A new approach to control crystallinity of resulting polymers: Self‐condensing ring opening polymerization

The cationic polymerization of 3‐methyl‐3‐oxetanemethanol was initiated using BF₃·OEt₂. The low ratio of catalyst to monomer results in a mainly linear or slightly branched polymer, and the high catalyst to monomer ratio leads to a hyperbranched polymer. The hyperbranched polyether yielded is amorphous, and the essentially linear version obtained is partially crystalline. In other words, the degree of branching and the crystallinity of resulting polymers are dependent on the catalyst to monomer ratio. Therefore a new approach to control the crystallinity of resulting polymers in self‐condensing ring opening polymerization was developed.     

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 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 comb‐shaped poly(methyl methacrylate)‐b‐poly(polytetrahydrofuran acrylate) under 60Co γ‐ray irradiation

Comb‐shaped graft copolymers with poly(methyl methacrylate) as a handle were synthesized by the macromonomer technique in two steps. First, polytetrahydrofuran acrylate (A‐PTHF), prepared by the living cationic ring‐opening polymerization of tetrahydrofuran, underwent homopolymerization with 1‐(ethoxycarbonyl)prop‐1‐yl dithiobenzoate as an initiator under ⁶⁰Co γ irradiation at room temperature; Second, the handle of the comb‐shaped copolymers was prepared by the block copolymerization of methyl methacrylate with P(A‐PTHF) as a macroinitiator under ⁶⁰Co γ irradiation. The two‐step polymerizations were proved to be controlled with the following evidence: the straight line of ln[M]₀/[M] versus the polymerization time, the linear increase in the number‐average molecular weight with the conversion, and the relatively narrow molecular weight distribution. The structures of the P(A‐PTHF) and final comb‐shaped copolymers were characterized by ¹H NMR spectroscopy and gel permeation chromatography. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3367–3378, 2002     

Cationic ring‐opening polymerization of monothiocarbonate with a norbornene group

This work deals with the cationic ring‐opening polymerization of cyclic thiocarbonates with a norbornene or norbornane moiety, that is, 5,5‐(bicyclo[2.2.1]hept‐2‐ene‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC1 ) or 5,5‐(bicyclo[2.2.1]heptane‐5,5‐ylidene)‐1,3‐dioxane‐2‐thione ( TC2 ), respectively. The reaction of TC1 initiated by trifluoromethanesulfonic acid (TfOH), methyl trifluoromethanesulfonate (TfOMe), boron trifluoride etherate (BF₃OEt₂), or triethyloxonium tetrafluoroborate (Et₃OBF₄) afforded unidentified products; however, TC1 underwent cationic ring‐opening polymerization with methyl iodide as an initiator to afford polythiocarbonate because the propagating end was stabilized by the covalent‐bonding property. The polymerization of TC2 initiated by TfOH, TfOMe, BF₃OEt₂, or Et₃OBF₄ afforded polythiocarbonate with good solubility in common organic solvents and a narrow molecular weight distribution because of the absence of a double‐bond moiety. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1698–1705, 2002     

Synthesis of poly(β‐pinene)‐g‐poly(meth)acrylate by the combination of living cationic polymerization and atom transfer radical polymerization

New graft copolymers of β‐pinene with methyl methacrylate (MMA) or butyl acrylate (BA) were synthesized by the combination of living cationic polymerization and atom transfer radical polymerization (ATRP). β‐Pinene polymers with predetermined molecular weights and narrow molecular weight distributions (MWDs) were prepared by living cationic polymerization with the 1‐phenylethyl chloride/TiCl₄/Ti(OiPr)₄/nBu₄NCl initiating system, and the resultant polymers were brominated quantitatively by N‐bromosuccinamide in the presence of azobisisobutyronitrile, yielding poly(β‐pinene) macroinitiators with different bromine contents (Br/β‐pinene unit molar ratio = 1.0 and 0.5 for macroinitiators a and b , respectively). The macroinitiators, in conjunction with CuBr and 2,2′‐bipyridine, were used to initiate ATRP of BA or MMA. With macroinitiator a or b , the bulk polymerization of BA induced a linear first‐order kinetic plot and gave graft copolymers with controlled molecular weights and MWDs; this indicated the living nature of these polymerizations. The bulk polymerization of MMA initiated with macroinitiator a was completed instantaneously and induced insoluble gel products. However, the controlled polymerization of MMA was achieved with macroinitiator b in toluene and resulted in the desired graft copolymers with controlled molecular weights and MWDs. The structures of the obtained graft copolymers of β‐pinene with (methyl)methacrylate were confirmed by ¹H NMR spectra. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1237–1242, 2003     

