Ring‐Opening and polymerization of 1‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotrisiloxane

1‐[2′‐(Heptaphenylcyclotetrasiloxanyl)ethyl]‐1,3,3,5,5‐pentamethylcyclotetrasiloxane ( II ) was prepared from 1‐[2′‐(methyldichlorosilyl)ethyl]‐1,3,3,5,5,7,7‐heptaphenylcyclotetrasiloxane ( I ) and tetramethyldisiloxane‐1,3‐diol. Acid‐catalyzed ring‐opening of II in the presence of tetramethyldisiloxane gave 1,9‐dihydrido‐5‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( III ) and 1,9‐dihydrido‐3‐[2′‐(heptaphenylcyclotetrasiloxanyl)ethyl]nonamethylpentasiloxane ( IV ). Both acid‐ and base‐catalyzed ring‐opening polymerization of II gives highly viscous, transparent polymers. The structures of I – IV and polymers were determined by UV, IR, ¹H, ¹³C, and ²⁹Si NMR spectroscopy. In addition, molecular weights obtained by GPC and NMR end group analysis were confirmed with mass spectrometry. On the basis of ²⁹Si NMR spectroscopy, the polymers appear to result exclusively from ring‐opening of the cyclotrisiloxane ring. No evidence for ring‐opening of the cyclotetrasiloxane ring was observed. Polymer properties were determined by DSC and TGA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 137–146, 2006     

Photoinduced cationic ring‐opening frontal polymerizations of oxetanes and oxiranes

The photoinitiated cationic ring‐opening polymerizations of certain epoxides and 3,3‐disubstituted oxetanes display the characteristics of frontal polymerizations. When irradiated with UV light, these monomers display a marked induction period, during which little conversion of the monomer to the polymer takes place. The local application of heat to an irradiated monomer sample results in polymerization that occurs as a front propagating rapidly throughout the entire reaction mass. For the characterization of these frontal polymerizations, the use of a new monitoring technique, employing optical pyrometry, has been instituted. This method provides a simple, rapid means of following these fast polymerizations and quantitatively determining their frontal velocities. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1630–1646, 2004     

Modification of proline‐based 2,5‐diketopiperazines by anionic ring‐opening polymerization

2,5‐Diketopiperazines (DKPs) are the smallest cyclic dipeptides found in nature with various attractive properties. In this study, we have demonstrated the successful modification of proline‐based DKPs using anionic ring‐opening polymerization (AROP) as a direct approach. Four different proline‐based DKPs with various side chains and increasing steric hindrance were used as initiating species for the polymerization of 1,2‐epoxybutane or ethoxyethyl glycidyl ether in the presence of t‐BuP₄ phosphazene base. The addition of a Lewis acid, tri‐isobutyl aluminum, to the reaction mixture strongly decreased the occurrence of side reactions. Impact of the DKP side‐chain functionalities on molar mass control and dispersity was successfully evidenced. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1008–1016     

Sequence‐controlled cationic ring‐opening copolymerization of spiroorthocarbonate and oxetane

Pseudo block and triblock copolymers were synthesized by the cationic ring‐opening copolymerization of 1,5,7,11‐tetraoxaspiro[5.5]undecane (SOC1) with trimethylene oxide (OX) via one‐shot and two‐shot procedures, respectively. When SOC1 and OX were copolymerized cationically with boron trifluoride etherate (BF₃OEt₂) as an initiator in CH₂Cl₂ at 25 °C, OX was consumed faster than SOC1. SOC1 was polymerized from the OX‐rich gradient copolymer produced in the initial stage of the copolymerization to afford the corresponding pseudo block copolymer, poly [(OX‐grad‐SOC1)‐b‐SOC1]. We also succeeded in the synthesis of a pseudo triblock copolymer by the addition of OX during the course of the polymerization of SOC1 before its complete consumption, which provided the corresponding pseudo triblock copolymer, poly[SOC1‐b‐(OX‐grad‐SOC1)‐b‐SOC1]. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3233–3241, 2006     

Synthesis and application as polymer electrolyte of hyperbranched polyether made by cationic ring‐opening polymerization of 3‐{2‐[2‐(2‐hydroxyethoxy)ethoxy]ethoxymethyl}‐3′‐methyl‐oxetane

