Syndioselective Polymerization of a BN Aromatic Vinyl Monomer

Mendis, Shehani N.; Zhou, Tiffany; Klausen, Rebekka S.

doi:10.1021/acs.macromol.8b01707

Cited by 16 publications

(22 citation statements)

References 57 publications

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“…Initial efforts focused on Lewis acid catalysts, given the observed stability of BN2VN to Lewis acidic coactivators in coordination polymerization. 16,17 However, a screen of several Al- and B-based Lewis acids known to promote styrene cationic polymerization failed to initiate BN2VN polymerization (Table 1). In contrast to styrene polymerizations conducted as control reactions, only unreacted starting material was observed by 1 H NMR spectroscopy (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…15 We also reported the first example of polymerization of a BN aromatic monomer by a non-radical mechanism; we observed highly syndioselective coordination–insertion polymerization by the action of the cationic complex arising from Cp*TiMe 3 /B(C 6 F 5 ) 3 . 16 Later work by Cui et al found that Sc-complexes were also effective for syndioselective polymerization of BN2VN. 17 The stability of BN2VN to coordination polymerization is notable, given the use of highly Lewis acidic complexes such as B(C 6 F 5 ) 3 or methylalumoxane (MAO), and suggested the potential viability of cationic polymerization.…”

Section: Introductionmentioning

confidence: 99%

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Azaborine benzylic ion stability and reactivity in ionic polymerization

2022

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Azaborine benzylic ion stability and reactivity in ionic polymerization

2022

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“…The resultant polymers are defined by 1 H and 13 C NMR spectrum analyses and assigned according to the literature. [ 24 ] The methine(H1) and methylene protons(H2) of the polymer obtained from 4 show as broad resonances like atactic poly(BN2VN) ( Figure ). Whilst poly(BN2VN) isolated from 5 gives much sharper peaks with distinct splitting, correspondingly, methine carbon C1 provides much sharper resonance as compared with that from 4 ( Figure ), suggesting that 5 is more highly stereoselective than 4 .…”

Section: Figurementioning

confidence: 99%

“…No obvious resonance of mm triads is observed and thus the syndiotacticity value of rr = 90% was calculated according to the integral value of the rr triads, to our knowledge, which is the highest value. [ 7,24 ]…”

Section: Figurementioning

confidence: 99%

Stereoselective Polymerization of an Aromatic Vinyl Monomer to Access Highly Syndiotactic Poly(vinyl alcohol)

Huang

Jiang

Zhang

et al. 2020

Macromol. Rapid Commun.

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increase of crystallinity. [5] Radical or reversible addition-fragmentation chain transfer (RAFT) polymerization of vinyl esters (VA cannot exist as a stable chemical) followed by hydrolysis of resultant poly(vinyl ester) could only give syndio-enriched PVA (r = 78%). [6,7] Known that coordination polymerization is the most efficient manner to access highly stereoregular polymers, with respect of the polar vinyl esters; however, it suffers a serious problem that the catalyst is easily poisoned by the polar groups. To date copolymerizations of ethylene with a wide range of polar monomers have been achieved by protecting or separating the polar groups from contacting with the active species [8][9][10] or using late transition metal catalysts of tolerance to polar groups. [11][12][13][14][15][16] However, both the activity and the selectivity decrease obviously, and low molecular weight products containing a small amounts of polar monomer are always obtained. Regarding to homopolymerization of polar monomers, it is still a research topic far from success, although recent reports demonstrate that polar groups, in some cases, do not poison but activate the catalysts to afford high molecular weight and highly regular homo-or copolymers. [17,18] We wish to solve this problem in an alternative method by employing vinyl monomers containing nonpolar but "reactive" substituent to perform stereoselective polymerization, and then transferring the substituent into other functional groups through postpolymerization modification. [19,20] Vinyl compounds bearing boraza (BN) aromatic ring are such monomers where the amino nitrogen with high coordinative capacity is well protected by the single intramolecular boron atom instead of a bulky substituent; boron atom in the aromatic ring can be easily transformed into other group without racemizing the potential chirality of the adjacent carbon atom, thus the stereoregularity of resulting polymers is remained after postpolymerization modification. A series of BN containing monomers such as BN-styrene and BN-vinylbiphenyl are reported to polymerize via RAFT mechanism. [21,22] 2-Vinyl-2,1-borazanaphthalene (BN2VN) can be homo-and copolymerized with 2-vinylnaphthalene via radical catalysts to give high molecular weight polymers while it can only be homopolymerized in moderate syndioselectivity by titanium catalysts. Noted that, in all the above cases long reaction times are required. [23][24][25][26] Recently, rare-earth metal based catalytic systems have been reported to be extraordinary tolerance toward polar groups, which exhibit high activity and excellent stereo-selectivity for homo-and copolymerizations of polar styrenes. [17,18,[27][28][29][30][31][32][33][34] We Streoregular poly(vinyl alcohol) is hard to obtain because vinyl alcohol is unstable relative to its tautomer acetaldehyde, and the monomer precursor vinyl ester is poisonous to the coordination catalyst. Herein, the coordination poly merization of 2vinyl2,1borazanaphthalene (BN2VN) is reported by the linked or unlinked hal...

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“…A possible strategy to overcome the inherent differences in the reactivity of two monomers in radical copolymerization is to exploit a post-polymerization modification reaction that is specific for one type of monomer unit. [13][14][15][16][17][18][19] In this manner, copolymerization of two monomers with similar polymerizability can lead to polymeric precursors for copolymers with compositions and microstructures that are inaccessible by direct copolymerization. Indeed, post-polymerization methods [20][21][22][23][24] to produce polymers and copolymers containing olefins have been recently reported via either deoxygenation of poly(methyl acrylate) 25 or post-functionalization and subsequent grafting-from polymerization from polyethylene or polypropylene.…”

Section: Introductionmentioning

confidence: 99%