Synthesis and characterization of degradable hyperbranched poly(2‐ethyl‐2‐oxazoline)

Hyperbranched poly(2‐ethyl‐2‐oxazoline) was synthesized by a combination of cationic ring‐opening polymerization and the oxidation of thiol to disulfide groups. A three‐arm star poly(2‐ethyl‐2‐oxazoline) (PEtOx) was first synthesized using 1,3,5‐tris(bromomethyl) benzene as an initiator. The star PEtOx was end‐capped with potassium ethyl xanthate. Similarly, a linear PEtOx was synthesized and end‐capped with potassium ethyl xanthate using benzyl bromide as an initiator. Hyperbranched PEtOx was then obtained by in situ cleaving and subsequent oxidation of the star PEtOx and linear PEtOx mixture with n‐butylamine as both a cleaving agent and a base in tetrahydrofuran. The linear PEtOx was used to prevent the formation of gel. The hyperbranched PEtOx can be cleaved with dithiothreitol to trithiol and monothiol polymer. The hyperbranched PEtOx shows no remaining thiols using Ellman's assay. The resulting hyperbranched PEtOx was hydrolyzed to a novel hyperbranched polyethyleneimine with degradable disulfide linkages. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2030–2037     

Regio‐ and stereoselective cyclopolymerization of 1,2 : 4,5‐dianhydro‐3‐O‐methyl‐xylitol leading to a novel polycarbohydrate of (2→5)‐1,4‐anhydro‐3‐O‐methyl‐pentitol

(2→5)‐1,4‐Anhydro‐3‐O‐methyl‐pentitol, which is a novel carbohydrate polymer without an anomeric linkage, was synthesized by cationic cyclopolymerization of 1,2 : 4,5‐dianhydro‐3‐O‐methyl‐xylitol. When BF₃·OEt₂ was used as the initiator, soluble polymers were obtained in 28 to 50% yield. These polymers have number‐average molecular weights of 1 150 to 2 340 corresponding to an average degree of polymerization of 8.8 to 18.0. It was confirmed by ¹³C NMR that the resulting polymer mainly consists of 1,4‐anhydro‐3‐O‐methyl‐D L ‐arabinitol units.     

Cationic ring‐opening polymerization behavior of a five‐membered cyclic thiocarbonate having a spiro‐linked adamantane moiety

This work deals with the synthesis and cationic ring‐opening polymerization behavior of a novel five‐membered cyclic thiocarbonate bearing a spiro‐linked adamantane moiety, tricyclo[3.3.1.1^3,7]decane‐2‐spiro‐4′‐(1′,3′‐dioxolane‐2′‐thione) ( TC2 ). The cationic ring‐opening polymerization of TC2 did not proceed with trifluoromethanesulfonic acid, methyl trifluoromethanesulfonate, triethyloxonium tetrafluoroborate (Et₃OBF₄), boron trifluoride etherate (BF₃OEt₂), titanium tetrachloride, or methyl iodide as the initiator, presumably because of the steric hindrance of the adamantane moiety. However, the cationic ring‐opening copolymerization of TC2 with five‐ or six‐membered cyclic thiocarbonates, that is, 1,3‐dioxolane‐2‐thione, 1,3‐dioxane‐2‐thione, 5‐methyl‐1,3‐dioxane‐2‐thione, or 5,5‐dimethyl‐1,3‐dioxane‐2‐thione, initiated by BF₃OEt₂ or Et₃OBF₄, proceeded to afford the corresponding copolymer via a selective ring‐opening direction. The increase in the feed ratio of TC2 in the copolymerization increased the unit ratio derived from TC2 in the copolymer; however, the molecular weight of the copolymer decreased. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 699–707, 2003     

Association of hydrophobically α,ω‐end‐capped poly(2‐methyl‐2‐oxazoline) in water

