Isobutyl vinyl ether molecular weight

Maleate/vinyl ether formulations based on a model unsaturated polyester prepared from maleic anhydride and 1,5-pentane diol and triethylene glycol divinyl ether were studied. At molecular weights of less than about 10,000 the cured films were extremely brittle. When the equivalent weight of the unsaturated polyester was increased by replacing some of the maleic anhydride with succinic anhydride, measurable values for film elongation could be obtained but the cure speed was definitely slower. When either diethyl maleate or isobutyl vinyl ether were added as monofunctional diluents the cure dose needed to obtain 200 MEKDR was increased and the flexibility measured by pencil hardness increased as the amount of diluent was increased. A urethane vinyl ether was synthesized and used to replace DVE-3 and films with increased elongation were obtained at equivalent at dosages as low as 1 J/cm2. 

Initiation with Tropylium Ion. Tropylium hexachlorantimonate reacts with vinyl alkyl ethers in a manner very similar to the reactions of triphenylmethyl salts. Again, rapid initiation is followed by propagation without apparent termination. Termination can be demonstrated to be absent from experiments in which fresh samples of monomer are added to completed polymerizations, whereupon the measured reaction rates parallel those previously recorded (Table II). Molecular weights of the polymers from isobutyl vinyl ether are very similar to those obtained with triphenylmethyl salts as initiators and again give clear evidence for excessive monomer transfer. Gas chromatographic analysis of the reaction mixtures showed that cycloheptatriene (product of hydride abstraction) was not present which indicates clearly that initiation must arise via addition of the tropylium ion to the vinyl ether—i.e.,... 

Thus, by lowering solvent polarity (CH2Cl2/CCl4 mixtures) or by the addition of a common ion salt (rtBtuNI), these researchers obtained poly(pMOS) of unimodal and relatively narrow MWDs, whose shape and position corresponded to those of the lower polymer population in the two-peaked distribution. Under these conditions the number-average molecular weights increase with conversion. Upon sequential addition of fresh monomer feeds, and block copolymers of pMOS and isobutyl vinyl ether (IBVE) are obtained [52], Similar results were also obtained for the polymerization of IBVE [53,54]. 

Combination of a living ionic polymerization and a metal-catalyzed radical polymerization also leads to comb polymers, where both the molecular weights of the arm and main-chain polymers are well controlled. PMMA with poly(vinyl ether) arm polymers of controlled molecular weights (C-l) were prepared by the copper-catalyzed radical polymerization of methacrylate-capped macromonomers carrying a poly-(isobutyl vinyl ether), which were obtained by living cationic polymerization with a methacryloxy-capped end-functionalized initiator.428 Comb polymers with... 

Heterogeneous conditions, due to poor solubility of heteropoly acid, in polymerization of isobutyl vinyl ether with H3PW12O40 in CH2CI2 were also studied. When bases like 1,4-dioxane or tetrahy-drofuran were present the molecular weight distributions were very broad. By contrast, polymerizations in the presence of dimethyl sulfide at —30°C yielded living polymerizations of the ether. Here too, the product had very narrow molecular weight distribution [139]. In summary, some typical features of living cationic polymerizations are ... 

Living cationic polymerization of vinyl ethers initiated by an SnCU/RCl catalytic system can be carried out in a continuous microflow system, which consists of a mutilamination micromixer M (channel width = 40 pm, IMM) and a microtube reactor R (Figure 14.1). A solution of a monomer and RCI is mixed with a solution of SnCU using the micromixer at —78 °C and the resulting mixture was allowed to react in the microtube reactor at the same temperature. For example, isobutyl vinyl ether (IBVE) was polymerized using functionalized initiators to obtain end-functionalized polymers of narrow molecular weight distribution (Mw/M < 1.2) (Scheme 14.4). 

The present cation pool-initiated polymerization using a microflow system can be applied to other vinyl ethers such as isobutyl vinyl ether (IBVE) and tert-butyl vinyl ether (TBVE) (Table 14.2). The corresponding macroscale batch polymerization results in much poorer molecular weight distribution control. 

Trifluoromethanesulfonic acid (TfOH) is an effedive initiator for cationic polymerization. For example, TfOH-initiated polymerization of isobutyl vinyl ether (IBVE) in 1,2-dichloroethane using a macroscale batch system (20 mL scale) [46] is complete within lOsat—25°C. The molecular weight distribution is, however, rather broad and Mw/Mn ranges from 2.73 to 4.71, presumably because of chain transfer readions due to the high readivity of the polymer ends. 

Proton transfer to monomer in the polymerization of a-methyl styrene can be suppressed by the presence of 2,6-di-t-butyl pyridine. This scavenges all the protons and effectively converts the reaction from a transfer to a termination reaction. The copolymerization of crmethyl styrene with isobutyl vinyl ether - has shown how the relative reactivities of carbenium and carboxonium ions affect conversion and molecular weights. Other interesting studies include the polymerization of substituted cs-methyl styrenes - and the stereospecific polymerization of anethole. ... 

Vinyl Ethers.—Two studies on the polymerization of isobutyl vinyl ether highlight the large differences possible in mechanism when different initiators are employed. Thus, with iodine," propagation from free ions and ion-pairs described the kinetics and molecular weights adequately, while with trifluoroacetic acid the system appeared to be pseudocationic with a monomer-solvated covalent ester as the predominant chain-carrier. 

In the presence of zinc chloride (as an activator), for example, diphenyl phosphate (as an initiator) rapidly and quantitatively polymerizes isobutyl vinyl ether (IBVE) in toluene at 0 C. As shown in Figure 1, the of the produced polymers is directly proportional to monomer conversion and in good agreement with the calculated value based on the feed molar ratio of IBVE to the initiator (one polymer chain per phosphate). On addition of a second feed of IBVE at the end of the polymerization, polymer molecular weight further increases with conversion, while the polymers invariably exhibit very narrow MWDs (M /Mj < 1.1). All these data show that the diphenyl phosphate/ ZnCl2 initiating system induces living polymerization of IBVE. 

Interesting results have been observed by investigating complexes of some poly-vinyl-ethers with tri-isobutyl aluminum. It was noticed that the variation of the optical activity on complexing poly-vinyl-ethers with tri-isobutyl aluminum is of the same type as in the low-molecular-weight model compounds (66, 111, 113b, 123). 

Poly (vinyl isobutyl ether) obtained this way is the typical, low molecular weight, (MW = 2000-8000) amorphous material normally... 

Poly(vinyl ethers). Homopolymers of vinyl ethers are produced via carbocationic polymerization. Polymerization is carried out either in bulk or solution using BF3 or its complexes, AICI3, or SnCh. Commercially important poly(vinyl ethers) are made of methyl, ethyl, isobutyl, and octadecyl vinyl ethers [Tg = -34, -42, -19, and 50°C (1)]. Depending on their glass-transition temperature and molecular weight, commercial poly(vinyl ethers) are viscous oils, tacky resins, or... 

In G.A.F. laboratories at Easton, Pa., our evaluation of German methods for polymerizing alkyl vinyl ethers to obtain pressure sensitive adhesives led to the discovery of stereoregulation. I first disclosed in 19 6 that differences in cationic polymerization conditions gave differences in properties in vinyl isobutyl and vinyl methyl ether polymers which could not be attributed to molecular weight but must result from different chemical structures, e.g., stereoisomerism . Although Staudinger had not predicted stereo-... 

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