PERFORMANCE AND INITIATION MECHANISM OF ISOPROPYLTHIOXANTHONE IN SURFACE PHOTOGRAFTING

In a polymerization model with low density polyethylene (LDPE) as the substrate and acrylic acid (AA) as the monomer, the performance of isopropylthioxanthone (ITX) in initiating surface photografting polymerization was evaluated. The results show that the reactivity of photopolymerization and photografting of ITX locate between benzophenone (BP) and benzildimethylketal (BDK) for polymerization, BDK > ITX > BP; for surface grafting polymerization, BP > ITX > BDK. These results can be explained by a reaction mechanism of the inter-molecular or intra-molecular hydrogen abstraction reaction of ITX.

Conventional Radical and RAFT Alternating Copolymerizations of Hydroxyalkyl Vinyl Ethers and Dialkyl Maleates

The alternating copolymerization of hydroxyalkyl vinyl ethers and dialkyl maleates is investigated by conventional radical polymerization and reversible addition-fragmentation chain transfer polymerization(RAFT).The influence of comonomer structure,comonomer feeding ratios,and monomer concentrations on the copolymerization and the copolymer structure have been investigated systematically.With 2-hydroxyethyl vinyl ether(HEVE)and dimethyl maleates(DMM)as comonomers,a well-defined alternating copolymer is prepared with M_(n)=3400 and M_(w)/M_(n)=1.93 up to 71.6% monomer.The alternating sequential chain structure of the copolymers has been proved by both NMR and matrixassisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS).The experimental reactivity ratios and theoretical calculated highest occupied molecular orbital and the lowest unoccupied molecular orbital of vinyl ethers and alkyl maleates support that these monomer pairs have tendency to form alternating copolymers.With 2-cyanopropan-2-yl N-methyl-N-(pyridin-4-yl)carbamodithioate as the RAFT agent,the molecular weight of HEVE and DMM copolymer increases with the monomer conversion,demonstrating a controlled radical polymerization feature with well-controlled molecular weight and relatively narrower molecular weight distribution.With alternating copolymer of HEVE and DMM as macro-CTA(M_(n)=5200 and M_(w)/M_(n)=1.46),both the chain extension with HEVE and DMM(M_(n)=10400 and M_(w)/M_(n)=1.72)and block copolymerization with vinyl acetate have been successfully achieved(M_(n)=8500 and M_(w)/M_(n)=1.52).

Synthetic Features and Mechanism for the Preparation of Vinyl Chloride-co-Butyl Acrylate-co-Vinyl Acetate Terpolymer via Precipitation Polymerization

Without any type of su rfactant or dispersing agent,precipitation polymerization has great superiorities in both polymer synthesis and applications.In the present work,the polymerization of vinyl chloride(VC),n-butyl acrylate(BA),and vinyl acetate(VAc)are conducted in the precipitation polymerization system and series of their random terpolymers poly(vinyl chloride-co-n-butyl acrylate-co-vinyl acetate)(PCBV)are synthesized successfully.The effects of various polymerization conditions,including solvent polarity,temperature,initiator concentration,and monomer feed ratios on the polymerization kinetics,number-average molecular weight(M_(n)),and terpolymer composition are investigated systematically.The solvent and the monomer feed ratio are crucial factors not only for the polymer morphology,but also for the reaction kinetic.In the non-polar solvent such as n-hexane,the PCBV displays particle morphology when the composition of BA ratio lower than 10 wt%.Otherwise,the PCBV forms a uniform polymer phase and precipitates out from the mixture.In the polar solvent,e.g.,dimethyl carbonate(DMC)and ethanol,the PCBV polymer maintains a slurry state either in low or in high monomer feed ratio.Impressively,VC based ternary copolymer that obtained in n-hexane has much lower M_(n)(<20 kDa)and much higher BA units mass fraction(>40 wt%)compared with emulsion and suspension polymerization.Additionally,the terpolymer can be easily sepa rated by simple centrifugation.

