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The H-bond and ionic bond of the well-defined PSMA hydrolysates induce the TSI-n–π of carbonyl clusters to emit fluorescence and RTP.

This work discloses a zwitterionic approach for selective copolymerization of carbon dioxide (CO₂) and propylene oxide (PO), producing poly(propylene carbonate) (PPC), a biodegradable polymer with broad applications. Small-molecule catalysts composed of triethylamine (TEA) and trialkyl boranes are effective for CO₂/PO copolymerization with an alternating degree of >99% and a productivity of 171 g PPC/g catalyst. A diamine N,N,N′,N′-tetraethyl ethylenediamine (TEED) paired with trialkyl borane exhibited improved activity and productivity (up to 216 g PPC/g catalyst). By adjusting the Lewis acid–base pair, the PPC selectivity can be regulated to 99%. In addition, PPCs have medium regioregularity with a head-to-tail diad content of 80–82% and number-average molecular weights of up to 56.0 kg/mol with narrow polydispersity (below 1.2). The overall catalytic performance of these readily available simple molecules is better than that of previously reported organic catalysts for CO₂/PO copolymerization. Successive insertion of PO and CO₂ into the Lewis pair leads to the formation of an end-to-end zwitterion featuring a TEB-masked anion and an onium cation, which is highly selective to the alternating copolymerization, as demonstrated by quantum mechanical calculations.

Utilization of carbon disulfide (CS2), a low-cost and sulfur-rich one-carbon (C1) feedstock, for making sulfur-containing polymers is important for both polymer chemistry and applied environmental ...

This work describes the first example of semicrystalline poly(thiocarbonate)s from carbon disulfide (CS2 ) and ethylene oxide (EO), two mass producible low-cost monomers. Lewis acid/base pairs (LPs) exhibit high activity (EO conversion up to >99%, 8 h) in catalyzing the copolymerization under low Lewis pair/monomer ratio of 1:1500. Oxygen-sulfur exchange reaction (O-S ER) during the copolymerization of CS2 and EO, the generation and mutual copolymerization with COS, CO2 , and episulfide, is harnessed to introduce crystallizable segments [SC(O)O and SC(S)S] in the copolymer. The type of Lewis base is found to have a great impact on the chain microstructure and the crystalline properties. The formed copolymers with melting point from 117.7 to 245.3 °C are obtained. The maximum crystallinity is estimated to be 78% based on the powder wide-angle X-ray diffraction pattern. This work provides a general method to prepare semicrystalline sulfur-containing polymers.

The synthesis of high-molecular-weight poly(e-caprolactone)s (PCLs) with enhanced mechanical properties remains challenging. Here we demonstrate the heterogeneous catalysis for the ring-opening polymerization (ROP) of e-caprolactone (e-CL). Using a zinc-cobalt double-metal cyanide complex [Zn-Co(III) DMCC] in the presence of around 1% mol epoxides, PCLs are achieved with high number-average molecular weights (Mns) of up to 177.7 kDa determined by the gel permeation chromatography. The [Zn]-OH active site of the complex triggers the cleavage of the epoxide at first, which is considered as the rate-determining step of the polymerization. The formed zinc-alkoxide species then initiates the ROP of e-CL, affording most of the PCLs possessing one epoxide molecule embedded in the polymer chain and dihydroxyl terminals as revealed by the 1H NMR and MALDI-TOF MS spectroscopy. The PCL specimen with a corrected Mn of 110.4 kDa exhibits the tensile strength and elongation at break of as high as 40.2 MPa and 1060%, respectively. This work provides a facile and practical method for the synthesis of high-molecular-weight PCLs.

Aliphatic poly(monothiocarbonate)s synthesized by alternating copolymerization of carbonyl sulfide (COS) and epoxides are a new type of crystalline polymers. In this work, the isothermal crystallization behavior and spherulite morphology of poly(trimethylene monothiocarbonate) (PTMMTC) and poly(ethylene monothiocarbonate) (PEMTC) are studied. PTMMTC tends to form banded spherulites, especially at low crystallization temperatures, while PEMTC forms non-banded spherulites. The overall crystallization rate and spherulitic growth rate of PTMMTC are larger than those of PEMTC at the same degree of supercooling. PTMMTC with longer alkane segment in the main chain has a higher equilibrium melting temperature (Tm0) than PEMTC. Both polymers exhibit double melting peaks, but the formation mechanisms are different for PTMMTC and PEMTC. Small-angle X-ray scattering (SAXS) result reveals that more amorphous phases are located in interlamellae of PTMMTC, leading to a larger long period (L) and a thicker amorphous layers (la), which can account for the stronger tendency of PTMMTC to form banded spherulites. The melting enthalpies of PTMMTC and PETMC crystals with 100% crystallinity (ΔHm0) are obtained by extrapolating the melting enthalpies of the samples with different crystallinities. The free energy of the folding surface (σe) of PTMMTC is larger than that of PETMC, indicating that the PTMMTC chain is stiffer. The higher Tm0 and larger ΔHm0 and σe of PTMMTC can be attributed to its stronger interchain interaction.

