Using controlled radical polymerization to confirm the lower critical solution temperature of an N‐(alkoxyalkyl) acrylamide polymer in aqueous solution

N‐(3‐Methoxypropyl) acrylamide (MPAM) was polymerized by controlled radical polymerization (CRP) methods such as nitroxide‐mediated polymerization (NMP) and reversible addition–fragmentation chain‐transfer polymerization (RAFT). CRP was expected to yield well‐defined polymers with sharp lower critical solution temperature (LCST) transitions. NMP with the BlocBuilder (2‐([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino]oxy)‐2‐methylpropanoic acid) and SG1 ([tert‐butyl[1‐(diethoxyphosphoryl)‐2,2‐dimethylpropyl]amino] oxidanyl) initiating system revealed low yields and lack of control (high dispersity, ? ～ 1.5–1.6, and inhibition of chain growth). However, RAFT was far more effective, with linear number average molecular weight, , versus conversion, X, plots, low ? ～ 1.2–1.4 and the ability to form block copolymers using N,N‐diethylacrylamide (DEAAM) as the second monomer. Poly(MPAM) (with = 13.7–25.3 kg mol^?1) thermoresponsive behavior in aqueous media revealed cloud point temperatures (CPT)s between 73 and 92 °C depending on solution concentration (ranging from 1 to 3 wt %). The and the molecular weight distribution were the key factors determining the CPT and the sharpness of the response, respectively. Poly(MPAM)‐b‐poly(DEAAM) block copolymer ( = 22.3 kg mol^?1, ? = 1.41, molar composition F_DEAAM = 0.38) revealed dual LCSTs with both segments revealing distinctive CPTs (at 75 and 37 °C for poly(MPAM) and poly(DEAAM) blocks, respectively) by both UV–Vis and dynamic light scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 59–67     

Heterofunctional RAFT‐derived PNIPAM via cascade trithiocarbonate removal and thiol‐yne coupling click reaction

An efficient one‐pot process to functionalize the α‐ and ω‐positions of RAFT‐derived poly(N‐isopropylacrylamide) (PNIPAM) by two inherently different mechanistic pathways is reported. The method relies on the RAFT polymerization of NIPAM using a new alkyne‐based RAFT agent, namely 2‐cyano‐5‐oxo‐5‐(prop‐2‐yn‐1‐ylamino)pentan‐2‐yl dodecyltrithiocarbonate (COPYDC) and the combination of thiol‐yne click chemistry and thiocarbonylthio chain‐end removal reactions. COPYDC was prepared in good yield and used as an efficient chain transfer agent during the RAFT polymerization of NIPAM. Well‐defined polymers with controlled molar masses ( = 7500–14,700 g.mol^?1) and narrow dispersities (? = 1.18–1.26) are thus obtained. Cascade thiol‐yne click reaction at the alkyne α‐chain end and trithiocarbonate removal at the ω‐chain end are successfully achieved using benzyl mercaptan and excess AIBN. The reported method provides a facile and mild route to heterofunctional telechelic RAFT polymers with predictable molar masses and low dispersities. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3597–3606     

Effect of tetra‐n‐butylammonium bromide salt on the cationic polymerization of dimethylketene and on the thermal properties of the obtained polyketones

The cationic polymerization of dimethylketene is achieved in dichloromethane at ?30 °C, using a stoichiometric mixture of aluminum bromide (AlBr₃) and tetra‐n‐butylammonium bromide (n‐Bu₄N⁺Br^?) as initiator. Characterizations by ¹H and ¹³C NMR show that the resulting polymers have a perfect polyketonic microstructure. Capillary viscosity, DSC, and SEC analysis show that for a constant monomer/initiator ratio, polymers synthesized in the presence of tetra‐n‐butylammonium bromide are more crystalline and have better properties than those produced only with AlBr₃. Melting temperatures, inherent viscosities and average molecular weights are systematically higher. A good linearity is observed between ln (inherent viscosity) versus ln for the system with n‐Bu₄N⁺Br^?, showing a good control of the molecular weight by the initial feed ratio. The effect of this compound suggests a reversible equilibrium between active and dormant species, which limits the transfer and/or termination reactions, and enables a better control of the cationic polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1493–1499     

