Oligomerization, styrene, preparation

A procedure used in the self-branching polymerization reaction for the preparation of dendritic polystyrenes is outlined in Scheme 7. Oligomeric polystyryl-lithium chains are reacted with a coupling agent such as 4-(chlorodimethyl-silyl)styrene (CDMSS), which contains both a polymerizable double bond as well... 

The hydrovinylation reaction, the codimerization of ethene and styrene (Scheme 2), provides easy access to chiral building blocks from inexpensive hydrocarbon feedstocks, which can be used further for the preparation of fine chemicals. Key problems in this reaction include the selectivity of the reaction and the stability of the catalyst. The main side reactions are oligomerization and isomerization of the product to internal achiral alkenes. The latter reaction can be suppressed by... 

Template copolymerization seems to be applied to the synthesis of copolymers with unconventional sequences of units. As it was shown, by copolymerization of styrene with oligomers prepared from p-cresyl-formaldehyde resin esterified by methacrylic or acrylic acid - short ladder-type blocks can be introduced to the macromolecule. After hydrolysis, copolymer with blocks of acrylic or methacrylic acid groups can be obtained. Number of groups in the block corresponds to the number of units in oligomeric multimonomer. Such copolymers cannot be obtained by the conventional copolymerization. 

Analogously, the use of m-divinylbenzene [108-57-6] has been reported (76). However, oligomerization occurs on treatment of divinylbenzene with butyllithium resulting in initiators with functionalities greater than two (68). From a commercial perspective this oligomerization and lack of precise functionality control is not necessarily a problem and useful multifunctional initiators have been prepared from the reaction of butylithium with varying amounts of divinylbenzene (commercial divinylbenzene contains 22% meta, 11%para, and 66% o-, / -, and%ethylvinylbenzene) (77) often in the presence of styrene or diene monomer to provide solubility (seeding technique). 

Nafion-H has also been used as a catalyst for the oligomerization of styrene. The reaction was studied by Higashimura and co-workers.933,934 Hydroxy-terminated poly (alkylene)oxides were prepared by condensation-polymerization of 1,8-octanediol and 1,10-decanediol in the presence of Nafion-H.935 It showed higher activity than sulfuric acid consequently, polymerization could be carried out at lower temperature. 

Oligomeric benzil ketals (DTGPA), prepared by reaction of 2,2-dimethoxy-2-phenyl-acetophenone (DMPA) with triethyleneglycol, in the presence of p-toluen-sulphonic acid, are reported [88] to be efficient in the UV curing of styrene/ unsaturated polyester formulations giving rise to coatings with very low odour. 

Using the same method Storey et al. prepared ionic star—block copolymers.55-58 Styrene was oligomerized followed by the polymerization of butadiene. The living diblock copolymer was subsequently linked with methyltrichlorosilane to provide a three-arm star—block copolymer of styrene and butadiene. Hydrogenation of the diene blocks and sulfonation of the styrene blocks produced the desired ionic star-block structure having ionic outer blocks and hydro-phobic inner blocks, as depicted in Scheme 13. 

Palladium Catalysts. In general, Pd catalysts have considerably lower activities than Ni catalysts in olefin oligomerization. Propylene is selectively dimerized to up to 95% linear hexenes by the catalyst [Pd(acac)2]/Et2AlCl/PR3 in 1,2-dichloroethane. The heterogeneous Pd(II) catalyst system, prepared by treatment of sepiolite with [Pd( 17 -03115)2], exhibits high activity in the styrene dimerization to give exclusively ( )-... 

Styrene oligomers having propyl end groups were prepared by initiating oligomerization with ethyllithium and terminating with 1-bromopropane in ethyl ether ... 

Binary blends prepared by mixing iPP with a fully saturated ahcyclic hydrocarbon resin (obtained by cationic oligomerization of indene, a-methyl styrene, and vinyl toluene, followed by hydrogenation) showed good miscibihty in the melt state (12). 

Oligomeric surfactants have been prepared for use as stalnlizers in emulsion polymerization. Functionalized co-oligomars of acrylonitrile and acrylic acid have been used as surfactants in the emulsion polymoization of butadiene, styrene and itaconic acid [169], Diblock copolymers (oxazoline based) with narrow MMD appeax to be excellmt emulsifiers for the inverse emulsion polymerization of styraie [170], and amphiphilic oligomeric diblock macromonomers (PEO-PPO type) have been relied as steric stabilize in regular styrene emulsion polymraizarion [171]. 

The fact that alcohols are sufficiently nucleophilic to initiate the anionic polymerization of FO (a unique feature, not shared by other epoxides, including styrene oxide), provides a useful way of preparing block, star and graft copolymers from, respectively, diols, polyols and OH-bearing polymers such as cellulose and poly(vinyl alcohol). The FO blocks and grafts however, are oligomeric in size, because transfer reactions limit their growth [4d]. 

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