Radical polymerization of 'dehydroaspirin' with the formation of a hemiacetal ester skeleton: a hint for recyclable vinyl polymers

A vinyl polymer with a cyclic hemiacetal ester skeleton was synthesized via the radical polymerization of 2-methylene-4H-benzo [d][1,3] dioxin-4-one (MBDO; so-called ` dehydroaspirin'). This material could be decomposed to acetic acid and salicylic acid (the raw ingredients for MBDO) by acid hydrolysis, and thus has potential as a recyclable vinyl polymer.ArticlePOLYMER CHEMISTRY.10(22):2764-2768(2019)journal articl

Stereospecific Anionic Polymerization of α-(Hydroxymethyl)acrylate with Protective Group

Anionic polymerizations of hydroxyl-protected α-(hydroxymethyl)acrylates were investigated. The methyl ester with methoxymethyl (1-MOM) and allyl (1-allyl) protecting groups were polymerized by isopropyl α-lithioisobutyrate (Li-iPrIB) in toluene at −78 °C, affording highly isotactic polymers. Similarly, the polymerization of ethyl ester (2-MOM) gave an isotactic polymer, while those of t-butyl (3-MOM) and isobutyl (4-MOM) ester did not form any polymeric products. The hydrolysis of poly(2-MOM) in acidic conditions resulted in the deprotection of MOM group, although the acid also catalyzed the ester exchange between the neighboring units to form lactone units, as observed by 1H NMR analysis, IR spectroscopy and thermogravimetric analysis. A film of poly(2-MOM) exposed to HCl vapor for 2 h became insoluble in any organic solvents due to the lactonization in solid state.ArticleMacromolecular Symposia.350(1):86-98(2015)journal articl

Termination of Living Anionic Polymerization of Butyl Acrylate with alpha-(Chloromethyl) acrylate for End-Functionalization and Application to the Evaluation of Monomer Reactivity

Article first published online: 11 JUN 2015Anionic polymerization of n-butyl acrylate (nBA) in toluene initiated with a binary initiator, isopropyl α-lithioisobutyrate/ethylaluminum bis(2,6-di-tert-butylphenoxide) at −60 °C, is terminated with ethyl α-(chloromethyl)acrylate (ECMA) to afford a poly(nBA) possessing an acryloyl group at the terminal with 80% of termination efficiency. The reactivity of nBA against a polymer anion of methyl methacrylate formed under identical conditions is estimated relative to the termination with ECMA by reacting a mixture of nBA and ECMA followed by 1H NMR spectroscopic chain-end analysis; the relative reactivity of nBA is found 80 times or more higher than ECMA.ArticleMACROMOLECULAR CHEMISTRY AND PHYSICS. 216(14):1534-1539 (2015)journal articl

Stereoregular poly (methyl methacrylate) with double-clickable ω-end: synthesis and click reaction

Isotactic and syndiotactic poly(methyl methacrylate)s with orthogonally double-clickable terminal ends, that is, α,β-unsaturated esters for Michael addition-type thiol–ene reactions and azide or alkynyl groups for azide–alkyne click reactions, were prepared via a terminating reaction of stereospecific anionic polymerization with propargyl and 2-chloroethyl α-(chloromethyl)acrylates. The subsequent polymer modification via a double click reaction proceeded quantitatively in a one-pot system under ambient conditions. The facile and almost quantitative double-end-functionalization would open a new material design based on stereoregular PMMAs with controlled molecular weights.ArticlePolymer Chemistry.6(19):3601-3607(2015)journal articl

alpha-(Aminomethyl)acrylate: polymerization and spontaneous post-polymerization modification of beta-amino acid ester for a pH/temperature-responsive material

First published online 16 Jun 2015Ethyl α-(aminomethyl)acrylate, a β-amino acid ester carrying a conjugated vinylidene group at the α-position, was radically polymerized. The polymerization was found to involve subsequent ester–amide exchange reaction between the amino pendants of the polymer and an ester group of the monomer, affording acrylamide-bearing units in 11–15% contents. The obtained polymer exhibited pH/temperature responsiveness in aqueous media.ArticlePOLYMER CHEMISTRY. 6(28):5026-5029 (2015)journal articl

Synthesis of poly(conjugated ester)s by ring-opening polymerization of cyclic hemiacetal ester bearing acryl skeleton

