Initiating system Me_3SiCl/AlCl_3 for cationic polymerization of 1,3-pentadiene in toluene

Cationic polymerization of 1,3-pentadiene (PD) initiated by trimethylsilyl chloride/aluminium chloride (TMSCl/AlCl3) was carried out in toluene at 30℃.The polymer yield was increased by the addition of TMSC1.However,introduction of TMSC1 gave rise to a drop of the polymer molecular weight.Kinetic results demonstrated that the polymerization initiated by TMSCl/AlCl3 was 2.8 times faster than that induced by AlCl3 alone.Various ethers and ketones were used to mediate the initiating system TMSCl/AlCl3.The polymer yield and molecular weight of the polymer were decreased in the presence of ether.Ketones and ethers had different effects on the polymerization,and the polymer yield and molecular weight were lower than those initiated by AlCl3 alone or TMSCl/AlCl3 Structural evidence revealed that the polymerization was indeed initiated by AlCl3 and HCl rcsulting from hydrolysis of TMSC1 by adventitious water.     

RING-OPENING POLYMERIZATION OF l,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS(2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE)

The ring-opening polymerization of 1,4-dioxan-2-one (PDO) was carried out by lanthanum tris(2,6-di-tert-butyl-4-methylphenolate) (La(OAr)3) as novel single component initiator. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly(1,4-dioxan-2-one) (PPDO) were explored. PPDO with high viscosity average molecular weight of 1.95×105 can be prepared at 40℃when [PDO]/ [La(OAr)3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a "coordinationinsertion" mechanism with selective rupture of acyl-oxygen bond of PDO.     

Fabrication,structure and surface charges of albumin-chitosan hybrids

Protein-polymer hybrids consisting of protein and natural polymers or synthetic polymers exhibit superior properties to unmodified proteins,generating a high demand for these materials in the fields of medicine,biotechnology,and nanotechnology.Herein,protein-polysaccharide hybrids were fabricated via the formation of an amide bond between bovine serum albumin(BSA) and chitosan(CS) using N-ethyl-N-(3-dimethylaminopropyl) carbodiimide hydrochloride(EDC) as the couple reagent.FTIR spectrum reveals that the carboxyl group of BSA conjugated with the amino group of chitosan backbone.The molecular weight of BSA-CS hybrids was identified by matrix-associated laser desorption ionization time of flight mass spectra(MALDI-TOF MS) and sodium dodecyl sulfate polyacrylamide gel electrophoresis(SDS-PAGE).The maximum number of chitosan chains binding to each BSA molecule was estimated as 6,and the optimal number was estimated as 2.In addition,the secondary structure and surface property of BSA were dependent upon the number of polymer conjugating on protein.The secondary structure of BSA was not significantly changed,if a few chitosans were coupled with BSA.By further increasing the molar ratio of chitosan to BSA,the secondary structure of BSA was markedly damaged.The surface’s negative charges of modified BSA also decreased.The result of native polyacrylamide gel electrophoresis(native-PAGE) also demonstrated the changes in surface charges and molecular weight of BSA-CS hybrids.     

Synthesis and Characterization of Heterocyclic Functionalized Polymers by Click Reaction: Preparation of Magnetic Nanocomposites and Studies on Their Thermal,Mechanical, Photophysical and Metal Ions Removal Properties

This work reports synthesis and characterization of heterocyclic functionalized polymers, poly(triazole-etherimidazole)s(PTAEI), from a dialkyne-terminated compound, 3-(4,5-bis(4-(propargyloxy)phenyl)-1H-imidazol-2-yl)-9-ethyl-9H-carbazole, by using click reaction. PTAEIs were characterized and their properties such as solubility, thermal, mechanical, photophysical and metal ions adsorption were investigated. These polymers had weight average molar masses(Mw) in the range of 19100-26700 g/mol, exhibited excellent solubility in polar aprotic solvents and formed low-colored flexible thin films by solution casting method. They exhibited good thermal stability with glass transition temperatures(Tg) between 160 °C and 211 °C and 10% weight loss temperatures(T10%) in the range of 308-426 °C. Nanocomposites of PTAEIs with epoxide-terminated Fe3O4 showed that strong interfacial interaction between inorganic particles and the polymer matrix contributed to the enhanced thermal and mechanical properties. The photoluminescence intensity of the PTAEIs increased and the spectra red shifted with increasing Fe3O4 content. The PTAEIs and nanocomposites were tested for their extraction capability of metal ions from aqueous solutions either individually or in the mixture.     

Synthesis of polystyrene-styrene/butadiene diblock copolymers via reversible addition-fragmentation chain transfer miniemulsion polymerization

<正>Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ~1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.     