Ring-opening polymerization (ROP) of the bioderived and nonstrained γ-butyrolactone (γ-BL) is an emerging approach to produce recyclable polymers. It remains a big challenge to synthesize high molecular weight linear poly(γ-butyrolactone)s (PγBLs) in a highly active and selective manner. In this report, we developed dual organocatalysts for the ROP of γ-BL, using symmetrical (thio)ureas with electron-donating groups to buffer the growing anions that were generared by the superbase phosphazene (P4). Linear PγBLs were selectively obtained with high apparent rate constant (ca. 39 times than single P4), and high number-average molecular weights of up to 64.3 kg/mol (ca. 3 times than single P4). The turnover frequencies of these P4/(thio)urea pair-catalyzed processes were as high as 125 h–1. High molecular weight PγBLs exhibited dramatically improved mechanical properties.

This review highlights recent advances in the synthesis of carbon dioxide (CO 2 )-based copolymers with both linear (di-, tri-, and multi-block, etc.) and non-linear (star-block and grafting) architectures. The corresponding catalytic systems are summarized. The microstructure and polymerization mechanism of various types of CO 2 -based copolymers, including block polycarbonates and block copolymers of polycarbonate with polyester, polyether, polyvinyl, and polydiene are discussed. The junction unit between two blocks, which indicates an abrupt change in the chain microstructure and property, is emphasized to define the microstructure of CO 2 -based block copolymers. Special attention was paid to one-pot terpolymerization for the synthesis of CO 2 -based block and grafting copolymers. Finally, the thermal, mechanical, and degradation properties and self-assembly of CO 2 -based block and grafting copolymers are reviewed. Prospective future research and applications of this new class of polymeric materials are discussed.

Polyester synthesis from the alternating copolymerization of epoxides with cyclic anhydrides via a metal-free route remains a key challenge. This work reports the development of a highly active organocatalytic route for the copolymerization of a spectrum of epoxides and cyclic anhydrides. Fully alternating polyesters were synthesized by a variety of organic Lewis acid–base pairs including organoboranes and quaternary onium salts. The effect of the acidity, type, and size of Lewis pairs on the catalytic activity and selectivity of the copolymerization is presented. The undesirable transesterification and etherification were effectively suppressed even in the case of complete conversion of the cyclic anhydride. This could be ascribed to the formation of a unique tetracoordinate bond-carboxylate (or alkoxide) anion. The Lewis pairs are highly active, with a turnover frequency of 102 and 303 h–1 for the copolymerization of propylene oxide with maleic anhydride and phthalic anhydride, respectively, at 80 °C. B...

Small quantities of regio-defects in a regio-/stereoregular polymer weaken its tacticity and properties. This work clarified the origin of the regio-defect in the process of synthesizing poly(monothiocarbonate) through the copolymerization of propylene oxide (PO) and carbonyl sulfide (COS) catalyzed by a (salen)CrCl complex accompanied by bis(triphenylphosphoranylidene)ammonium chloride ([PPN]Cl). Quantitative characterization results from the MALDI-TOF-MS and 1H (13C) NMR spectroscopy suggested that the chain transfer reaction resulted in the regio-defect in the final copolymer, i.e., tail-to-tail (T–T) diad and dithiocarbonate (DTC) unit. The chain transferring to water in the reaction system led to the production of a (salen)Cr–OH intermediate, which initiated the copolymerization via either attacking PO first to result in formation of a T–T diad or first activating COS to produce mercapto (−SH) end-capped dormant chains via decarboxylation, thus generating a DTC unit in the final product through anoth...

It is a challenging topic to disconnect a linear polymer selectively at the mechanophore site by an external force in a “cold” fashion. In this work, the effect of the power output of ultrasonication on the selective cleavage at the centered urfuryl-maleimide Diels–Alder (DA) mechanophore of poly(methyl acrylate)s (DA-PMA-a and DA-PMA-b) were quantitatively investigated by comparative study on experimental and simulated chain scission kinetics as well as high-resolution 1H NMR spectroscopy (600 MHz). At low power output of the ultrasonication (2.10 W), DA-PMA-a with Mn of ca. 2Mlim (Mlim, below which no further chain scission was observed) presented a DI (degradation index)−t (sonication time) plot with a turnover point at ca. 1.0 and no clear variation of the molecular weight after the turnover, which met well with the calculated center cleavage mode. At 5.52 W, DA-PMA-a and a poly(methyl acrylate) that contained two centered ester bonds (ester-PMA) presented similar DI–t plots with turnover points less ...

