100828-95-3

Upstream product

• 109088-51-9 2-(4-chloromethylphenyl)propan-2-ol 

Downstream Products

• 109088-43-9 1-(2,2-Dimethyl-3-methylene-cyclopropyl)-4-isopropenyl-benzene 
• 109088-52-0 1-Isopropenyl-4-(2-isopropylidene-cyclopropyl)-benzene 

Relevant academic research and scientific papers

Preparation of polystyrene-polyolefin multiblock copolymers by sequential coordination and anionic polymerization

Block copolymers of polyolefins (PO) and polystyrene (PS) are attractive materials that are not synthesized directly from the olefin and styrene monomers. A strategy for construction of PS-b-PO-b-PS triblock units directly from the olefin and styrene monomers is disclosed herein. PO chains (ethylene/1-octene or ethylene/1-pentene copolymers) were grown from dialkylzinc species bearing the α-methylstyrene moiety (i.e., [4-(isopropenyl)benzyl]2Zn) by 'coordinative chain transfer polymerization (CCTP)' using a typical ansa-metallocene catalyst, rac-[Me2Si(2-methylindenyl)2]ZrCl2 activated with modified-methylaluminoxane (MMAO). PS chains were subsequently grown from the Zn-alkyl sites and from the α-methylstyrene moieties of the resulting PO chains by switching to anionic polymerization. When nBuLi(tmeda)2 was fed into the system as an initiator in a quantity fulfilling the criterion [Li] > [Zn] + [Al in MMAO], nBuLi(tmeda)2 successfully attacked the α-methylstyrene moieties to initiate the anionic styrene polymerization at both ends of the PO chains generated in the CCTP process. However, in model studies, the attack of nBuLi(tmeda)2 on α-methylstyrene in the presence of (hexyl)2Zn consumed two molecules of α-methylstyrene per nBuLi to afford mainly R-CH2C(Ph)(Me)-CH2C(Ph)(Me)Li, where R is either an nbutyl or hexyl group originating from nBuLi or (hexyl)2Zn, respectively. This observation suggests that the block copolymer does not simply comprise the PS-b-PO-b-PS triblock, but instead comprises a multiblock containing PS-b-PO-b-PS units. The molecular weight of the polymer increased after performing anionic polymerization. Even though the phase separation of the PS and PO blocks observed in the TEM images is less regular in the multiblock copolymers, the elastomeric property of the multiblock copolymers observed in the hysteresis testing is better than that of the diblock analogue.

Methylenecyclopropane Rearrangement as a Probe for Free Radical Substituent Effects. ?. Values for Commonly Encountered Conjugating and Organometallic Groups

A series of 3-aryl-2,2-dimethylmethylenecyclopropanes, 8, with NO2, NMe2, vinyl, isopropenyl, phenyl, cyclopropyl, CH2SiMe3, SiMe3, SnMe3, , and HgCl substitution in the para position of the aromatic ring have been prepared.All rearrange thermally to the corresponding isopropylidenecyclopropanes 9 at rates that are substituent dependent.These commonly encountered substituents all enhance rearrangement rates relative to the unsubstituted analogue with p-NMe2 being the most effective.The rate enhancements are interpreted in terms of stabilization of the biradical intermediate by the para substituent.Rate data have allowed the assignment of ?. values for these groups, which have not been previously determined.The nitro group in the para position is also quite effective in increasing the rearrangement rate, which contrasts with the effect of this group on many other free radical reactions.Vinyl is somewhat more effective as a radical stabilizing group than is isopropenyl or phenyl, possibly due to steric interactions in the planar conformations necessary for conjugative stabilization by isopropenyl or phenyl.Trimethylsilyl,trimethylstannyl, and HgCl all enhance the methylenecyclopropane rearrangement rate, but only to a moderate extent.Boron containing substituents, where boron can act as an acceptor group, are among the more effective radical stabilizing groups, as implied by their effect on the rearrangement rate of 8.The cyclopropyl and CH2SiMe3 groups, which also enhance the rearrangement rate of 8 to a moderate extent, become even more effective radical stabilizing groups when present in conjunction with the carbethoxy group.These two conjugating groups are therefore capable of acting as donor groups in captodative radical stabilization.