Chemo- and Stereoselective Polymerization of Polar Divinyl Monomers by Rare-Earth Complexes

Abstract

Chemoselective polymerization of divinyl monomers is a promising strategy to access functional polymers via postpolymerization, which however, encounters a cross-linking problem. Herein, we report the coordination polymerization of polar divinyl styrenyl monomers 1-(allyloxy)-4-vinylbenzene (AOS), 1-(but-3-en-1-yloxy)-4-vinylbenzene (BOS), 1-(pent-4-en-1-yloxy)-4-vinylbenzene (POS), and 1-(hex-5-en-1-yloxy)-4-vinylbenzene (HOS) by employing the thiophene-fused cyclopentadienyl scandium bis­(alkyl) complexes (2,5-Me2-3-Ph-6H-cyclopenta­[b]­thiophenyl)­Sc­(CH2SiMe3)2THF (1) and (2,4,5,6-Me4-4H-cyclopenta­[b]­thiophenyl)­Sc­(CH2SiMe3)2THF (2) and the pyridinyl methylene fluorenyl rare-earth metal complexes (Py-CH2-Flu)­Sc­(CH2SiMe3)2 (3) and (Py-CH2-Flu)­Y­(CH2SiMe3)2THF (4). Complexes 1 and 2 show high chemoselectivity for these polar divinyl styrenyl monomers across the styrenyl CC bond but give atactic products. Catalysts 3 and 4 exhibit solitary chemoselectivity to give atactic poly­(AOS) but syndiotactic poly­(BOS), poly­(POS), and poly­(HOS). The copolymerization of the polar divinyl styrenyl monomers with ethylene (E) mediated by 3 exhibits chemoselectivity to afford POS/E and HOS/E copolymers but homopolymer poly­(AOS). The reasons behind the (co)­polymerization behaviors were investigated by DFT calculation.

Crystalline sulfur-functionalized poly(α-olefin) synthesized by scandium-catalyzed coordination polymerization

“…24 Then, the stereoselective (co)polymerization of a series of unprotected polar monomers using a rare earth catalyst to afford stereoregular and sequence-controlled polymers was reported by this group. [25][26][27][28][29][30][31][32][33][34][35][36] Our group shown that rare earth catalysts can be used for the stereoselective polymerization of polar 2-vinylpyriding (2-VP). The coordination of a nitrogen atom as well as an olefin CvC bond to the metal center was essential to achieve reactivity and stereoselectivity.…”

The synthesis and properties research of functionalized polyolefins

“…However, previous reports showed that it was changeable to insert two vinyl CQC bonds into a polymer chain, which always had one unattached CQC bond (Scheme 1b). 39,40 On the other hand, tandem ring-opening metathesis polymerization (ROMP) and hydrogenation represent another powerful strategy to access functionalized polyolefin. 41,42 In 2002, Grubbs and coworkers developed a ring-opening-insertion metathesis polymerization of cycloolefins and diene monomers to prepare a family of copolymers.…”

Syndiospecific Polymerization of o-Methoxystyrene and Its Silyloxy or Fluorine-Substituted Derivatives by HNC-Ligated Scandium Catalysts: Synthesis of Ultrahigh-Molecular-Weight Functionalized Polymers

“…The coordination (co)­polymerization of polar olefins to prepare high functional polyolefins having superior surface properties, adhesion properties, and compatibility with other types of materials has always been a challenging and high-profile issue in academia and industry. − The most serious difficulty lies in the fact that the high oxyphilic early transition metal catalysts can be easily poisoned by polar olefins because the stronger Lewis basic heteroatom groups of polar olefins have more preferential coordination ability than the weaker Lewis basic double bond to the strong Lewis acidic metal centers. − Subsequently, the low oxyphilic late transition metal catalysts, which are more tolerant of heteroatom functionalities in the monomer and the polymer, have ascended on the history stage and gradually began to open up new areas for the coordination (co)­polymerization of polar olefins such as polar norbornene, acrylates, vinyl ethers, vinyl acetate, vinyl halides, acrylonitrile, CO, etc. − Recently, a significant breakthrough in the coordination (co)­polymerization of polar olefins has been made by the high oxyphilic rare-earth metal catalysts. − Activated by a catalytically equimolar amount of cocatalyst borate and/or an excess of AlR 3 , rare-earth metal alkyl cations [LLnR] + generated from a series of rare-earth metal dialkyl complexes LLnR 2 L' n (Ln is a rare earth metal center, L is a negative monovalent multi-dentate supporting ligand, R is a negative monovalent alkyl ligand, L' n is a neutral ligand like tetrahydrofuran (THF) solvent molecules with a number in the range of 0–2) exhibit high activities and stereoselectivities in the coordination (co)...…”

“…Then, half-sandwich titanium trialkyl or trichloride catalysts could promote the coordination polymerization of protected polar styrene (Scheme a). Recently, half-sandwich fluorenyl, cyclopentadiene, or indene yttrium dialkyl complexes and non-metallocene quinolyl anilido-ligated yttrium dialkyl complexes have been reported as highly efficient catalysts in the syndiospecific coordination polymerization of polar styrenes, affording syndiotactic poly­(polar styrene)­s with moderate molecular weights and molecular weight distributions (Scheme b). − However, despite these advances, known rare-earth metal catalyst types are limited and their application in catalyzed syndiotactic polymerization of multi-substituted polar styrenes is rare . Most importantly, ultrahigh-molecular-weight syndiotactic poly­(polar styrene)­s have never been achieved to our knowledge.…”