A novel cyclic ether monomer 3‐{2‐[2‐(2‐hydroxyethoxy)ethoxy]ethoxy‐methyl}‐3′‐methyloxetane (HEMO) was prepared from the reaction of 3‐hydroxymethyl‐3′‐methyloxetane tosylate with triethylene glycol. The corresponding hyperbranched polyether (PHEMO) was synthesized using BF₃·Et₂O as initiator through cationic ring‐opening polymerization. The evidence from ¹H and ¹³C NMR analyses revealed that the hyperbranched structure is constructed by the competition between two chain propagation mechanisms, i.e. active chain end and activated monomer mechanism. The terminal structure of PHEMO with a cyclic fragment was definitely detected by MALDI‐TOF measurement. A DSC test implied that the resulting polyether has excellent segment motion performance potentially beneficial for the ion transport of polymer electrolytes. Moreover, a TGA assay showed that this hyperbranched polymer possesses high thermostability as compared to its liquid counterpart. The ion conductivity was measured to reach 5.6 × 10^?5 S/cm at room temperature and 6.3 × 10^?4 S/cm at 80 °C after doped with LiTFSI at a ratio of Li:O = 0.05, presenting the promise to meet the practical requirement of lithium ion batteries for polymer electrolytes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3650–3665, 2006     

Synthesis and ring‐opening polymerizations of novel S‐glycooxazolines

A new 2‐oxazolines containing S‐galactosyl substituents linked to alkyl chains of different lengths; (S‐glycooxazoline) were prepared relatively in high yields. By using a 1:1 adduct of 2‐methyl‐2‐oxazoline and methyl triflate, as the initiator, the monomer was polymerized via ring‐opening polymerization (ROP) to give products with relatively narrow molecular weight distributions. Homo‐ and copolymerization were performed, and the kinetics of these new S‐glycooxazolines in the ROP are investigated. After a quantitative deprotection, poly(2‐oxazoline)s having pendant carbohydrate were obtained. The interaction of the poly(S‐glycooxazoline) with RCA₁₂₀ lectin was investigated, the binding constant between glycopolymer and lectin was increased by 10² times compared with that of the monosaccharide (D ‐galactose). The in vivo expression of green fluorescent protein using the synthesized poly(S‐glycooxazoline)s as polymeric inducers in Escherichia coli host were performed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and chemical modification of hyperbranched polyethers with terminal hydroxy groups by the anionic ring‐opening polymerization of 3‐alkyl‐3‐hydroxymethyl oxetanes

The anionic ring‐opening polymerization of oxetanes containing hydroxyl groups was carried out with potassium tert‐butoxide as an initiator in the presence of 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding multifunctional hyperbranched polymers: poly(3‐ethyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 2200–4100 in 83–95% yields, and poly(3‐methyl‐3‐hydroxymethyloxetane)s, with number‐average molecular weights of 4600–5200 in 70–95% yields. The synthesized poly(3‐ethyl‐3‐hydroxymethyloxetane)s and poly(3‐methyl‐3‐hydroxymethyloxetane)s were hyperbranched polyethers containing an oxetane moiety and many hydroxy groups at the ends. The postpolymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane)s was performed in the presence of potassium tert‐butoxide and 18‐crown‐6‐ether in N‐methylpyrrolidinone at 180 °C; it yielded corresponding polymers with higher molecular weights in good yields. The cationic polymerization of poly(3‐ethyl‐3‐hydroxymethyloxetane) derivatives was carried out with boron trifluoride etherate as an initiator and was followed by alkaline hydrolysis; this yielded a new branched polymer, a poly(hyperbranched polyether), with many pendant hydroxy groups. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3739–3750, 2004     

Synthesis of novel hyperbranched polymer through cationic ring‐opening multibranching polymerization of 2‐hydroxymethyloxetane

The cationic ring‐opening multibranching polymerization of 2‐hydroxymethyloxetane ( 1 ) as a novel latent AB₂‐type monomer was carried out using trifluoromethane sulfonic acid or trifluoroboron diethyl etherate by a slow‐monomer‐addition (SMA) method. The polymer yield of poly‐1 ranged from ca. 58–88%, which increase with the increasing monomer addition time on the SMA method. The absolute molecular weights (M_w,MALLS) and the polydispersities of poly‐1 were in the range of 8,000–43,500 and 1.45–4.53, respectively, which also increased with the increasing monomer addition time. The Mark‐Houwink‐Sakurada exponents α in 0.2 M NaNO₃ aq. were determined to be 0.02–0.25 for poly‐1 , indicating that poly‐1 has compact forms in the solution because of the highly branched structure. The degree of the branching value of poly‐1 , which was calculated by Frey's equation, ranged from ca. 0.50 to 0.58, which increased with the increasing monomer addition time. The steady shear flow of poly‐1 in aqueous solution exhibited a Newtonian behavior with steady shear viscosities independent of the shear rate. The results of the MALLS, NMR, and viscosity measurements indicated that poly‐1 is composed of a highly branched structure, i.e., the hyperbranched poly (2‐hydroxymethyloxetane). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of block and end‐functionalized polyesters by triflimide‐catalyzed ring‐opening polymerization of ε‐caprolactone, 1,5‐dioxepan‐2‐one,and rac‐lactide