The α,ω‐end‐capped poly(2‐methyl‐2‐oxazoline) (C_n‐POXZ‐C_n) have been synthesized by a one‐pot process using cationic ring‐opening polymerization with an appropriate initiator and terminating agent. The polymers bearing different alkyl groups C₁₂ and C₁₈ have molecular weight in the range of 2.4 × 10³ to 14 × 10³ with a small polydispersity index. The solution behavior of the free chains has been analyzed in a nonselective solvent, dichloromethane, by small‐angle neutron scattering and dynamic light scattering. These amphiphilic polymers associate in water to form flower‐like micellar structures. Critical micelle concentrations, investigated by fluorescence technique, are in the range of 0.03–0.5 g L^?1 and are dependent on the hydrophilic/lipophilic balance. The structural properties of the aggregates have also been investigated by viscometry. Intrinsic viscosities of these polymers are in the same range as that of the precursors poly(2‐methyl‐2‐oxazoline) (POXZ) and mono‐functionalized polymers. Large viscosity increase corresponding to intermicellar bridging was observed in the vicinity of the micelle overlap concentration. Addition of hydroxypropyl β‐cyclodextrin (HβCD) has dissociated the aggregates and the intrinsic viscosities of the HβCD‐end‐capped chains have become comparable with the ones of POXZ precursor chains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2477–2485, 2010     

Synthesis,Characterization and Optical Properties of a Novel Si‐Containing σ‐π‐Conjugated Hyperbranched Polymer

The polymerization of bis(4‐ethynylphenyl)methylsilane catalyzed by RhI(PPh₃)₃ afforded a regio‐ and stereoregular hyperbranched polymer, hb‐poly[(methylsilylene)bis(1,4‐phenylene‐trans‐vinylene)] (poly( 1 )), containing 95% trans‐vinylene moieties. The weight loss of this polymer at 900°C in N₂ was 9%. Poly( 1 ) displayed an absorption due to π‐π* transition around 275 nm as a shoulder and a weak absorption around 330 nm due to π‐to‐σ charge transfer, which was hardly seen in the corresponding linear polymer.     

Near‐monodisperse α‐hydroxy and α,ω‐dihydroxy amine‐based polymers: Synthesis and characterization

α‐Hydroxy and α,ω‐dihydroxy polymers of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) of various molecular weights were synthesized by group transfer polymerization (GTP) in tetrahydrofuran (THF), using 1‐methoxy‐1‐(trimethylsiloxy)‐2‐methyl propene (MTS) as the initiator and tetrabutylammonium bibenzoate (TBABB) as the catalyst. The hydroxyl groups were introduced by adding one 2‐(trimethylsiloxy) ethyl methacrylate (TMSEMA) unit at one or at both ends of the polymer chain. The ends were converted to 2‐hydroxyethyl methacrylate (HEMA) units after the polymerization by acid‐catalyzed hydrolysis. Gel permeation chromatography (GPC) in THF and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy in CDCl₃ were used to determine the molecular weight and composition of the polymers. These mono‐ and difunctional methacrylate polymers can be covalently linked at the hydroxy termini to form star polymers and model networks, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1597–1607, 1999     

Synthesis of polyallene‐based graft copolymer via 6‐methyl‐1,2‐heptadien‐4‐ol and styrene

A series of well‐defined graft copolymers with a polyallene‐based backbone and polystyrene side chains were synthesized by the combination of living coordination polymerization of 6‐methyl‐1,2‐heptadien‐4‐ol and atom transfer radical polymerization (ATRP) of styrene. Poly(alcohol) with polyallene repeating units were prepared via 6‐methyl‐1,2‐heptadien‐4‐ol by living coordination polymerization initiated by [(η³‐allyl)NiOCOCF₃]₂ firstly, followed by transforming the pendant hydroxyl groups into halogen‐containing ATRP initiation groups. Grafting‐from route was employed in the following step for the synthesis of the well‐defined graft copolymer: polystyrene was grafted to the backbone via ATRP of styrene. The cleaved polystyrene side chains show a narrow molecular weight distribution (M_w/M_n = 1.06). This kind of graft copolymer is the first example of graft copolymer via allene derivative and styrenic monomer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5509–5517, 2007     

Anionic and ionic coordinative polymerization of ϵ‐caprolactone

The polymerization of ?‐caprolactone initiated by two catalyst systems was studied: (1) carbazole‐potassium in the presence of 18‐crown‐6 ether and (2) NdCl₃/TBP/TIBA (neodymiumtrichloride/tri‐n‐butyl‐phosphate/triisobutylaluminium) at the molar ratio 1/3/1. For both initiator systems conversion/time plots were determined and the polymers were characterized by IR, GPC and by ¹H‐ and ¹³C?NMR spectroscopy. Polyesters with the highest molecular weight (M _n?44 000 g/mol) were obtained for the polymerizations initiated by the carbazole‐potassium/18‐crown‐6 ether system. The features of the polymerization initiated by the carbazole‐potassium/18‐crown‐6 ether system are discussed on the basis of a simple scheme. The nature of this polymerization is non‐living. Copyright © 2000 John Wiley & Sons, Ltd.     