The Anhydride-Amic Acid-Imide Forms of Maleinized Soybean Oil

Vegetable oil is one of the most promising renewable feedstocks as an alternative to fossil resources,but there are few studies aiming to transform it into hydrophilic materials.We proposed a facile method to prepare water-soluble derivatives from soybean oil,which could become water resistant again after simple heat treatment.The model vegetable oil,soybean oil(SO),was first reacted with maleic anhydride(MA)by the Alder ene reaction to obtain maleinized soybean oil(SOMA),and SOMA was further reacted with gaseous ammonia to obtain the maleamic acid form(SOMA-Amic acid),which was very soluble in water(solubility>100 mg/mL).The obtained water-soluble product was converted to the water-resistant maleimide form(SOMA-Imide)by a simple heat treatment.The potential application of these vegetable oil derived materials was demonstrated in paper sizing as an example.SOMA-Amic acid was demonstrated to be a novel green material,which can be used in an aqueous process and then heat-treated to become water-resistant in the final product.

Preparation of Ultralow Molecular Weight Poly(vinyl chloride) with Submicrometer Particles via Precipitation Polymerization

Poly(vinyl chloride), with ultralow molecular weight, produced by free radical polymerization either at high temperature or in the presence of chain transfer agents, is widely used as special resins and polymer process additives. This paper reports a new process, called self-stabilized precipitation polymerization, in which the polymerization of vinyl chloride monomer (VCM) is conducted in hydrocarbon diluents without addition of any suspending agent or emulsifier. The merits of this novel strategy include:(1) PVC resins with ultra-low number-average molecular weight (Mn) from 4000 to 15000, which is much lower than Mn of those prepared by conventional suspension and emulsion polymerizations,(2) sub-micrometer PVC particles with near spherical morphology, and (3) the very simple post-polymerization separation process. Under mild stirring, polymerization proceeds stably and smoothly. The influences of main process factors, such as solvents, initiator and monomer concentrations, polymerization time, and temperature on both particle morphology and Mn of the polymer products are investigated systematically. The molar ratio of-CH2-CHCl-/-CH=CH-CH2CHCl, a good indicator of structural defects, is about 1000/0.1 which means the low molecular weights do not result from chain transfer to the monomers. Then the mechanism of this polymerization is proposed. In summary, this novel polymerization technology provides a straightforward method for preparing PVC particulate products with low Mn.

Synthesis and Characterization of Crystallizable Aliphatic Thermoplastic Poly(ester urethane) Elastomers through a Non-isocyanate Route

A simple non-isocyanate route is developed for synthesizing crystallizable aliphatic thermoplastic poly（ester urethane） elastomers （TPEURs） with good thermal and mechanical properties. Three prepolymers of 1,6-bis（hydroxyethyloxycarbonylamino） hexane （BHCH）, i.e. PrePBHCHs, were prepared through the self-transurethane polycondensation of BHCH. A poly（butylene adipate） prepolymer （PrePBA） with terminal HO-- groups was prepared and used as a polyester glycol. A series of TPEURs were prepared by the co-polycondensation of the PrePBHCHs with PrePBA at 170 ℃under a reduced pressure of 399 Pa. The TPEURs were characterized by gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray diffraction, atomic force microscopy, and tensile test. The TPEURs exhibited Mn up to 23300 g/mol, Mw up to 51100 g/mol, Tg ranging from -33.8 ℃ to -3.1 ℃, Tm from 94.3 ℃ to 111.9 ℃, initial decomposition temperature over 274.7℃, tensile strength up to18.8 MPa with a strain at break of 450.0%, and resilience up to 77.5%. TPU elastomers with good crystallization and mechanical properties were obtained through a non-isocyanate route.

Coral-shaped and Core-Shell Structure Copolyethylene Nanocomposites Particles Prepared by in situ Coordination Polymerization

The example of the preparation ofnano- and micro-scaled, coral-shaped and core-shell topological morphology of copolyethylene particles promoted by the novel heterogeneous non-metallocene catalyst （m-CH3PhO）TiC13/carbon nanotubes （CNTs） was reported. Mass fraction of titanium component of the catalyst was 4.0 wt% determined by ICP analysis. The catalyst system can effectively catalyze polymerization of ethylene and eopolymerization of ethylene with 1-hexene. Morphological examination of the obtained polymer particles was carried out by scanning electron microscope （SEM） and high resolution transmission electron microscope （HR-TEM） technique. The results revealed that the morphology of the nascent copolyethylene particles looked like coral shape with size in micro-scaled and featured the core-shell structure consisting of CNTs as the core and copolyethylene as the shell.