Controlled radical polymerization of styrene mediated by the C‐phenyl‐N‐tert‐butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis

Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10^?10 mol L^?1 at 110 °C. At this temperature, the dissociation rate constant (k_d) is 3.7 × 10^?3 s^?1, the recombination rate constant (k_c) is 4.3 × 10⁶ L mol^?1 s^?1, whereas the activation energy (E_a,diss.), for the dissociation of the alkoxyamine at the chain‐end is ～125 kJ mol^?1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007     

Poly(p‐phenylene methylene)‐based block copolymers by mechanistic transformation

The synthesis of poly(p‐phenylene methylene) (PPM)‐based block copolymers such as poly(p‐phenylene methylene)‐b‐poly(ε‐caprolactone) and poly(p‐phenylene methylene)‐b‐polytetrahydrofuran by mechanistic transformation was described. First, precursor PPM was synthesized by acid‐catalyzed polymerization of tribenzylborate at 16 °C. Then, this polymer was used as macroinitiators in either ring‐opening polymerization of ε‐caprolactone or cationic ring‐opening polymerization of tetrahydrofuran to yield respective block copolymers. The structures of the prepolymer and block copolymers were characterized by GPC and ¹H NMR investigations. The composition of block copolymers as determined by ¹H NMR and TGA analysis was found to be in very good agreement. The thermal behavior and surface morphology of the copolymers were also investigated, respectively, by differential scanning calorimetry and atomic force microscopy measurements, and the contribution of the major soft segment has been observed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Novel pendent thiophene side‐chained benzodithiophene for polymer solar cells

In this article, pendent thiophene (2‐butyl‐5‐octylthiophene) side chain is used to modify the backbone of the polymers containing benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD). Compared with the dodecyloxy side‐chained polymer (P1), pendent thiophene‐based polymers (P2 and P3) show similar number‐average molecular weight (M_n), polydispersity index, thermal stability (T_d ～ 334–337 °C), and optical band gaps ( ) (～1.8 eV). Polymer (P2)‐based BDT with pendent thiophene and ethylhexyl‐modified TPD shows relatively low‐lying HOMO energy level (?5.52 eV) and nearly 1 V high open circuit voltage (V_OC). The polymer solar cell devices based on three copolymers show power conversion efficiencies from 2.01% to 4.13%. The hole mobility of these polymers tested by space charge limited current method range from 3.4 × 10^?4 to 9.2 × 10^?4 cm²V^?1s^?1. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1558–1566     

Photoresponsive polyamides containing pentamethylated norbornadiene moieties: Synthesis and photochemical properties under sunlight irradiation

Photoresponsive polyamides containing main‐chain pentamethylated norbornadiene (NBD) moieties are obtained in quantitative yields via the Yamazaki–Higashi reaction between a pentamethylated NBD dicarboxylic acid and a series of aromatic diamines. Chemical structures are confirmed by ¹H and ¹³C NMR and weight average molar masses measured by SEC are in the range of 21,500–28,600 g mol^?1 with chain dispersities close to 2. Physical properties are investigated by FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis, and viscosimetry. All obtained polyamides are amorphous with glass transition temperatures ranging from 68 to 124 °C. They are soluble at room temperature in common organic solvents and exhibit good thermal stabilities with T_d10 values ranging from 175 to 276 °C. The photochemical isomerization of the NBD moiety into quadricyclane (QC) is studied by UV/vis spectroscopy after sunlight irradiation of polymer films. For all polyamides, a first‐order kinetic rate is observed for the conversion of NBD to QC. The thermal release of the stored energy associated to the reverse transformation of QC groups into NBD ones is about 90–95 kJ mol^?1 as measured by DSC of the irradiated polymer films. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4650–4656     