The fluorescent properties of a linear poly(hydroxyurethane) (P1) from carbon dioxide, siloxane (Si–O–Si)-containing bisepoxide and diamine are described. P1 showed strong photoluminescence with a quantum yield of up to 23.6%, high photostability, and broad absorption and emission spectra either in bulk or solution. The flexibility and hydrophobicity of the Si–O–Si linkage in P1 were utilized to drive the intense aggregation of hydroxyurethane chromophores which combined with the hydrogen bonding interactions lead to strong photoluminescence. P1 was used as a single phosphor film for fabricating a low voltage, cool white light-emitting diode device with competitive performances.

A semicrystalline poly(trimethylene monothiocarbonate) (PTMMTC) has been synthesized via the selective and alternating copolymerization of carbonyl sulfide and oxetane. This reaction was catalyzed by (salen)CrCl accompanied by organic bases over a wide range of temperatures from 40 to 130 °C. PTMMTC is shown to exhibit similar crystallization behavior to high-density polyethylene (HDPE), i.e., being spherulite and possessing melting temperatures (Tm) up to 127.5 °C and a degree of crystallinity (Xc) of up to 71%. Moreover, PTMMTC has a wide processing temperature window of ca. 100 °C.

Polythioesters represent a promising functional polymer owing to the ubiquity and uniqueness of thioester bonds, however, to develop new examples of (functionalized) polythioesters for broadening the range of their applications is a grand challenge. Here, we report a convenient synthesis of a polythioester incorporating both thioester and selenide groups in repeating units via the alternating copolymerization of γ-selenobutyrolactone with episulfides including propylene sulfide and cyclohexene sulfide. This process mediated by a relatively mild phosphazene base of P1 exhibits very high activity with turnover of frequency (TOF) values of up to 1200 h−1, in which the nucleophilic attack of a selenol-type anion to episulfides is convinced as the rate-determining step by kinetic investigations. The prepared poly(thioester-alt-selenide)s have rigorously alternating sequences under optimized reaction conditions, molecular weights of 2.5–12.8 kg/mol, glass-transition temperatures of as low as −45.2 °C. Of unique, this copolymer exhibits remarkably high refractive indices of up to 1.74, suggesting a potential application prospect in optical materials.

The most daunting challenge of solid polymer electrolytes (SPEs) is the development of materials with simultaneously high ionic conductivity and mechanical strength. Herein, SPEs of lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI)-doped poly(propylene monothiocarbonate)-b-poly(ethylene oxide) (PPMTC-b-PEO) block copolymers (BCPs) with both blocks associating with Li+ ions are prepared. It is found that the PPMTC-b-PEO/LiTFSI electrolytes with double conductive phases exhibit much higher ionic conductivity (2 × 10-4 S cm-1 at r.t.) than the BCP electrolytes with a single conductive phase. Concurrently, the storage moduli of PPMTCn -b-PEO44 /LiTFSI electrolytes are ≈1-4 orders of magnitude higher than that of the neat PEO/LiTFSI electrolytes. Therefore, simultaneous improvement of ionic conductivity and mechanical properties is achieved by construction of a microphase-separated and disordered structure with double conductive phases.

The alternating copolymerization of one-carbon (C1) building blocks including carbon dioxide (CO2) and its sulfur analogues of carbon disulfide (CS2) and carbonyl sulfide (COS) with epoxides afford new copolymers, namely polycarbonates and polythiocarbonates, with tailored chain structures and properties. This review mainly focuses on the recent advances in C1-involved copolymerization via heterogeneous catalysis of zinc-cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC] catalyst. The chemistry of zinc-hydroxyl bond of Zn–Co(III) DMCC is responsible to the copolymerization of these C1 monomers with epoxides through the formation of C–O (S) bond. The syntheses of CO2-based copolymers with various topologies are also reviewed in detail. The utilization of CO2, COS and CS2 as monomers for polymer synthesis have significant contributions to the sustainable use of renewable resources.

We describe the enhanced mechanophore activation within nanosized core–shell micelles, which also present temperature and ultraviolet (UV) light-responsive properties. The model micelle was fabricated by the self-assembly of an amphiphilic block copolymer of poly(tert-butyl acrylate-b-N-isopropylacrylamide) with one spiropyran (SP) moiety at the midpoint of chain [SP-(t-BA88-b-NIPAM62)2, P2]. Micellization of P2 in tetrahydrofuran (THF)/water mixed solvent enhanced the reactivity of the electrocyclic ring-opening reaction of SP to merocyanine (MC) isomer under sonication because micellization caused SP-centered PtBA block entangled and partially swelled in the micellar core and the increase of the dielectric constant of the medium around the SP, which could facilitate the conversion of SP to MC. This new enhanced mechanophore activation model demonstrated here is valuable as a probe to detect stress activation within nanosized particles and to design multiple-responsive materials.