Catalytic effect of dimethyl sulfoxide in the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical polymerization of methyl methacrylate at 0–90 °C initiated with CH3CHClI as a model compound for α,ω‐di(iodo)poly(vinyl chloride) chain ends

A variety of conditions, including catalysts [CuCl, CuI, Cu₂O, and Cu(0)], ligands [2,2′‐bipyridine (bpy), tris(2‐dimethylaminoethyl)amine (Me₆‐TREN), polyethyleneimine, and hexamethyl triethylenetetramine], initiators [CH₃CHClI, CH₂I₂, CHI₃, and F(CF₂)₈I], solvents [diphenyl ether, toluene, tetrahydrofuran, dimethyl sulfoxide (DMSO), dimethylformamide, ethylene carbonate, dimethylacetamide, and cyclohexanone], and temperatures [90, 25, and 0 °C] were studied to assess previous methods for poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) synthesis by the living radical block copolymerization of methyl methacrylate (MMA) initiated with α,ω‐di(iodo)poly(vinyl chloride). CH₃CHClI was used as a model for α,ω‐di(iodo)poly(vinyl chloride) employed as a macroinitiator in the living radical block copolymerization of MMA. Two groups of methods evolved. The first involved CuCl/bpy or Me₆‐TREN at 90 °C, whereas the second involved Cu(0)/Me₆‐TREN in DMSO at 25 or 0 °C. Related ligands were used in both methods. The highest initiator efficiency and rate of polymerization were obtained with Cu(0)/Me₆‐TREN in DMSO at 25 °C. This demonstrated that the ultrafast block copolymerization reported previously is the most efficient with respect to the rate of polymerization and precision of the PMMA‐b‐PVC‐b‐PMMA architecture. Moreover, Cu(0)/Me₆‐TREN‐catalyzed polymerization exhibits an external first order of reaction in DMSO, and so this solvent has a catalytic effect in this living radical polymerization (LRP). This polymerization can be performed between 90 and 0 °C and provides access to controlled poly(methyl methacrylate) tacticity by LRP and block copolymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1935–1947, 2005     

Selectivity in anionic and cationic ring‐opening polymerizations of tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane

Anionic and cationic ring‐opening polymerizations of two novel cyclotrisiloxanes, tetramethyl‐1‐(3′‐trifluoromethylphenyl)‐1‐phenylcyclotrisiloxane ( I ) and tetramethyl‐1‐[3′,5′‐bis(trifluoromethyl)phenyl]‐1‐phenylcyclotrisiloxane ( II ), are reported. Anionic ring‐opening polymerization of I or II leads to copolymers with highly regular microstructures. Copolymers obtained by cationic polymerizations of I or II , initiated by triflic acid, have less regular microstructures characteristic of chemoselective polymerization processes. The composition and microstructure of copolymers have been characterized by ¹H and ²⁹Si‐NMR, the molecular weight distributions by GPC, and the thermal properties by DSC and TGA. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5235–5243, 2004     

Syntheses of trimethoxysilyl‐endcapped polylactones via 3‐mercaptopropyl trimethoxysilane

Monofunctional polylactones were prepared by Bu₂Sn(OMe)₂‐initiated ring‐opening polymerization of ε‐caprolactone (εCL) followed by acylation with bromoacetylbromide. Telechelic polylactones and polylactides were prepared via ring‐expansion polymerization with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP) or 2,2‐dibutyl‐2‐stanna‐pentaoxacyclotridecane (Bu₂SnTEG) as cyclic initiator. In situ combination of the polymerization with condensation by means of bromoacetylbromide yielded polylactones having bromoacetate endgroups. These endgroups were subjected to nucleophilic substitution with 3‐mercaptopropyl trimethoxysilane (3‐MPTMS). Analogous experiments were conducted with dl‐lactide. The telechelic trimethoxysilyl‐endcapped polylactones were characterized by viscosity, ¹H and ¹³C NMR‐spectroscopy, and MALDI‐TOF mass spectrometry. The mass spectra revealed small amounts of cyclic oligolactones as byproducts in all samples. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3667–3674, 2005     