“SERGEANTS AND SOLDIERS RULE” IN HELICAL SUBSTITUTED- ACETYLENE COPOLYMER EMULSIONS

The ＂sergeants and soldiers rule＂ occurring in helical copolymer emulsions derived from an achiral monomer （M1） and a chiral monomer （M2） was observed. TEM, GPC, and 1H-NMR techniques in combination demonstrate the formation of nanoparticles constituted by the copolymers. CD and UV-Vis spectra show the （co）polymer chains in the nanoparticles adopt helical structures of a predominant helicity, and the copolymers follow the ＂sergeants and soldiers rule＂ in forming helical structure.

Aliphatic Thermoplastic Poly(ether urethane)s Having Long PEG Sequences Synthesized through a Non-isocyanate Route

A non-isocyanate route for synthesizing thermoplastic polyurethanes with excellent thermal and mechanical properties was described. Melt transurethane polycondensation of 1,6-bis（hydroxyethyloxy carbonyl amino）hexane with four poly（ethylene glycol）s （PEGs）, i.e. PEG400, PEG600, PEG1000, or PEG1500, was conducted at different molar ratios. A series of thermoplastic poly（ether urethane）s （TPEUs） with long PEG sequences were prepared. The TPEUs were characterized via gel permeation chromatography, FTIR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray scattering, and tensile tests. The TPEUs exhibit Tg between 12.4 ℃ and -40.4 ℃, Tm of up to 149.8 ℃, and initial decomposition temperature over 239.4 ℃. The tensile strength of the TPEUs reaches 38.39 MPa with a strain at break of 852.92%.

SYNTHESIS AND CHARACTERIZATION OF BIODEGRADABLE POLYESTERAMIDES CONSTRUCTED MAINLY BY ALTERNATING DIESTERDIAMIDE UNITS FROM N,N'-BIS(2-HYDROXYETHYL)-ADIPAMIDE AND DIACIDS

Two kinds of aliphatic alternating polyesteramide prepolymers were prepared through melt polycondensation from N,N＇-bis（2-hydroxyethyl）-adipamide and adipic acid or sebacic acid. Chain extension of them was conducted with 2,2＇-（1,4- phenylene）-bis（2-oxazoline） and adipoyl biscaprolactamate as combined chain extenders. The chain extended polyesteramides （ExtPEAs） were characterized by IR, 1H-NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X-ray scattering, tensile test and enzymatic degradation. The results showed that the ExtPEA（4,m）s were mainly constituted with the diester adipamide alternating units. ExtPEA（4,4） and ExtPEA（4,8） had Tm of 83.8℃ and 85.8℃ and initial decomposition temperature above 310.0℃. They crystallized similarly as Nylon-66 did and were flexible thermoplastic materials with tensile strength up to 25.64 MPa and strain at break up to 737%.

Controlled Radical Polymerization of Styrene Mediated by Xanthene-9-thione and Its Derivatives

In our present work, a novel controlled radical polymerization system is developed based on xanthene-9-thione （XT）. It was found that the radical polymerization of styrene （St） became controlled in the presence of a small amount of XT. At the early stage of the polymerization, the polymerization rate was relatively low and the as-formed polystyrene （PS） had low number-average molecular weight （Mn） and narrow polydispersity （D）. After XT was consumed, the polymerization rate increased dramatically and the Mn of PS increased gradually with polymerization proceeding. When the polymerization of St was carried out with a proper molar ratio of initiator to XT and at an appropriate temperature, shortened slow polymerization stage and good control over Mn could be achieved. To further improve the regulating ability of XT, a series of substituent groups （-CF3, --CH（CH3）2, --N（CH3）2） were introduced onto the xanthene ring of XT, and the effects of these derivatives on the polymerization of St were investigated in detail. UV-Vis spectroscopy was carried out to monitor the concentration of XT during the polymerization and the chemical structure of the as-formed PS was fully characterized by IH- NMR and ESI-MS analysis. A possible mechanism involving the formation and evolution of the cross-termination products was proposed to interpret the observed polymerization behavior.