The completely alternating copolymerization of carbonyl sulfide (COS) and styrene oxide was found to occur under mild reaction conditions (0–30 °C and 1.5 MPa) in the presence of (salen)CrCl/onium salt catalyst systems to afford high molecular weight poly(monothiocarbonates) with narrow molecular weight distributions. Ring-opening of styrene oxide was shown to be 88% selective at the methylene carbon. That is the reaction is driven by steric hindrance, where ring-opening occurs preferentially at the less congested carbon center. Similar results were found upon utilizing the tetramethyltetraazaannulene (tmtaa)CrCl/onium salt catalyst. On the other hand, upon employing a zinc–cobalt double metal cyanide (Zn–Co DMCC) catalyst, where the ligands around the active zinc site are not sterically encumbering, ring-opening of styrene oxide occurs predominantly at the methine carbon site; i.e., the reaction is electronically driven.

The catalytic coupling of oxetane, the symmetric isomer of propylene oxide, with carbon disulfide has been investigated utilizing (salen)CrCl in the presence of various onium salts. Oxygen and sulfur atom exchange was observed in both the polymeric and cyclic carbonate products. The coupling of oxetane and CS2 was selective for copolymer formation over a wide range of reaction conditions. Five different polymer linkages and two cyclic products were determined by 1H and 13C NMR spectroscopy, and these results were consistent with in situ infrared spectroscopic monitoring of the process. The major cyclic product produced in the coupling process was trimethylene trithiocarbonate, which was isolated and characterized by single crystal X-ray crystallography. Upon increasing the CS2/oxetane feed ratio, a decrease in the O/S scrambling occurred. The reaction temperature had the most significant effect on the O/S exchange process, increasing exchange with increasing temperature. The presence of the onium salt ini...

A novel and robust route for the synthesis of a new amphiphilic brush copolymer, poly(glycidyl methacrylate)-graft-polyethylene glycol (PGMA-g-PEG), with high grafting densities of 97%-98% through a "grafting onto" method via carbon dioxide chemistry is reported. PGMA-g-PEG can self-assemble and form stable spherical core-shell micelles in aqueous solution. Besides, the obtained PGMA-g-PEG polymer contains hydroxyurethane structures as the junction sites between the PGMA backbone and PEG side chain, which can be used for further modification.

In this study, we describe the substituent effect of epoxides on CO2/epoxide copolymerization catalyzed by a nanosized zinc–cobalt(III) double metal cyanide complex [Zn–Co(III) DMCC]. The Zn–Co(III) DMCC catalyzed the copolymerization of CO2 with 11 epoxides with alkyl or aryl groups at 50–60 °C within 15 h. The reaction afforded various CO2/epoxide copolymers with high epoxide conversion efficiencies up to 100%. The alternating degree (FCO2) of the resulting copolymer was solely decided by the steric hindrance of the substituents of the epoxides regardless of their electron-donating or withdrawing properties. Substituents with large steric hindrances (2, 2-dimethyl, tert-butyl, cyclohexyl, decyl, and benzyl) led to highly alternating degrees (up to 100%). The regioselective CO2/epoxide copolymerization was dominated by the electron induction effect of the substituent. The electron-withdrawing substituent such as phenyl and benzyl induced regioselective ring-opening at the methine site of the epoxide. For...

The degradation and reuse of epoxy thermosets have significant impact on the environments. We report that an epoxy–amine thermoset embedded with Diels–Alder (DA) bonds was transformed into soluble polymers via sonochemistry under mild temperature (ca. 20 °C) for the first time. Sonication could effectively induce the position-oriented cleavage of DA bonds (i.e., retro-DA) of the fully swelled epoxy thermoset in dimethyl sulfoxide (DMSO), leading to the soluble polymers. Of importance, such sonochemical process could be regulated on demand via switching on-and-off of the sonication. The obtained soluble polymers could be recured to form epoxy–amine thermosets via DA reaction. This sonochemical method might provide an unprecedented and efficient way to the controlled degradation and recycling of the epoxy thermosets containing the dynamic covalent bonds likes DA groups.

This paper describes the first example of alternating copolymerization of carbonyl sulfide (COS) with cyclohexene oxide (CHO) via heterogenous catalysis of a nano-lamellar zinc–cobalt(III) double metal cyanide complex (Zn–Co(III) DMCC), providing an efficient method for converting COS to poly(cyclohexene monothiocarbonate) (PCHMTC) with an alternating degree up to 93%. The number-average molecular weight (Mn) of PCHMTC was 6.5–25.0 kg/mol with polydispersities (PDIs) of 1.6–2.1. The productivity of the catalyst was up to 970 g polymer/g catalyst (5.0 h). The oxygen–sulfur exchange reaction (O/S ER) caused by Zn–Co(III) DMCC was largely suppressed when the reaction was performed at 100–110 °C in the presence of THF or CH2Cl2, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to 98%. The mechanisms of the copolymerization and O/S ER were proposed based on the ESI-MS, GC–MS and FT-IR spectra. The obtained PCHMTC is highly transparent and exhibits good solubility in various organic solvents, high Tg of 112 °C, initial decomposition temperature of 214 °C and high refractive index of 1.705.