Available online 20 August 2019Ring-opening polymerization (ROP) of 2,6-dimethyl-5-methylene-1,3-dioxan-4-one (DMDO), a cyclic hemiacetal ester containing an acrylate skeleton, was investigated. Although the ROPs catalyzed by tin(II) 2-ethylhexanoate [Sn(Oct)(2)] and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) did not yield polymeric products, diphenyl phosphate (DPP) functioned a catalyst for the ROP through acyl scission accompanying with the elimination of acetaldehyde at 50 degrees C and 80 degrees C. The resulting polymer was a poly(conjugated ester) that had similar structure to the polymer of alpha-methylene-beta-butyrolactone (M beta BL), an alpha-exomethylene lactone with four-membered ring. Copolymerizations of epsilon-caprolactone and delta-valerolactone were also performed to yield the corresponding polyesters. The chemoselective main chain scission of the copolymers at the conjugated ester units were achieved by conjugate substitution reaction with benzyl mercaptan. Although the ROP of DMDO left a problem in the control of molecular weight, DMDO exhibited a potential as an easier accessible monomer alternative to M beta BL for the preparation of bio- and chemo-degradable polyesters.ArticleEUROPEAN POLYMER JOURNAL.120:109185(2019)journal articl

Polythioethers bearing side groups for efficient degradation by E1cB reaction : reaction design for polymerization and main-chain scission

We have previously reported the polycondensation by the tandem reactions of dithiols and α-(bromomethyl)acrylates, consisting of conjugate substitution (SN2′ reaction) and conjugate addition (Michael addition) reactions. The resulting polythioethers underwent a main-chain scission (MCS) by E1cB reaction, which is the reverse reaction of conjugate addition, although it was not quantitative due to the equilibrium. Herein, the modification of the structures of polythioethers led to irreversible MCS, whereby the β-positions of ester moieties were substituted with a phenyl group. This slight modification in the polymer structure influenced the monomer structures and polymerization mechanisms. The understanding of reaction mechanisms by model reactions was required to obtain high molecular weights of polythioethers. It was clarified that the consequent additions of 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and PBu3 were effective to achieve high molecular weight. The resulting polythioethers decomposed by irreversible MCS via E1cB reaction with DBU

α-exomethylene lactone possessing acetal–ester linkage: Polymerization and postpolymerization modification for water-soluble polymer

First published: 16 October 20152,6-Dimethyl-5-methylene-1,3-dioxa-4-one (DMDO), a cyclic acrylate possessing acetal–ester linkage, was obtained as a mixture of cis- and trans-isomers (95:5) from Baylis–Hillman reaction of an aryl acrylate. The radical and anionic polymerizations of DMDO yielded the corresponding vinyl polymers without any side reactions such as cleavage of the acetal–ester linkage. The polymerization behaviors were significantly different from that of the acyclic acrylate, α-(hydroxymethyl)acrylic acid, which was expected inactive against polymerization due to the steric hindrance around the vinylidene group by the α-substituent. The acetal–ester linkage of the obtained polymer (P1) was completely cleaved via acid hydrolysis to afford a water soluble polymer, P2. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 955–961ArticleJournal of Polymer Science Part A: Polymer Chemistry. 54(7):955-961 (2016)journal articl

Synthesis and post-polymerization reaction of end-clickable stereoregular polymethacrylates via termination of stereospecific living anionic polymerization

Poly(methyl methacrylate)s with high stereoregularity and clickable end-groups were synthesized via terminating reactions with α-(halomethyl)acrylates in stereospecific living anionic polymerization. The terminating reaction was efficient and tolerant to the reaction conditions to such an extent that almost quantitative end-functionalization was achieved in isotactic- and syndiotactic-specific polymerization systems. The terminating reactions were also achieved in polymerizations of vinyl methacrylate and trimethylsilyl methacrylate. For the polymerization of butyl acrylate, however, the termination efficiency was limited to less than 69%. Furthermore, the quantitative end-functionalization of the incorporated C[double bond, length as m-dash]C double bond at ω-end was achieved with various thiols catalyzed by Et3N. The base-catalysed thiol–ene reaction of the stereoregular poly(vinyl methacrylate) with a ω-end C[double bond, length as m-dash]C double bond selectively proceeded to retain vinyl ester functions, and the subsequent hydrolysis afforded ω-functional stereoregular poly(methacrylic acid). A combination of the terminating agent with a protected lithium amide afforded stereoregular poly(methyl methacrylates) with orthogonally clickable α- and ω-ends.ArticlePolymer Chemistry.6(7):1078-1087(2015)journal articl