Synthesis and properties of long‐chain branched poly(ether sulfone)s by self‐polycondensation of AB2 type macromonomers

Long‐chain branched poly(ether sulfone)s (PESs) were synthesized via self‐polycondensation of AB₂ macromonomers. The linear PES oligomers synthesized by self‐polycondensation of 4‐chloro‐4′‐(4‐hydroxyphenyloxy)diphenyl sulfone were terminated with 4‐(3,5‐methoxyphenoxy)‐4′‐fluorodiphenyl sulfone to form AB₂ macromonomer precursors. After conversion from methoxy to hydroxy groups, the AB₂ macromonomers were self‐polycondensed to form long‐chain branched PESs. NMR measurements support the formation of the target macromonomers ( = 2930–67,800 (g mol^?1); M_n = number average molecular weight) and long‐chain branched PESs. Gel permeation chromatography with multiangle light scattering measurements indicated the formation of high‐molecular‐weight (M_w) polymers over 10⁴. The root‐mean‐square radius of gyration (R_g) suggests that the shape of the long‐chain branched PES synthesized from small AB₂ macromonomers in solution is similar to that of hyperbranched polymers. Increasing resulted in larger R_g, suggesting a transition from hyperbranched to a linear‐like architecture in the resulting long‐chain branched PESs. Rheological measurements suggested the presence of strongly entangled chains in the long‐chain branched PES. Higher tensile modulus and smaller elongation at the break were observed in the tensile tests of the long‐chain branched PESs. It is assumed that the enhanced molecular entanglement points may act as physical crosslinks at room temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1825–1831     

Construction of excellent thermal latent system for the synthesis of networked epoxide polymers by sulfonium salts

An efficient thermally latent initiation system using dual sulfonium salts, consisting S‐benzylsulfonium salt 1 bearing counter anion and S,S‐dimethylsulfonium salt 2 bearing CH₃ counter anion, has been developed for the cationic polymerization of epoxides. Compared to the conventional system using 1 as a thermally latent initiator, the newly developed system allowed significant improvement of stability of epoxy formulations during storage at ambient temperature without sacrificing their curability at elevated temperatures. Such a remarkable performance is attributable to the nucleophilic attack of CH₃ to cationic species formed unavoidably by the reaction of 1 with epoxide. Such entrapment of cationic species into the corresponding dormant led to the inhibition of undesirable chain growth of polymers during storage of epoxy formulations. In addition, the dormant can undergo dissociation at elevated temperature to give cationic species, which can readily initiate the polymerization of epoxide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2096–2102     

Polyisobutylene containing covalently bound antioxidant moieties

Polyisobutylene (PIB) bearing covalently bound antioxidants is reported. TiCl₄‐catalyzed cleavage/alkylation reactions were conducted on poly(isobutylene‐co‐isoprene) (EXXON® Butyl 068; ${\overline{\mathrm{M}}}_{\mathrm{n}}$ = 3.37 × 10⁵ g/mol, (Ð) = 1.29, and 1.08 mol % isoprene) at ?70 °C in 60/40 hexane/dichloromethane in the presence of 2,6‐di‐tert‐butylphenol (DTP). Resulting PIB ${\overline{\mathrm{M}}}_{\mathrm{n}}$ s ranged from 30,000 to 85,300 g/mol and number average DTP functionalities (F_n) ranged from 4.3 to 12.0. ¹H NMR showed that 25%–40% of the DTP moieties underwent de‐tert‐butylation to form mono‐tert‐butyl phenol moieties. DTP‐functionalized and nonfunctionalized control PIBs were subjected to thermogravimetric analysis in nitrogen and in air. In nitrogen, commercial control PIBs (olefinic end groups) showed delayed onset of thermal degradation (T₁₀ = 380–381 °C) relative to both control PIBs produced by living polymerization (tert‐chloride end groups) and DTP‐functionalized PIBs (T₁₀'s all within the range of 366–370 °C). All PIBs showed lower degradation temperatures in air compared to nitrogen. Various control PIBs suffered 90% weight loss in air at temperatures ranging from 372 °C to 410 °C; DTP‐functionalized PIBs did not suffer 90% weight loss in air until 412–414 °C. Oxidative induction time analysis showed that all control PIBs suffered catastrophic degradation within 6 min, and most within 1 min, but DTP‐functionalized PIBs resisted degradation for >100 min. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1836–1846     