The ring‐opening polymerization (ROP) of cyclic esters, such as ε‐caprolactone, 1,5‐dioxepan‐2‐one, and racemic lactide using the combination of 3‐phenyl‐1‐propanol as the initiator and triflimide (HNTf₂) as the catalyst at room temperature with the [monomer]₀/[initiator]₀ ratio of 50/1 was investigated. The polymerizations homogeneously proceeded to afford poly(ε‐caprolactone) (PCL), poly(1,5‐dioxepan‐2‐one) (PDXO), and polylactide (PLA) with controlled molecular weights and narrow polydispersity indices. The molecular weight determined from an ¹H NMR analysis (PCL, M_n,NMR = 5380; PDXO, M_n,NMR = 5820; PLA, M_n,NMR = 6490) showed good agreement with the calculated values. The ¹H NMR and matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry analyses strongly indicated that the obtained compounds were the desired polyesters. The kinetic measurements confirmed the controlled/living nature for the HNTf₂‐catalyzed ROP of cyclic esters. A series of functional alcohols, such as propargyl alcohol, 6‐azido‐1‐hexanol, N‐(2‐hydroxyethyl)maleimide, 5‐hexen‐1‐ol, and 2‐hydroxyethyl methacrylate, successfully produced end‐functionalized polyesters. In addition, poly(ethylene glycol)‐block‐polyester, poly(δ‐valerolactone)‐block‐poly(ε‐caprolactone), and poly(ε‐caprolactone)‐block‐polylactide were synthesized using the HNTf₂‐catalyzed ROP. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2455–2463     

Polyester from dimethylketene and acetaldehyde: Direct copolymerization and β‐lactone ring‐opening polymerization

Two ways to obtain aliphatic polyesters (PEs) from dimethylketene and acetaldehyde were investigated. On the one hand, a direct anionic copolymerization was carried out in toluene at ?60 °C. The resulting polymer was mainly composed of PE units. On the other hand, a two‐step process involving the synthesis of 3,3,4‐trimethyl‐2‐oxetanone by [2+2] cycloaddition, followed by its ring‐opening polymerization, with various initiators and solvents, led to the expected PE. Molecular weights up to 9000 g mol^?1 (measured by nuclear magnetic resonance (NMR)), with narrow polydispersity around 1.2, were obtained. These polymers were found stable up to 274 °C under nitrogen and a broad and complex endothermic peak attributed to crystallinity was observed near 139 °C by differential scanning calorimetry (DSC). The crystallinity, measured by X‐ray diffraction, was close to 0.45. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Tunable block copolymers based on a polysiloxane backbone by anionic ring‐opening polymerization

Block copolymers with tunable functional groups were obtained through the postfunctionalization of poly(dimethylsiloxane)‐b‐poly(methylvinylsiloxane) diblock copolymers prepared by the anionic ring‐opening polymerization of cyclotrisiloxanes. As the source of the vinyl‐containing segment, 1,3,5‐trimethyl‐1,3,5‐trivinylcyclotrisiloxane was used. The obtained polymers showed high block purity and a narrow molecular weight distribution. The postmodification was carried out with a two‐step procedure: in the first step, epoxide groups were introduced into the diblock copolymer, and in the second step, the ring opening of the latter functionalities was carried out. A variety of different nucleophiles were used for the ring‐opening reaction, and the influence of selected reaction parameters, such as the dilution and the use of monofunctional and difunctional nucleophiles, on the resulting polymers were investigated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3975–3985, 2004     

Synthesis of a new 2‐amino‐glycan,poly‐(1→6)‐α‐D‐mannosamine,by ring‐opening polymerization of 1,6‐anhydro‐mannosamine derivatives

A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative ( 3 ) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative ( 6 ), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (M_n) of 2.3 × 10⁴ to 2.9 × 10⁴ with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D ‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone: Selective formation of polythioester

Cationic ring‐opening polymerization of ϵ‐thionocaprolactone was examined. The corresponding polythioester with the number‐average molecular weight (M_n ) of 57,000 was obtained in the polymerization with 1 mol % of BF₃ · OEt₂ as an initiator in CH₂Cl₂ at 28 °C for 5 h with quantitative monomer conversion. The M_n of the polymer increased with the solvent polarity and monomer‐to‐initiator ratio. No polymerization took place below −30 °C, and the monomer conversion and M_n of the polymer increased with the temperature in the range of −15 to 28 °C. The increase of initial monomer concentration was effective to improve the monomer conversion and the M_n of the obtained polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4057–4061, 2000     

Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and properties of poly(carbonate‐co‐ester)s obtained by cationic ring‐opening copolymerization of spiroorthocarbonate and ε‐caprolactone

Cationic ring‐opening copolymerization behavior of 1,5,7,11‐tetraoxaspiro[5.5]undecane (SOC1) and ε‐caprolactone (CL), and the thermal behavior of the obtained copolymers are described. When SOC1 and CL were cationically copolymerized under various feed ratios using BF₃OEt₂ as the initiator in CH₂Cl₂ at 25 °C, the corresponding copolymers were obtained in 77–99% yields. The ¹H NMR spectroscopic analysis of the copolymers revealed that the copolymer compositions were almost identical to the feed ratios, and the diad ratios of SOC1–SOC1/SOC1–CL and CL–SOC1/CL–CL are 48.0/52.0 and 54.3/45.7. These observations proved the random structures of the copolymers without containing the long blocks of the homopolymer sequences. Differential scanning calorimetric (DSC) analysis revealed that the melting points and melting entharpies decreased with the increase of the SOC1 unit compositions, suggesting that the copolymers gain flexibility as the SOC1 unit increases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2937–2942, 2006     

Cationic ring‐opening polymerization of trimethylene carbonate to α,ω‐dihydroxy telechelic and star‐shaped polycarbonates catalyzed by reusable o‐benzenedisulfonimide

Cationic ring‐opening polymerization of trimethylene carbonate using o‐benzenedisulfonimide as a reusable catalyst under mild conditions was described. The polymerization proceeded homogeneously without decarboxylation and poly(trimethylene carbonates) (PTMCs) were synthesized with well‐controlled molecular weights and narrow polydispersities (M_w/M_n = 1.12–1.18). The spectra of ¹H‐NMR, SEC, and MALDI–ToF MS clearly demonstrated the incorporation of the initiator residue into the polymer chains and the controlled/living nature of the polymerizations. Furthermore, the catalyst can be easily recovered, and its efficiency was fully retained. In addition, 1,3‐propanediol, 1,1,1‐trimethylolpropane, and pentaerythritol were successfully used as initiators to produce telechelic and star‐shaped polycarbonates which were determined by intrinsic viscosity experiments. The number of arms estimated by the shrinking factors ( ) were 2.0, 2.6, and 3.5, respectively, indicating the successful syntheses of the two‐, three‐, and four‐armed PTMCs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 729–736     

Chemistry of 2‐oxazolines: A crossing of cationic ring‐opening polymerization and enzymatic ring‐opening polyaddition

Chemistry of 2‐oxazolines is involved in the polymer synthesis fields of cationic ring‐opening polymerization (CROP) and enzymatic ring‐opening polyaddition (EROPA), although both polymerizations look like a quite different class of reaction. The key for the polymerization to proceed is combination of the catalyst (initiator) and the design of monomers. This article describes recent developments in polymer synthesis via these two kinds of polymerizations to afford various functional polymers having completely different structures, poly(N‐acylethylenimine)s via CROP and 2‐amino‐2‐deoxy sugar unit‐containing oligo and polysaccharides via EROPA, respectively. From the viewpoint of reaction mode, an acid‐catalyzed ring‐opening polyaddition (ROPA) is considered to be a crossing where CROP and EROPA meet. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1251–1270, 2010     

Preparation of functionalized block copolymers based on a polysiloxane backbone by anionic ring‐opening polymerization

Polysiloxane diblock copolymers containing a pure polysiloxane backbone were prepared by the functionalization of poly(dimethylsiloxane)‐b‐poly(methylvinylsiloxane) copolymers. The copolymers were obtained by the sequential anionic copolymerization of either 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetrasiloxane or 1,3,5‐trimethyl‐1,3,5‐trivinylcyclotrisiloxane with hexamethylcyclotrisiloxane. The two vinyl monomers showed large differences in the propagation rates, but both could be used for the formation of polysiloxane block copolymers. Differences in the polymerization sequences were investigated and revealed that better control was obtained if the slower propagating monomer was polymerized first. The method permitted the synthesis of block copolymers with molecular weight distributions around 1.4 and lower and high block purities. The vinyl groups of the block copolymers were quantitatively and selectively functionalized by hydrosilation or epoxidation reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1539–1551, 2002