Copolymerization living

A living cationic polymeriza tion of isobutylene and copolymeriza tion of isobutylene and isoprene has been demonstrated (22,23). Living copolymerizations, which proceed in the absence of chain transfer and termination reactions, yield the random copolymer with narrow mol wt distribution and well-defined stmcture, and possibly at a higher polymerization temperature than the current commercial process. The isobutylene—isoprene copolymers are prepared by using cumyl acetate BCl complex in CH Cl or CH2CI2 at —30 C. The copolymer contains 1 8 mol % trans 1,4-isoprene... 

The monomer-selective living copolymerization of /-butyl acrylate (/-BuA) and ethyl methacrylate (EMA) was studied on a 750 MHz spectrometer with an H inverse-geometry LC-NMR probe with pulsed-field gradient coils [10]. The detection volume of the flow cell was ca. 60 pi The measurements were performed in chloroform-di, with a flow rate of 0.2ml/min, at 296 K. The copolymers were obtained using bis (2,6-di-/-butylphenoxy) methylaluminium... 

In this article, we would like to review recent advances in polymer hybrids based on polyolefins and to classify them into four methodologies, namely, PO macroinitiator, PO macromonomer, reactive PO and living copolymerization of olefins, with their well-defined structures and applications. 

Photosensitive azobenzene units were further incorporated into the polyisocyanide 17 by random living copolymerization of the corresponding monomers [64]. The helical polyisocyanide 18 (30 mer) contains 33% azobenzene units as pendants and caused a slight decrease in the UV-visible and CD intensities (8%) upon UV-irradiation. Visible light irradiation effected the reverse photochromic process (Fig. 5). 

Living copolymerization of the electron-poor strained olefins diethyl bicyclo [2.2.1]hepta-2,5-diene-2,3-dicarboxylate and diethyl 7-oxabicyclo[2.2.1]hepta-2,5-di-ene-2,3-dicarboxylate was achieved using palladium(II) neutral initiators such as iodo(endo-6-phenyl-2-norbornene- ndo-5s,2p)(triphenylphosphine)palladium(II)... 

Keywords Living polymerization, Living copolymerization, Rare earth metal complexes, Alkyl methacrylate, Alkyl acrylates, Lactones, Ethylene, 1-Olefins, Conjugated dienes, Acetylene... 

Macosko, C.W., MiUer, D.R. Calculation of average molecular properties during nonlinear, living copolymerization. Makromol. Chem. 192, 377-404 (1991)... 

The amorphous segment of microphase-separated amorphous/liquid crystalline block copolymers may influence the ordering of the mesogens at the interface, as well as the size and discreteness of that interface. Living copolymerizations are therefore being used to determine the effect of the morphology and domain size on the thermotropic behavior of side-chain liquid crystalline block copolymers. 

Since changes in monomer concentration and copolymer composition for any desired yield interval (i.e., from 50%-51%) are difficult to determine, measurements are limited to sufficiently small yield intervals in the region of yield zero (i.e., from 0%-3%). Such a procedure is permissible for stationary states and for copolymerization parameters that do not differ by too much. There are reservations against extrapolating to zero yield for living copolymerizations, since the extrapolation is to low molar masses and to the preferred initiation mechanism. Equation (22-15) converts with the aid of Equation (22-21) to the following for such small yields ... 

Termination and transfer reactions are absent in living copolymerizations. All active species, once formed, remain active over the whole of the polymerization time. If, in addition, the starting step is very fast compared to the propagation step, then all initiator molecules are immediately converted into active species. Thus, in such a case, the sum of the active species concentrations is constant with time and equal to the original initiator concentration ... 

Mixtures of homopolymers must be formed in the absence, or block polymers in the incomplete absence, of a cross-propagation step in such living copolymerizations. Such behavior has been observed in the copolymerization of N-carboxy anhydrides from racemic leucine with primary amines as initiators the sequence analysis was carried out enzymatically. 

Hashimoto and coworkers smdied anionic living copolymerization by ionic mechanism of two monomers, styrene and isoprene in a dilute benzene solution with the aid of combined time-resolved... 