This work describes the microphase separation behavior of poly(propylene monothiocarbonate)-b-poly(ethylene oxide) (PPMTC-b-PEO) block copolymers (BCPs), a type of new sulfur-containing block copolymer, induced by lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI). PPMTC-b-PEO BCPs with a fixed PEO block length but different PPMTC block lengths were synthesized and doped by LiTFSI. Temperature-variable small-angle X-ray scattering result indicates that microphase separation of the PPMTC-b-PEO BCPs can be induced by differential interactions with LiTFSI. However, the ability of LiTFSI to induce microphase separation in PPMTC-b-PEO BCPs does not monotonically increase with the doping ratio (r = [Li+]/([EO] + [PMTC])). It is observed that stronger microphase separation usually occurs at r = 1/12 and 1/6, but microphase separation is weaker at r = 1/24 and 1/3. In most cases, microphase-separated but disordered structures are obtained. Particularly, ordered lamellar structure is formed at suitable doping ratio and block composition. FTIR result confirms the differential complexation of LiTFSI with PEO and PPMTC. LiTFSI preferentially interacts with PEO at low rs, but also strongly interacts with PPMTC at high rs. This work provides a new method to prepare solid polymer electrolytes with double conductive nano-phases, which may be beneficial to both conducting and mechanical properties.

Epichlorohydrin (ECH), as a cheap raw chemical material, is an ideal monomer for copolymerization with CO 2 to produce biodegradable polycarbonates. This work describes the selective ECH–CO 2 copolymerization via heterogeneous catalysis of nanolamellar zinc–cobalt double metal cyanide complex (Zn–Co (III) DMCC), affording a poly(carbonate– co –ether) with carbonate content up to 70.7%. Remarkably, the cyclic carbonate contents in the product are 5.0%–11.3% at 25–60 °C, better than those from homogeneous catalysis. Moreover, the copolymer with 70.7% carbonate content presents high thermal decomposition temperature of 250 °C and relatively high glass-transition temperature ( T g ) of 31.2 °C.

We report the first example of a regioregular and fully alternating poly (propylene monothiocarbonate) (PPMTC) from the well-controlled copolymerization of two asymmetric monomers, carbonyl sulfide...

The adsorptions of a double thermo-sensitive pentablock terpolymer, PNIPAm 110 -PEO 100 -PPO 65 -PEO 100 -PNIPAm 110 (PNIPAm 110 -F127-PNIPAm 110 ), on hydrophobic gold surfaces at various temperatures were investigated by using quartz crystal microbalance (QCM), atomic force microscopy (AFM), and ellipsometry. The experimental results indicated that the adsorption kinetics, adsorbed amounts and morphologies of the adsorbed terpolymer layers were strongly dependent on the temperatures, which could be correlated with the chain conformation of PNIPAm 110 -F127-PNIPAm 110 in aqueous solution. At the low critical solution temperature (LCST) of PPO block (i.e. 31 °C), PNIPAm 110 -F127-PNIPAm 110 was adsorbed onto hydrophobic gold surface via a two-step adsorption process and adopted a brush-like conformation. While at the LCST of PNIPAm block (i.e. 34 °C), a complex multistep adsorption process was observed, which resulted in a large adsorption amount. By comparing with the adsorption behavior of F127 at the corresponding temperature, it was deduced that the large adsorption amount obtained at 34 °C was mainly attributed to the presence of PNIPAm blocks. The premicellar associative adsorption was thought to play an important role for the observation of this unexpected adsorption behavior at 34 °C, leading to the large adsorption amount and large aggregate structures as revealed by AFM.