Combination of nitroxide‐mediated polymerization and SET‐LRP for the synthesis of high molar mass branched and star‐branched poly(n‐butyl acrylate) characterized by size exclusion chromatography and rheology

Branched and star‐branched polymers were successfully synthesized by the combination of two successive controlled radical polymerization methods. A series of linear and star poly(n‐butyl acrylate)‐co‐poly(2‐(2‐bromoisobutyryloxy) ethyl acrylate) statistical copolymers, P(nBA‐co‐BIEA)_x, were first synthesized by nitroxide‐mediated polymerization (NMP at T > 100 °C). The subsequent polymerization of n‐butyl acrylate by single electron transfer‐living radical polymerization (SET‐LRP at T = 25 °C), initiated from the brominated sites of the P(nBA‐co‐BIEA)_x copolymer, produced branched or star‐branched poly(n‐butyl acrylate) (PnBA). Both types of polymerizations (NMP and SET‐LRP) exhibited features of a controlled polymerization with linear evolutions of logarithmic conversion versus time and number‐average molar masses versus conversion for final M_n superior to 80,000 g mol^?1. The branched and star‐branched architectures with high molar mass and low number of branches were fully characterized by size exclusion chromatography. The Mark–Houwink Sakurada relationship and the analysis of the contraction factor (g′ = ([η]_branched/[η]_linear)_M) confirmed the elaboration of complex PnBA. The zero‐shear viscosities of the linear, star‐shaped, branched, and star‐branched polymers were compared. The modeling of the rheological properties confirmed the synthesis of the branched architectures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Microwave‐assisted ring‐opening polymerization of p‐dioxanone

The ring‐opening polymerization (ROP) of p‐dioxanone (PDO) under microwave irradiation with triethylaluminum (AlEt₃) or tin powder as catalyst was investigated. When the ROP of PDO was catalyzed by AlEt₃, the viscosity‐average molecular weight (M_v) of poly(p‐dioxanone) (PPDO) reached 317,000 g mol^?1 only in 30 min, and the yield of PPDO achieved 96.0% at 80 °C. Tin powder was successfully used as catalyst for synthesizing PPDO by microwave heating, and PPDO with M_v of 106,000 g mol^?1 was obtained at 100 °C in 210 min. Microwave heating accelerated the ROP of PDO catalyzed by AlEt₃ or tin powder, compared with the conventional heating method. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3207–3213, 2008     

Controlled synthesis of poly(dimethylsiloxane) homopolymers using high‐vacuum anionic polymerization techniques

The controlled synthesis of poly(dimethylsiloxane) homopolymers (PDMS) using hexamethyl(cyclotrisiloxane) monomer (D₃), a mixture of ciclohexane/tetrahydrofuran 50/50 v/v and sec‐Bu^–Li⁺ as initiator was studied using different experimental conditions, and whole‐sealed glass reactors according to standards procedures in high‐vacuum anionic polymerization. It was observed that polydispersity indexes (PD) and conversions strongly depend on temperature and reaction times. For PDMS homopolymers with molar masses below 100,000 g/mol, high conversion (>90%) and PD < 1.1 can be achieved at long reaction times (24 h) and mild temperature conditions (below or up to 30 °C). On the other hand, to synthesize PDMS homopolymers with molar masses higher than 100,000 g/mol and PD < 1.1 it is necessary to increase the temperature up to 50 °C and decrease the reaction time (8 h). However, under these reaction conditions, it was observed that the conversion decreases (about 65–70% conversion is achieved). Apparently, the competition between propagation and secondary reactions (redistribution, backbiting, and reshuffling) depends on the molar masses desired. According to the results obtained in this study—which were compared with others found in the scientific literature—propagation is favored when M_n < 100,000 g/mol, whereas secondary reactions seem to become important for higher molar masses. Nevertheless, model PDMS homopolymers with high molar masses can still be obtained increasing the reaction temperature and shortening the total reaction time. It seems that the combined effect of these two facts favors propagation against secondary reactions, and provides model PDMS homopolymers with molar masses quite close to the expected ones. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4774–4783, 2009     