Oxidation polymerization of a charge‐transfer complex of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene with 7,7,8,8‐tetracyanoquinodimethane

A π‐conjugated poly(α‐dithienylen‐dithiafulvene) ( 2 ) was obtained by the oxidation polymerization of 2,6‐bis(2‐thienyl)‐1,4‐dithiafulvene ( 1 ) as a dithiafulvene monomer derived from 4‐(2‐thienyl)‐1,2,3‐thiadiazole. When a solution of 1 in CHCl₃ was added to a stirred solution of FeCl₃ in CHCl₃, only the low‐molecular‐weight product 2 was obtained. The mixture was stirred for 15 h with an N₂ flow. The polymerization at higher temperatures resulted in polymers with large insoluble fractions. A higher molecular weight polymer was obtained by the oxidation polymerization of a charge‐transfer complex of 1 with 7,7,8,8‐tetracyanoquinodimethane (compound 3 ). In contrast to 2 , polymer 4 was readily soluble in dimethyl sulfoxide, dimethylformamide, and acetone and partially soluble in tetrahydrofuran and methanol and had a larger molecular weight (peak top molecular weight = 37,000). The conductivity of polymer 4 was 3 orders of magnitude larger than that of polymer 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6592–6598, 2005     

Radical and cationic polymerizations of 3‐ethyl‐3‐methacryloyloxymethyloxetane

3‐Ethyl‐3‐methacryloyloxymethyloxetane (EMO) was easily polymerized by dimethyl 2,2′‐azobisisobutyrate (MAIB) as the radical initiator through the opening of the vinyl group. The initial polymerization rate (R_p) at 50 °C in benzene was given by R_p = k[MAIB]^0.55 [EMO]^1.2. The overall activation energy of the polymerization was estimated to be 87 kJ/mol. The number‐average molecular weight (M?_n) of the resulting poly(EMO)s was in the range of 1–3.3 × 10⁵. The polymerization system was found to involve electron spin resonance (ESR) observable propagating poly(EMO) radicals under practical polymerization conditions. ESR‐determined rate constants of propagation (k_p) and termination (k_t) at 60 °C are 120 and 2.41 × 10⁵ L/mol s, respectively—much lower than those of the usual methacrylate esters such as methyl methacrylate and glycidyl methacrylate. The radical copolymerization of EMO (M₁) with styrene (M₂) at 60 °C gave the following copolymerization parameters: r₁ = 0.53, r₂ = 0.43, Q₁ = 0.87, and e₁ = +0.42. EMO was also observed to be polymerized by BF₃OEt₂ as the cationic initiator through the opening of the oxetane ring. The M?_n of the resulting polymer was in the range of 650–3100. The cationic polymerization of radically formed poly(EMO) provided a crosslinked polymer showing distinguishably different thermal behaviors from those of the radical and cationic poly(EMO)s. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1269–1279, 2001     

Homopolymerization of cyclic esters initiated by lanthanide isopropoxides supported by 2,2′‐ethylene‐bis(4,6‐di‐tert‐butylphenolate) ligands

Lanthanide isopropoxides supported by carbon‐bridged bisphenolate ligands of 2,2′‐ethylene‐bis(4,6‐di‐tert‐butylphenoxo) {[(EDBP)Ln(μ‐OPrⁱ)(THF)₂]₂, where Ln is Nd ( 1 ), Sm ( 2 ), or Yb ( 3 ) and THF is tetrahydrofuran} were synthesized by protic exchange reactions in high yields with Cp₃Ln compounds as raw materials, and complex 1 was structurally characterized. Complexes 1 – 3 were shown to be efficient initiators for the ring‐opening polymerization of ε‐caprolactone (ε‐CL) and 2,2‐dimethyltrimethylene carbonate (DTC). Complexes 1 – 3 could initiate the controlled polymerization of ε‐CL, and the polymerization rate was first‐order with respect to the monomer. The influence of the reaction conditions on the monomer conversion, molecular weight, and molecular weight distribution of the resultant polymers was investigated. End‐group analyses of the oligomers of ε‐CL and DTC showed that the polymerization underwent a coordination–insertion mechanism. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4409–4419, 2006