Although zinccobalt (III) double metal cyanide complex (ZnCo (III) DMCC) catalyst is a highly active and selective catalyst for carbon dioxide (CO2)/cyclohexene oxide (CHO) copolymerization, the structure of the resultant copolymer is poorly understood and the catalytic mechanism is still unclear. Combining the results of kinetic study and electrospray ionization-mass spectrometry (ESI-MS) spectra for CO2/CHO copolymerization catalyzed by ZnCo (III) DMCC catalyst, we disclosed that (1) the short ether units were mainly generated at the early stage of the copolymerization, and were hence in the “head” of the copolymer and (2) all resultant PCHCs presented two end hydroxyl (OH) groups. One end OH group came from the initiation of zinchydroxide (ZnOH) bond and the other end OH group was produced by the chain transfer reaction of propagating chain to H2O (or free copolymer). Adding t-BuOH (CHO: t-BuOH = 2:1, v/v) to the reaction system led to the production of fully alternating PCHCs and new active site of ZnOt-Bu, which was proved by the observation of PCHCs with one end Ot-Bu (and OCOOt-Bu) group from ESI-MS and 13C NMR spectra. Moreover, Zn−OH bond in ZnCo (III) DMCC catalyst was also characterized by the combined results from FT-IR, TGA and elemental analysis. This work provided new evidences that CO2/CHO copolymerization was initiated by metalOH bond. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Traditional cobalt-zinc double metal cyanide complex [Zn–Co(III)DMCC] catalysts could catalyze the copolymerization of carbon dioxide (CO 2 ) with propylene oxide (PO) to afford poly (propylene carbonate) (PPC) with high productivity. But the molecular weight (MW) of PPC and the polycarbonate selectivity were not satisfied. In this work, by using a nanolamellar Zn–Co(III) DMCC catalyst, the CO 2 –PO copolymerization was successfully performed to yield PPC with high molecular weight ( M n : 36.5 kg/mol) and high molar fraction of CO 2 in the copolymer ( F CO 2 : 74.2%) at low polymerization temperatures (40∼80 °C). Improved selectivity ( F CO 2 : 72.6%) and productivity of the catalyst (6050 g polymer/g Zn) could be achieved at 60 °C within 10 h. The influences of water content on CO 2 –PO copolymerization were quantitatively investigated for the first time. It was proposed that trace water in the reaction system not only acted as an efficient chain transfer agent, which decreased MW of the resultant copolymer, but also strongly interacted with zinc site of the catalyst, which led to low productivity of PPC and more amounts of cyclic propylene carbonate (cPC). These conclusions were also supported by the apparent kinetics of CO 2 –PO copolymerization. ESI-MS results showed that all polymers have two end alkylhydroxyl groups. It was thus proposed that the alkylhydroxyl groups came from the initiation reaction of Zn–OH in the catalyst and the chain transfer reaction by H 2 O. The proposed mechanism of chain initiation, propagation and chain transfer reaction were proved by the experimental results.

Core crosslinked star (CCS) polymers, which have crosslinked poly (divinyl benzene-co-styrene) [P(DVB-St)] core and multiple arms of polystyrene- b -poly(ethylene oxide) diblock copolymer (PEO- b -PS) [denoted as PEO- b -PS/P(DVB-St) CCS], were synthesized via atom transfer radical polymerization(ATRP). PEO- b -PS/P(DVB-St) CCS polymer was spherical with average diameters of scores of nanometers from transmission electron microscopy (TEM) and dynamic light scattering (DLS), and blended with diglycidyl ether of bisphenol (DGEBA) and 4,4′-diamino diphenyl methane (DDM) in tetrahydrofuran (THF). With 5 or 10 wt% PEO- b -PS/P(DVB-St) CCS polymer, spherical core–shell nanodomains with average diameters of 29 or 32 nm were observed from atomic force microscopy (AFM), which were randomly distributed in the resultant thermosets. Considering the difference in miscibility of the epoxy with P(DVB-St) and PEO- b -PS after and before curing reaction, a reaction-induced microphase separation (RIMPS) mechanism was proposed to account for the formation of the core–shell nanodomains in the thermosets. During curing, the RIMPS of PS subchain occurred but was confined by P(DVB-St) core, resulting in formation of thermoplastic PS shell around the crosslinked core. Such core–shell nanodomain could be easily etched away by THF, whereas the control thermosets containing PEO/P(DVB-St) CCS polymer could not be etched by THF. The glass transition temperatures ( T g s) of the epoxy thermosets containing PEO- b -PS/P(DVB-St) CCS polymer were significantly improved compared with pure epoxy thermosets.

This paper describes a convenient one-pot terpolymerization of CO2, cyclohexene oxide (CHO) and maleic anhydride (MAH) to afford a poly (ester-carbonate) with a low content of ether units (2.9–4.3 mol%) using a highly active Zn–Co(III) double metal cyanide complex (DMCC) catalyst. Terpolymerization was carried out in tetrahydrofuran (THF) at 75–90 °C and 1.0–4.0 MPa and no cyclic carbonate was observed in NMR spectra. The number-average molecular weight (Mn) of the terpolymer was up to 14.1 kg/mol with a narrow molecular weight distribution of 1.4–1.7. The apparent efficiency of the catalyst was up to 12.7 kg polymer/g Zn, representing the highest catalytic activity for terpolymerization of CO2, epoxides and cyclic anhydrides to date. THF dramatically inhibited polyether formation in this terpolymerization owing to its nucleophilicity towards the Zn2+ center of Zn–Co (III) DMCC. This presents the first example of solvent-assisted selectivity for inhibiting ether units in CO2 polymerization catalyzed by a heterogeneous system. Kinetic analyses of MAH/CHO/CO2 terpolymerization (MAH/CHO 0.2) suggested that polyester production was slightly faster than polycarbonate production in the early stage. A mechanism for this terpolymerization catalyzed by Zn–Co (III) DMCC catalyst was proposed. Moreover, addition of small amounts of MAH (MAH/CHO molar ratio ≤0.2) during CO2/CHO copolymerization can improve the thermal properties of the resultant terpolymers.