SINGLE LANTHANUM TRIS(N-PHENYLETHYL-3,5-DI-t-BUTYLSALICYLALDIMINATO)S INITIATOR FOR RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE IN BULK

A rare earth Schiff base complex:lanthanum tris(N-phenylethyl-3,5-di-t-butylsalicylaldiminato)s [La(OPEBS)_3] was successfully applied as single component initiator for the ring-opening polymerization of 1,4-dioxan-2-one (PDO) in bulk.The influence of reaction conditions,such as polymerization temperature,the molar ratio of the monomer to initiator (M/I) on the monomer conversion and molecular weight of the polymer has been investigated.Poly(1,4-dioxan-2-one) with a viscosity-average molecular weight (My...     

Controlled/living ring-opening polymerization of ε-caprolactone catalyzed by phosphoric acid

The bulk ring-opening polymerization(ROP) of ε-caprolactone(ε-CL) by various phosphoric acids using phenylmethanol as the initiator was conducted.1,1’-bi-2-Naphthol(BINOL)-based phosphoric acid was found to be an effective organocatalyst for ROP leading to polyesters at 90℃.The overall conversion to poly(ε-caprolactone) was more than 96% and poly(ε-caprolactone) with M w of 8400 and polydispersity index of 1.13 was obtained.1 H NMR spectra of oligomers demonstrated the quantitative incorporation of the protic initiator in the polymer chains and showed that transesterification reactions did not occur to a significant extent.The controlled polymerization was indicated by the linear relationships between the number-average molar mass and monomer conversion or monomer-to-initiator ratio.In addition,the present protocol provided an easy-to-handle,inexpensive and environmentally benign entry for the synthesis of biodegradable materials as well as polyesters for biomedical applications.     

RING-OPENING POLYMERIZATION OF 1,4-DIOXAN-2-ONE INITIATED BY LANTHANUM TRIS（ 2,6-DI-TERT-BUTYL-4-METHYLPHENOLATE）

The ring-opening polymerization of 1,4-dioxan-2-one （PDO） was carried out by lanthanum tris（2,6-di-tert-butyl-4- methylphenolate） （La（OAr）3） as novel single component initiaLor. The influences of polymerization reaction temperature and the molar ratio of monomer to initiator on the monomer conversion and molecular weight of poly（1,4-dioxan-2-one） （PPDO） were explored. PPDO with high viscosity average molecular weight of 1.95×10^5 can be prepared at 40℃ when [PDO]/ [La（OAr）3] molar ratio was 800. Mechanism investigation shows that the polymerization proceeds through a ＂coordination- insertion＂ mechanism with selective rupture of acyl-oxygen be,nd of PDO.     

Thioxanthene-9-thione Mediated MMA Polymerization

In the "cycloketyl radical mediated living polymerization"(CMP) process, a cycloketyl compound, [9,9′]bixanthenyl-9,9′ diol(BIXAN) was ultilized as initiator and mediator. The cycloketyl(CK) radical was used as the dormant radical to achieve the increase of molecular weight. Herein, a series of cycloketyl thioketones were synthesised by Lawesson's reagent by one step reaction with high yeild,and we found that, when a special cycloketyl thioketone compound, thioxanthene-9-thione(TXT), was added to a routine radical polymerization system, TXT could capture chain radical, and simultaneously formed an radical analogous to CK radical in structure,which could trigger the growth of polymer chains. This simple system was efficient to initiate the polymerization of methyl methacrylate(MMA) and in all cases the molecular weights increased with the increase of conversions. By the end-group analysis with 1 H-NMR and MALDI-TOF MS, it was confirmed that the P-STXT radical was used to control the polymerization. The re-initiating reactions were achieved when PMMA was used as the macro-initiator.     

Effects of amino groups and microstructure of organic mesoporous silica supported metallocene catalysts on ethylene polymerization

<正>Mesoporous silica(MS),3-aminopropyltriethoxysilane(APTES) modified mesoporous silica(AMS),bis(3- trimethoxysilylpropyl)amine modified mesoporous silica(BAMS) and APTES modified solid spherical silica(AS) were prepared and used to immobilize metallocene catalysts for ethylene polymerization.Gel permeation chromatography results showed that polyethylenes(PEs) catalyzed by AMS(or BAMS) supported metallocene catalysts at the molar ratios of Al/Zr =100,300 and 500 were of bimodal molecular weight distribution(BMWD);while PEs catalyzed by the above catalysts at the molar ratios of Al/Zr≥800 were of monomodal molecular weight distribution(MMWD).However,MS(or AS) supported metallocene catalysts could only produce PEs with MMWD in spite of the molar ratio of Al/Zr.It was because that AMS(or BAMS) supported catalysts possessed two active sites for ethylene polymerization at low molar ratios of Al/Zr due to the combination effects of mesopore geometrical constraint and amino groups of the supports,which was confirmed by X-ray photoelectron spectroscopy.This brings forward a novel and easy method for the synthesis of polyolefin with BMWD.     