Cationic polymerization of vinyl ethers with alkyl or ionic side groups in ionic liquids

Controlled cationic polymerization of isobutyl vinyl ether was demonstrated to proceed in an ionic liquid (IL), 1‐butyl‐3‐octylimidazolium bis(trifluoromethanesulfonyl)imide, using a 1‐(isobutoxy)ethyl acetate/TiCl₄ initiating system, ethyl acetate as an added base, and 2,6‐di‐tert‐butylpyridine as a proton trap reagent. Judicious choices of metal halide catalysts, counteranions of ILs, and additives were essential for controlling the polymerization. The polymerization proceeded much faster in the IL than in CH₂Cl₂, indicating an increased population of ionic active species in the IL due to the high polarity. Polymers with a relatively narrow molecular weight distribution were obtained in the IL with a bis(trifluoromethanesulfonyl)imide ( ) anion even in the absence of an added base, which suggested possible interactions of the counteranion of the IL with the growing carbocations. Moreover, the direct cationic polymerization of a vinyl ether with pendant imidazolium salts, 1‐(2‐vinyloxyethyl)‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide, proceeded in a homogeneous state in 1‐methyl‐3‐octylimidazolium bis(trifluoromethanesulfonyl)imide. The solubilities of the obtained polymers were readily tuned by counteranion exchange. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1774–1784     

Semicontinuous heterophase polymerization under monomer starved conditions to prepare nanoparticles with narrow size distribution

The semicontinuous polymerization of methyl methacrylate (MMA) in heterogeneous medium under monomer‐starved conditions is reported here. The effect of monomer addition rate on kinetics, particle size, particle number, and PMMA average molar masses are reported. This process permits the synthesis of high‐solid content latexes containing nano‐sized particles (<40 nm) with narrow particle size distributions [(D_w/D_n) < 1.1]. Moreover, the molar masses (M_n ≈ 0.3–1.2 × 10⁶ g/mol) are much lower than those expected by chain transfer to monomer, which is the typical termination mechanism in 0–1 emulsion and microemulsion reactions. Both particle size and average molar masses decrease as the rate of monomer addition is diminished. Possible explanations for this process are provided. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1463–1473, 2007     

A minimal amount of acrylonitrile turns the nitroxide‐mediated polymerization of methyl methacrylate into an almost ideal controlled/living system

Nitroxide‐mediated controlled/living free‐radical polymerization of methyl methacrylate initiated by the SG1‐based alkoxyamine BlocBuilder was successfully performed in bulk at 80–99 °C with the help of a very small amount of acrylonitrile (AN, 2.2–8.8 mol %) as a comonomer. Well‐defined PMMA‐rich P(MMA‐co‐AN) copolymers were prepared with the number‐average molar mass, M_n, in the 6.1–32 kg mol^?1 range and polydispersity indexes as low as 1.24. Incorporation of AN in the copolymers was demonstrated by ¹H and ¹³C NMR spectroscopy, and its effect on the chain thermal properties was evaluated by DSC and TGA analyses. Investigation of chain‐end functionalization by an alkoxyamine group was performed by means of ³¹P NMR spectroscopy and chain extensions from a P(MMA‐co‐AN)‐SG1 macroinitiator. It demonstrated the very high proportion of SG1‐terminated polymer chains, which opened the door to block copolymer synthesis with a high quality of control. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 34–47, 2010     

