Copolymerization sequential monomer addition

Multiblock copolymeric structures containing PCHD blocks were also synthesized using s-BuLi as the initiator and either TMEDA or DABCO as the additive. Sequential monomer addition was performed with CHD being the last monomer added in all cases [35]. The structures prepared are PS-b-PCHD, PI-fc-PCHD and PBd-b-PCHD block copolymers, PS-fo-PBd-fo-PCHD, PBd-fr-PS-b-PCHD and PBd-fo-PI-fr-PCHD triblock terpolymers, and PS-fc-... 

This observation is corroborated with what has been found in Figures 8-10. There is more of an inversion phenomenon occurance at 20°C. However, the difference between 30°C and 40°C is small and apparently similar, within experimental error. Nevertheless, the new established reactivity ratios of butadiene and isoprene at all three temperatures differ by a smaller factor than what were reported by the work of Korotkov (8) (e.g. rj - 3.38 and 2 = 0.47). Moreover, butadiene is more reactive and initial copolymer contains a larger proportion of butadiene randomly placed along with some incorporation of isoprene units. The randomness of the copolymer via direct copolymerization has been confirmed by the comparison with pure diblock copolymer produced by sequential monomer addition. Both copolymers have similar chemical composition (50/50) and molecular weight. Their... 

Efforts to apply lanthanide metal catalysts for diene/non-diene block copolymerization by sequential monomer addition were reported for samarium catalysts (comparable to Nd) [658] and Nd catalysts [659-661]. In both cases the efforts towards the preparation of block copolymers comprising a poly(diene) building block (BD or IP) and a poly-e-caprolactone build-... 

Living cationic sequential block copolymerization is one of the simplest and most convenient methods to provide well-defined block copolymers. The successful synthesis of block copolymers via sequential monomer addition relies on the rational selection of polymerization conditions, such as Lewis acid, solvent, additives, and temperature, and on the selection of the appropriate order of monomer addition. For a successful living cationic sequential block copolymerization, the rate of crossover to a second monomer ( ) must be faster than or at least equal to that of the homopolymerization of a second monomer (i p). In other words, efficient crossover could be achieved when the two monomers have similar reactivities or when crossover occurs from the more reactive to the less reactive monomer. When crossover is from the less reactive monomer to the more reactive one a mixture of block copolymer and homopolymer is invariably formed because of the unfavorable Rcr/Rp ratio. The nucleophilicity parameter (N) reported by Mayr s group might be used as the relative scale of monomer reactivity [171]. 

Butadiene and isoprene were copolymerized with lanthanide catalysts to raindom and block copolymers via the methods of initial monomer charge and the sequential monomer addition, respectively.io The lanthanide catalyst systems offer several unique features in the copolymerization of B and I monomers, such as ... 

In 2006, Cai et al7 were able to show that 17/MAO could also copolymerize propylene and NB in a living fashion to form random and block copolymers. For example, three sPP-Wocfe-poly(P-co-NB) diblock copolymers were synthesized through sequential monomer addition that had similar molecular weights (Mn 20000gmol", Mw/M = 1.21-1.32). 

Using 50/MAO, Hustad and Coates reported the living copolymerization of propylene and 1,5-hexadiene to produce random copolymers comprised of units of propylene, MCP, and 3-VTM. Through sequential monomer addition, an sPP-blocfe-poly(P-co-MCP-co-3-VTM) diblock copolymer was synthesized with 50/MAO (Scheme 9). The molecular weight distribution of the block copolymer was low (M /Mn = l.ll, Mn = 93 300gmol ) and contained 4.3mol.% MCP units and 2.7 mol.% 3-VTM emits. A poly(E-o>-P)- locfe-poly... 

The copolymerization of dialkyldichlorosilanes was investigated under conditions of concurrent and consecutive monomer addition. The reactivities of the monomers in initiation and propagation reactions were different. Block copolymers may be formed both by sequential addition to existing active centers and by reactivation of existing polymer. These results were combined with previous findings to suggest general schemes for the pathways taken by the reaction. 

The anionic copolymerization (AROCP) of different MSCBs with the monomer of another type capable of anionic polymerization in polar or nonpolar medium initiated by AlkLi mostly yielded random copolymers. The sequential polymerization (addition of the second monomer after polymerization of the first monomer was completed) enabled one to synthesize various block copolymers. As MSCBs, various symmetrically and unsymmetrically substituted derivatives were used. As monomers of other types, styrene, butadiene, isoprene, and 2,4-dimethylstyrene were tested [49]. 

The sequential block copolymerization of la with styrene efficiently proceeded to afford an objective AB diblock copolymer, poly(la)- 7/ocfe-polystyrene, with well-defined structures. This success further confirms the living nature of the anionic polymerization of la. Similarly, a well-defined BA diblock copolymer, polystyrene-l7/ocfe-poly(la), was synthesized by reversing the sequence of monomer addition, namely styrene followed by la. Thus, the possible crossover copolymerization indicates that the electrophilicities of la and styrene as well as the nucleophilicities of both living polymers are very similar. 

Alternating copolymerization of trialkylstannyl methacrylates with MA can proceed via several routes, e.g. by sequential addition of free monomers to the macroradical, by the addition of monomer pairs to a complex or with simultaneous contribution of both free and complex-bound monomers. 

IR absorption spectra were superimposable onto those of the physical mixtures of the respective homopolymers. The molar ratio of the poly(MMA) and polyethylene blocks, however, decreased as the Mn of the prepolymer increased, especially when it exceeded ca. 12 000 at which polyethylene began precipitating as fine colorless particles. It is noteworthy that smooth block copolymerization of ethyl acrylate or methyl acrylate to the growing polyethylene chain (Mn = 6 600-24 800) can be realized by the sequential addition of the two monomers. 

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