Microemulsion Polymerization of Methyl Methacrylate

The microemulsion polymerization of methyl methacrylate was studied. The effects of feeding modes on the structure and the properties of the obtained polymer microlatex were investigated by measuring the conversion, the transmittance and the refractive index of the latex, and by measuring the particle size, the molecular weight and the glass transition temperature (T_g) of the polymers. The results show that compared to the batch feeding mode, the semi-continuous feeding mode is more favorable to form a PMMA microlatex with a higher transmittance, a smaller particle size, a higher molecular weight and a higher T_g. And the obtained PMMA microlatex has a 30％—40％ (mass fraction) polymer content, a 0. 03 emulsifier/water weight ratio, a 0. 05 emulsifier/monomer weight ratio and a 17 nm average particle diameter, which is very important for the industrialization of the microemulsion polymerization technique.     

A New Process for Synthesis of Dimethyl Carbonate from Ethylene Carbonate and Methanol without any Catalyst under Supercritical Conditions

Dimethyl carbonate was synthesized by transesterification reaction between ethylene carbonate and methanol under supercritical conditions without any catalyst. Experimental results showed that the residence time and the molar ratio of methanol to ethylene carbonate all can affect the conversion of ethylene carbonate. When the molar ratio of methanol to ethylene carbonate was 8:1, 81.2% conversion can be achieved at 9.0 MPa and 250℃ after 8 h.     

Synthesis and Antibacterial Activity of Selenium-functionalized Poly(ε-caprolactone)

A selenium-functionalizedε-caprolactone was synthesized by introducing a phenyl selenide group at the 7-position.A polymer was obtained through the ring-opening polymerization of this monomer in a base/thiourea binary organocatalytic system.A living polymerization process was achieved under mild conditions.The resulting polymers had a controlled molecular weight with a narrow molecular weight distributions and high end-group fidelity.Random copolymers could be obtained by copolymerizing this monomer withε-caprolactone.The thermal degradation temperature of the obtained copolymers decreased with the increasing molar ratio of selenide functionalized monomer in copolymers,while the glass transition temperature increased.In addition,the phenyl selenide side group could be further modified to a polyselenonium salt,which resulted in a polymer with good antibacterial properties.The survival rate of E.coli and S.aureus was only 9%with a polymer concentration of 62.5μg/mL.     

RING-OPENING POLYMERIZATION OF TRIMETHYLENE CARBONATE BY CALIX[8]ARENE-NEODYMIUM*

Ring-opening polymerization of trimethylene carbonate (TMC) with a rare earth calixarene compound as catalysthas been studied for the first time. The effect of TMC/Nd (molar ratio) and polymerization conditions were investigated indetail. It was found that calix[8]arene-neodymium is a highly effective catalyst for the bulk polymerization of TMC and giveshigh molecular weight (M_v = 60,000) polymer. The optimum conditions of TMC polymerization were found to be asfollows:TMC/Nd (molar ratio) = 2,000, 80℃, 16 h. The polymers were characterized by NMR, GPC and DSC. Studying themechanism by NMR showed that the polymerization of TMC catalyzed by calix[8]arene-neodymium proceeds via a cationicmechanism.     

Preparation for Supramolecular Complexes of Chiral Diols BDPDD,DMBDPD and BINOL with Some Prochiral Compounds

Interaction between chiral diols BDPDD,DMBDPD and BINOL with prochiral compounds was examined and some new supramolecular complexes were prepared.It was found that these chiral hosts could include prochiral guests,α，β-unsarurated compounds or pinperazinedione derivatives to give inclusion crystals in different molar ratio.Formations of these supramolecular complexes were characterized by the data of IR and ^H NMR spectra.     

Novel smart supramolecular metallo-hydrogel that could selectively recognize and effectively remove Pb2+ in aqueous solution

A series of novel and simple ligands based on a biscarboxyl-functionalized benzimidazole derivative were synthesized.The experiments showed that the ligand L2 as a low molecular weight(LMW) hydrogelator could form stable metallo-hydrogels in the presence of up to 0.3 equiv.of lead ions.The metallo-hydrogels were characterized using powder X-ray diffraction,scanning electron microscopy(SEM),and Fourier transform infrared(FT-IR) spectroscopic techniques.When the molar ratio of L2:Pb2+ was in the range of 1:0.3 to 1:0.5 a translucent gel was produced.When the L2:Pb2+ molar ratio was higher than 1:0.5 the resulting gel tended to be opaque.The morphologies of these metallo-hydrogels were L2/Pb ratio dependent,ranging from worm-like to rod-shaped and nanofibrous.The FT-IR and X-ray diffraction(XRD) studies revealed that L2-Pb complexation was the main driving force for the formation of the metallo-hydrogels.In addition,these metallo-hydrogels exhibited outstanding thermostability and thermoreversibility,and displayed a reversible sol-gel transition induced by changes in pH and EDTA concentration.Importantly,ligand L2 showed an excellent capacity for the removal of Pb 2+ in aqueous solution through the formation of metallo-hydrogels.At a L2:Pb molar ratio of 1:0.5 and below,the concentration of residual Pb2+ was as low as 7.6×10-5 mol/L in aqueous solution,and the removal ratio was as high as 95.4%.These results demonstrate that multi-channel responsive smart metallo-hydrogels have the potential to be widely applied in materials science,and might provide the basis for lead pollution capture and removal.     