Radical polymerization of vinyl thiocyanatoacetate: Participation of group‐transfer mechanism

Vinyl thiocyanatoacetate (VTCA) was synthesized, and its radical polymerization behavior was studied in acetone with dimethyl 2,2′‐azobisisobutyrate (MAIB) as an initiator. The initial polymerization rate (R_p) at 60 °C was expressed by R_p = k[MAIB]^0.6±0.1 [VTCA]^1.0±0.1 where k is a rate constant. The overall activation energy of the polymerization was 112 kJ/mol. The number‐average molecular weights of the resulting poly (VTCA)s (1.4–1.6 × 10⁴) were almost independent of the concentrations of the initiator and monomer, indicating chain transfer to the monomer. The chain‐transfer constant to the monomer was estimated to be 9.6 × 10^?3 at 60 °C. According to the ¹H and ¹³C NMR spectra of poly (VTCA), the radical polymerization of VTCA proceeded through normal vinyl addition and intramolecular transfer of the cyano group. The cyano group transfer became progressively more important with decreasing monomer concentration. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 573–582, 2002; DOI 10.1002/pola.10137     

Catalytic chain transfer polymerization of isobutylene: The role of nucleophilic impurities

Fast polymerization of isobutylene (IB) initiated by tert‐butyl chloride using ethylaluminum dichloride·bis(2‐chloroethyl) ether complex (T. Rajasekhar, J. Emert, R. Faust, Polym. Chem. 2017, 8, 2852) was drastically slowed down in the presence of impurities, such as propionic acid, acetone, methanol, and acetonitrile. The effect of impurities on the polymerization rate was neutralized by using two different approaches. First, addition of a small amount of iron trichloride (FeCl₃) scavenged the impurity and formed an insoluble · impurity complex in hexanes. The polymerization rate and exo‐olefin content were virtually identical to that obtained in the absence of impurities. Heterogeneous phase scavenger (FeCl₃) exhibited better performance than homogenous phase scavengers. In the second approach, conducting the polymerization in wet hexanes, the fast polymerization of IB was retained in the presence of impurities with a slight decrease in exo‐olefin content. ¹H NMR studies suggest that nucleophilic impurities are protonated in the presence of water, and thereby neutralized. Mechanistic studies suggest that the rate constant of activation (k_a), rate constant of propagation (k_p), and rate constant of β‐proton elimination (k_tr) are not affected by the presence of impurities. To account for the retardation of polymerization in the presence of impurities, delay of proton transfer to monomer in the chain transfer step is proposed. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3697–3704     

Vinyl addition polymerization of norbornene using cyclopentadienylzirconium trichloride activated by isobutyl‐modified methylaluminoxane

Norbornene polymerization using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl₃) and isobutyl‐modified methylaluminoxane (MMAO), were carried out over a wide range of polymerization temperatures and monomer concentrations. For the CpZrCl₃ catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO_40/60), the polymerization temperature and monomer concentration significantly affected the molecular weight (M_n) of the obtained polymer and the catalytic activity. With an increase in the polymerization temperature from 0 to 27 °C, the catalytic activity and M_n increased, but these values dramatically decreased with the increasing polymerization temperature from 27 to 70 °C, meaning that the most suitable temperature was 27 °C. The CpZrCl₃/MMAO_40/60 ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.76 mol L^?1 at 27 °C showed the highest activity of 145 kg mol_Zr^?1 h^?1 and molecular weight of 211,000 g mol^?1. The polymerization using the CpZrCl₃/MMAO_40/60 catalyst system proceeds through the vinyl addition mechanism to produce atactic polynorbornene, which was soluble in chloroform, toluene, and 1,2‐dichlorobenzene, but insoluble in methanol. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1185–1191, 2008     

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