The double thermosensitive and narrow dispersed PNIPAm110-PEO100-PPO65-PEO100-PNIPAm110 pentablock terpolymer was synthesized by the typical atomic transfer radical polymerization (ATRP) method with N-isopropylacrylamide (NIPAm) as the monomer and modified poly(ethylene oxide)100−poly(propylene oxide)65−poly(ethylene oxide)100 (PEO100-PPO65-PEO100) block copolymer as the macroinitiator. Microdifferential scanning calorimetry (micro-DSC) data showed that the pentablock terpolymer exhibited two low critical solution temperatures (LCSTs) at 31 and 34 °C in the aqueous solution, which can be attributed to the thermal phase transition of the PPO block and PNIPAm block, respectively. The chain conformation of the pentablock terpolymer in aqueous solution was then studied in detail by using a combination of static and dynamic laser light scattering (SLS-DLS). The SLS-DLS results indicated that the loose “associates” and single coil chains coexisted in the aqueous solution at the low temperature, where the PEO, P...

Highly active CaCl2-modified Zn-Co(III) DMCs were prepared. XRD results showed that the modified catalyst Ca-DMC containing 0.14 wt.-% CaCl2 was amorphous. A higher polymer yield (>61 kg polymer/g catalyst) and a shorter induction period for ROP of PO were observed for Ca-DMC than for unmodified DMC catalysts. An initiator had an inhibitory effect on the initiation and polymerization rate of PO ROP. As the molar ratio of the initiator functionality to the catalyst was increased, the reaction rate and polymer yield decreased, whereas the induction period increased. An increase in reaction temperature tended to reduce the polymer yield and broaden the MWD. The 13C NMR spectrum for an oligomer from a model polymerization without an initiator revealed that the main terminal unit of the polymer was CH2CH(CH3)OH because H2O in the system participated in reaction initiation. Cl− and t-BuOH may also initiate the reaction according to the small amounts of terminal CH2Cl and OC(CH3)3 units observed by 13C NMR spectroscopy. On the basis of common characteristics and some new evidence for DMC catalysis, a mechanism similar to a classical coordination insertion process is proposed.

Inherently flame retardant epoxy resin is a kind of halogen-free material for making high-performance electronic materials. This work describes an inherently flame retardant epoxy system composed of 4,4'-diglycidyl (3,3',5,5'-tetramethylbiphenyl) epoxy resin (TMBP), 1,2-dihydro-2-(4-aminophenyl)-4-(4-(4-aminophenoxy) phenyl) (2H) phthalazin-1-one (DAP), and hexa(phenoxy) cyclotriphophazene (HPCTP). The cure kinetics of TMBP/DAP in the presence or absence of HPCTP were investigated using isoconversional method by means of nonisothermal differential scanning calorimeter (DSC). Kinetic analysis results indicated that the effective activation energy (E α ) decreased with increasing the extent of conversion (α) for TMBP/DAP system because diffusion-controlled reaction dominated the curing reaction gradually in the later cure stage. TMBP/DAP/HPCTP(10 wt %) system had higher E α values than those of TMBP/DAP system in the early cure stage (α 0.60) due to kinetic-controlled reaction in the later cure stage. Such complex E α ∼ α dependence of TMBP/DAP/ HPCTP(10 wt %) system might be associated with the change of the physical state (mainly viscosity) of the curing system due to the introduction of HPCTP. These cured epoxy resins had very high glass transition temperatures (202-235°C), excellent thermal stability with high 5 wt % decomposition temperatures (>340°C) and high char yields (>25.6 wt %).