Studies of the living cationic polymerization of isobutylene and copolymerization with isoprene have begun (36,37). The living copolymerization of isobutylene and isoprene has so far produced a random copolymer with narrow molecular weight distribution and a well-defined structin-e. For example, the BClg/ciunyl acetate polymerization system in methyl chloride or methylene chloride at —30°C provides for copolymers with 1-8 mol% trans-l,4-isoprene units and Afn between 2000 and 12,000 with a M /Mn of imder 1.8. The advent of living polymerization... 

Living polymerization is a chain polymerization from which chain transfer and chain termination are absent [96IUP]. Also, the rate of chain initiation is much larger than the rate of chain propagation. The polymers have a very low dispersity and the molar masses are predetermined. A further advantage is the control over the end groups, which allow the synthesis of block copolymers (living copolymerization). 

The most important role of living polymerization is to synthesize block copolymers. The Ti complexes 2—5 activated by dMAO or dMMAO were found to conduct living polymerization of propene, higher l-aUcene, and norbomene as well as their random living copolymerization. Thus, we can synthesize tailor-made copolymers composed of l-aUcene and norbomene with this catalytic system. 

In addition to linear a-olefins, Shino and coworkers reported that 5/MAO catalyzed the living copolymerization of ethylene and norbornene. At 0 °C, 5/MAO can furnish poly(E-co-NB) with 53 mol% norbornene and M = 18 000 g/mol with MJM =1.16 (Hasan et al, 2004b). In addition, a linear increase in with reaction time was observed for this system. At 40 °C, a similar compound, lO/MAO, also provided ethylene-norbomene copolymers with fairly narrow PDls MJM =. 2 -. 21) (Hasan et al, 2004a). 

Shiono and coworkers also reported the living copolymerization of propylene and norbornene with 5/dMAO to produce copolymers with very high Tg values (249 °C) and narrow molecular-weight distributions MJM =. 6) (Hasan et al, 2005). In a later report, the copolymerization of higher a-olefins (1-hexene, 1-octene, and 1-decene) with norbornene by 5/MAO was reported, however, molecular-weight distributions were somewhat broadened (M /Mn= 1.36-1.72) (Shiono et al, 2008). 

Bis(phenoxyimine) titanium complexes have also been employed in the living copolymerization of ethylene/cyclic olefins and ethylene/l,5-hexadiene. Utilizing 31/MAO and varying ethylene pressure, a series of poly(E-co-CP)s with different cyclopentene contents were prepared (Fujita and Coates, 2002). When ethylene pressure was low (<1 psi), an almost perfectly alternating copolymer was formed (Mn = 21000 g/mol, Mw/Mn = 1.34, T = 10.1 C). However, the use of higher ethylene pressures (3 psi) resulted in the formation of a random copolymer containing 36 mol% cyclopentene (M = 133000g/mol,Mw/Mn = 1.24, T =—A.S°C). Tri- and multiblock copolymers were synthesized in which the constituent blocks differed in their cyclopentene content. 

Pan, L., Hong, M., Eiu, J.Y. et al. (2009) Living copolymerization of ethylene with dicyclopentadiene using uitanium catalyst Formation of well-defined polyethylene-block-poly(ethylene-co-dicyclopentadiene)s and their transformation into novel polyolefin-block-(functional polyolefin)s. Macromolecules, 42,4391 393. 

Yoshida, Y, Mohri, J., Ishii, S. et al. (2004) Living copolymerization of ethylene with norbomene catalyzed by bis(pyrrolide-imine) titanium complexes with MAO. Journal of the American Chemical Society, 126,12023-12032. 

Via cationic living copolymerization, iPrOZO as hydrophobic monomer and EtOZO as hydrophilic monomer produced a copolymer P[iPrOZO-co-EtOZO]. Monomer reactivity ratios were determined as riProzo = d Z9 and rEtozo=l Z8, respectively. These values allowed the development of gradient copolymers 8000-10 000) with varying compositions... 

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