Polymerization of MMA catalyzed by different novel mixed ligand lanthanocene{(Cp)(Cl) LnSchiff-base (THF)},(COT) -Ln(methoxyethylindenyl)(THF) /Al (i -Bu)_3 systems

This article deals that the rare earth metal complexes along with Al(i'-Bu),can catalyze the polymerization of methyl-methacrylate (MMA) into high molecular weight poly(MMA) along with narrow molecular weight distributions (MWD).A typical example was mentioned in the case of {Cp(Cl) Sm-Schiff-base(THF)} which expresses maximum (conv.% = 55.46 and Mn=354×103) efficiency along with narrow MWD (Mw/Mn<2) at 60℃.The resulting polymer was partially syndiotactic (>60%).The effect of the catalyst,temperature,catalyst/MMA molar ratio,catalyst/Al( i-Bu)3 molar ratio on the polymerization of MMA at 60℃ were also investigated.     

Study on preparation and properties of polyether polytriazole elastomers

To explore the application of click chemistry in the field of elastomer materials, propargyl-terminated ethylene oxide-tetrahydrofuran copolymer(PTP(E-co-T)) was prepared from hydroxyl-terminated ethylene oxide-tetrahydrofuran copolymer(P(E-co-T)) by end-etherisation modification. FTIR and 13C-NMR results indicate that P(E-co-T)-terminated hydroxyl was etherified thoroughly, yielding the target product PTP(E-co-T), and the content of terminated alkynyl of PTP(E-co-T) was evaluated to be 0.428 mmol·g-1. Using a polyazide compound as a cross-linker, polytriazole elastomers with various functional molar ratio(R) values were prepared from PTP(E-co-T) by virtue of the Cu AAC reaction. Mechanical property tests indicate that with the increase in R, the modulus E and stress σb of the polytriazole elastomers first increase and subsequently decrease, whereas the strain first decreases and later increases. The mechanical properties of the polytriazole elastomers show a parabolic dependence on the R value. Near the stoichiometric ratio, E and σb show maxima and the strain εb shows a minimum. Swelling tests demonstrate that the apparent molecular weight of polytriazole elastomer strands also first decreases and subsequently increases. At the stoichiometric ratio, the network structure possesses strands with a minimum apparent molecular weight and a maximum apparent density. Dynamic mechanical analysis reveals that the polytriazole elastomers presented damping peaks at approximately-64 °C, corresponding to the glass transition of copolyether strands, and the elastomer exhibited the lowest dissipation factor tanδ at the stoichiometric ratio. Thermal analysis suggests that the weight-loss process of the polytriazole elastomer is characteristic of one-step decomposition, and the elastomer begins to decompose from polyether strands, not triazole groups.     

Synthesis of C_2 oxygenated compounds from syngas in supercritical cyclohexane

Catalytic synthesis of C2 oxygenated compounds from syngas in supercritical cyclohexane was reported in this paper. The effect of the molar ratio of media to feed on the conversion and selectivity was mainly discussed. The results showed that the selectivity of C2 oxygenated compounds in supercritical cyclohexane was greatly improved, and the by-products of acetic acid, ace tic ester and alkanes were efficiently suppressed. Although the CO conversion was slightly declined, the space-time yield of C2 oxygenated compounds basically kept the constant at high media/feed ratio.     

SYNTHESIS AND FREE RADICAL POLYMERIZATION OF 2-OXO-3-METHYLEN E-5-PHENYL-1,4-DIOXAN

The novel cyclic monomer, 2-oxo-3-methylene-5-phenyl-1,4-dioxan, was synthesized by a set of reactions. Several intermediates were prepared and characterized in order to determine the monomer structure. The presence of chiral centers in the intermediates and resulting monomer makes it complicated to separate , purify and characterize them. It is a very reactive monomer which will polymerize even at room temperature if expose to moisture and air. This monomer can undergo essentially quantitative flee radical ring opening polymerization. The driving force for ring opening is the formation of new carbonyl group and benzylic radical. The monomer and polymer structure were established by IR, ~1H NMR, ~(13)C NMR and elemental analysis or high resolution mass spectrum. The molecular weight of the resulting polymer was estimated by viscosity determination.