylic acid-vinyl chloride (1 99) has been polymerised on to calcium carbonate [41] reports of the use of 3,5-triacryloxyhexahydro-S-triazine [42], bis-phenol A and epichlorohydrin [43], methyl methacrylate [44], and acrylic acid [45] have also been published. 

The use of solid-liquid phase transfer catalysis in the conjunction with bis(carbonylimidazolides) (i) bis(p-nitrophenylcarbonates) 10) as developed by Fre-chet for the synthesis of novel tertiary copolycarbonates. The instability of tertiary chloroformates renders tertiary polycarbonates inaccessible through conventional chloroformate monomers or intermediates. The bis(carbonylmiidazoiide) monomer was shown to polymerize with both tertiary (3) and secondary alcohols (lljy demonstrating the utility of the method in forming polycarbonates fi-om less reactive steri-cally hindered monomers. Most of the examples reported involved benzene dimethanol derivatives, or 1,4-butynediol, indicating that an adjacent site of unsaturation may activate the alcohol in the solid-liquid phase transfer reaction scheme. 

Binary free-radical copolymerizations of organotin derivatives of unsaturated acids (tri-n-butylstannyl methacrylate, bis-triethylstannyl maleate (TESM) and P-phenyl-tri-n-butylstannyl methacrylate (PBSM)) with certain vinyl monomers such as styrene (St) 87) and vinyl chloride (VC) have been studied 24,25,92). 

Fig. 3. (Top left) Chemical methods used to depolymerize the polyesters. (Top right) Thin-layer and gas-liquid chromatograms (as trimethylsilyl derivatives) of the monomer mixture obtained from the cutin of peach fruits by LiAlD4 treatment. In the thin-layer chromatogram the five major spots are, from the bottom, C18 tetraol, C16 triol, and C18 triol (unresolved), diols, and primary alcohol. Nx = C16 alcohol N2= C18 alcohol Mj = C16 diol M2 = C18 diol D = C16 triol D2 and D3 = unsaturated and saturated C18 triol, respectively, T4 and T2, unsaturated and saturated C18 tetraol, respectively. (Bottom) Mass spectrum of component D3 in the gas chromatogram. BSA = bis-N,O-trimethylsilyl acetamide...

Bisbenzocyclobutenes readily react with molecules which contain sites of reactive unsaturation such as bismaleimides [10,13, 31, 32]. This is in essence, a novel type of Diels-Alder polymerization in which the bis-diene is latently embodied within two benzocyclobutene moieties. The properties of these polymers depends strongly on the mole ratio of the monomers and when it is equimolar, can result in some exceptionally tough high Tg resins [33, 34]. 

The polymerization of bis( 1,1-diphenyl vinyl) monomers 59a-d gave polymers with indane units 61 and 62 and unsaturated unit 60 in the main chain (Fig. 10) [20]. Indane unit 61 or unsaturated unit 60 could be selectively obtained under the appropriate reaction conditions [20]. 

Polymerization of a-tv-diolefins has also been investigated to further explore the unusual regiochemistry exhibited by bis(phenoxy-imine) Ti catalysts. Cyclopolymerization of 1,6-heptadiene (see Figure 55) produced a polymer with no observable unsaturations. This indicated quantitative cyclization of the monomer. The NMR analysis of the polymer indicated the presence of ethylene-1,2-cyclopentane units and of methylene-1,3-cyclohexane units in almost... 

Won et al. [19], have reported synthesis of polyesters with valine, leucine, isoleucine, methionine, and phenylalanine (Table 12.1). This three-step process involves synthesis of a diester and a dinitro compound that are copolymerized [19], An amino acid is first coupled with a diol (with 3, 4, or 6 methylene groups) in the presence of tosyl to yield a diester with acid salts of diamine at the terminal ends. The second monomer, di-p-nitrophenyl ester of carboxylic acids, is synthesized by a condensation reaction of adipoyl or se-bacoyl chloride with p-nitro phenol. The final polymerization step involves an arduous condensation reaction in the presence of a strong proton abstractor between acid salt of bis(amino acid-alkyne diester) and di-p-nitrophenyl ester of dicarboxylic acids. Following along the same lines, Chu and Guo [22] have copolymerized a mixture of nitro phenyl ester of succinate, adipate, or sebacate and nitrophenyl fumarate with toluenesulfonic acid salt of phenylalanine butane-1,4-diester. The addition of fumarate derivative to the monomer mixture provides an unsaturated double bond in the polymer backbone that can be functionalized for specific biomedical... 

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