A bismaleimide monomer, 4,4′-bis(4-maleimidophenoxy)-3,3′,5,5′-tetramethyl biphenyl (BMITB), was synthesized in high yield (94%) via a facile four-step reaction from 2,2′,6,6′-tetramethyl-4,4′-biphenol. The chemical structure of BMITB was confirmed by FTIR, 1H NMR, 13C NMR and elemental analysis. The monomer used to modify the epoxy cresol-formaldehyde novolac resin (ECN)/diaminodiphenyl sulfone (DDS) system. Cured ECN/BMITB/DDS blends with higher BMITB content had two distinct glass transition temperatures that were above 250°C according to differential scanning calorimetry, indicating that an interpenetrated polymer network structure may be formed. The initial thermal decomposition temperature and integral procedure decomposition temperature of the cured ECN/BMITB/DDS blends were >390 and 1080°C, respectively, according to thermogravimetric analyses. No phase separation was observed in dynamic mechanical analysis of cured ECN/BMITB/DDS blends with small amounts of BMITB (5 and 10 wt%). POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers

This paper describes the curing behaviours, thermal properties and flame-resistance of a novel halogen-free epoxy hybrid thermoset, prepared by the curing reaction of hexakis (methoxymethyl) melamine (HMMM), a phosphorous- containing epoxy resin (EPN-D) with 9, 10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) group and phenol formaldehyde novolac (n-PF). The resultant thermosets showed high glass-transition temperatures (Tg, 123-147°C) as determined by thermal mechanical analysis (TMA), excellent thermal stability with high 5 wt% decomposition tempera- tures (Td,5% ≥ 308°C) and high char yields (Yc ≥ 39.4 wt%) from the thermogravimetric analysis (TGA). All the cured EPN- D/HMMM/n-PF hybrid resins achieved the UL 94 V-0 grade with high limited oxygen indices (LOI > 45.7). It is found that phosphorous and nitrogen elements in the cured EPN-D/HMMM/n-PF hybrid resins had a positive synergistic effect on the improvement of the flame retardancy.

Based on the self-condensation of hexakis(methoxymethyl)melamine (HMMM), the condensation between HMMM and phenol formaldehyde novolac resin (n-PF), and the addition reaction of diglycidyl ether of biphenyl A (DGEBA) and n-PF, a homogeneous, transparent hybrid thermoset was prepared via in situ polymerization of DGEBA, n-PF, and HMMM. No phase separations were observed even for the DGEBA/n-PF/HMMM hybrid thermoset containing 40 wt % HMMM. These hybrid thermosets had high glass-transition temperatures (98–127°C from differential scanning calorimetry and 111–138°C from dynamic mechanical analysis), excellent thermal stability with high 5 wt % decomposition temperatures (>322°C), high char yields (>24 wt %), and improved flame retardancy with high limited oxygen indices (>28.5). The excellent overall properties of these hybrid resins may lead to their applications in high-performance “green” electronic products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Air-stable hybrid catalysts of silicon dioxide/double metal cyanide complexes (Si-DMCCs) based on Zn 3 [Co(CN) 6 ] 2 (ZHCC) were prepared by an in situ solgel method. The Si-DMCCs showed low crystallinity and a nanolamellar structure with a thickness of ∼40-60 nm. In particular, a lamellar structure of regular hexagonal shape was observed for Si-DMCCs with low SiO 2 content. These catalysts had very high catalytic activity for alternating copolymerization of cyclohexene oxide (CHO) and carbon dioxide. A turnover number of 11,444, turnover frequency of 3815 h -1 , and apparent efficiency of 7.5 kg polymer/g ZHCC (∼24.0 kg polymer/g Zn) were achieved at 3.8 MPa and 100 °C. The poly(cyclohexenylene carbonate) (PCHC) polymers obtained were completely atactic with a molecular weight (M n ) of ∼10 kg/mol and polydispersity of 2.0-3.0. The PCHCs had a structure of nearly alternating CHO and CO 2 units, with a molar fraction of carbonate units of 0.44-0.47. Preliminary investigations of the mechanism suggest that nucleophilic attack by neighboring oxygen atoms is involved in copolymerization initiation with Zn-CO III DMCCs.

A soluble bisphenol containing azomethine moiety and aromatic ether linkage, 2,2'-bis {4-[4-(hydroxy) phenytiminomethylidene] phenoxyphenyl} propane (BHPP), was synthesized from the reaction of 4-hydroxybenzaldehyde with 2,2'-bis (4-aminophenoxy phenyl) propane (BAPP) and characterized by IR, H-1 NMR, C-13 NMR, and elemental analysis. To improve the overall properties of epoxy/diamine thermoset, ternary-curing systems combined BAPP/BHPP with diglycidyl ether of biphenyl A (DGEBA) were designed. It was found that the curing behavior and properties of the BAPP/DGEBA system changed dramatically due to the introduction of BHPP. The hybrid-curing agents BAPP/BHPP exhibited more reactivity toward oxirane group than did BAPP. All the epoxy thermosets had high thermal properties, e.g., glass transition temperatures (T(g)s) are between 145 and 170 degrees C, 5% weight loss temperatures over 329 degrees C, integral procedure decomposition temperature (IPDT) varied with 682-1085 degrees C and good flame retardancy for their high limited oxygen index (LOI) values beyond 28.4.