A facile method to prepare polypropylene/poly(butyl acrylate)alloy via water–solid phase suspension grafting polymerization

Polypropylene/poly（butyl acrylate） alloy is produced by water-solid phase suspension grafting polymerization with a submicrometer microdomain where graft polymerization occurs within micropores of polypropylene particles prepared by reactor granule technology （RGT）. The results show that the grafting percentage （GP） of butyl acrylate （BA） increases with the increase of the monomer concentration, which could reach 32.6% while the grafting efficiency （GE） is up to 98%. The addition of the crosslinking agent, triethylene glycol diacrylate （TEGDA）, could improve GP up to 36.3%. Transmission electron microscopic （TEM） micrographs demonstrate that PBA microdomains distributed in PP matrix increase in size less than 500 rim. Moreover, TEM images show that the grafting phase exhibits a singlephase behavior with the addition of TEGDA, which implies that the ratio of graft copolymer increased.

Photo-grafting Poly(acrylic acid) onto Poly(lactic acid) Chains in Solution

Poly(lactic acid)(PLA)is one of the most important bio-plastics,and chemical modification of the already-polymerized poly(lactic acid)chains may enable optimization of its material properties and expand its application areas.In this study,we demonstrated that poly(lactic acid)can be readily dissolved in acrylic acid at room temperature,and acrylic acid can be graft-polymerized onto poly(lactic acid)chains in solution with the help of photoinitiator benzophenone under 254 nm ultraviolet(UV)irradiation.Similar photo-grafting polymerization of acrylic acid(PAA)has only been studied before in the surface modification of polymer films.The graft ratio could be controlled by various reaction parameters,including irradiation time,benzophenone content,and monomer/polymer ratios.This photo-grafting reaction resulted in high graft ratio(graft ratio PAA/PLA up to 180%)without formation of homopolymers of acrylic acid.When the PAA/PLA graft ratio was higher than 100%,the resulting PLA-g-PAA polymer was found dispersible in water.The pros and cons of the photo-grafting reaction were also discussed.

Reactive poly(divinyl benzene-co-maleic anhydride) nanoparticles:Preparation and characterization

Polymeric nanoparticles（NPs）have drawn great interest in the past few years due to their potential applications in the felds of biomedical and optical technologies.However,it is still a challenge to prepare functional polymeric NPs,especially for particle diameters smaller than 50 nm.In this work,we demonstrate a one-pot method to fabricate reactive poly（divinyl benzene-co-maleic anhydride）NPs（PDVBMAH NPs）through a self-stable precipitation polymerization process.The size and morphology of these PDVBMAH NPs were characterized in detail by scanning electronic microscopy,and their chemical structure was determined by IR.The results showed that these NPs were highly cross-linked and their diameter was about 30 nm with narrow distribution.Additionally,the DVB and MAH endow the NPs with reactive surface anhydride and pendant vinyl groups,and these particles could be further functionalized through reaction of these groups.A plausible pathway was proposed for the formation of PDVBMAH NPs.

Facile Construction of Synergistic β-Glucosidase and Cellulase Sequential Co-immobilization System for Enhanced Biomass Conversion

Converting renewable cellulose into glucose via cellulase catalysis for further production of biofuel has been recognized as one of the most promising ways for solving energy crisis.However,the hydrolysis performance of immobilized cellulase was not satisfactory for practical application due to the reduced catalytic efficiency and lack of β-glucosidase(BG)component in cellulase.Here,a facile method was developed to sequentially co-immobilize BG and cellulase by polymeric microparticles with hierarchical structure.In this strategy,BG was firstly entrapped into the cross-linked poly(ethylene glycol)(PEG)microparticles via inverse emulsion polymerization initiated by isopropyl thioxanthone(ITX)under the irradiation of visible light,leaving the formed ITX semi-pinacol(ITXSP)dormant groups on surface of BG-loaded microparticles,which could be further activated by visible light irradiation and initiated a graft polymerization to introduce poly(acrylic acid)(PAA)brush on the PEG core.After that,cellulase was covalently bonded on the PAA chains via carbodiimide reaction.The synergic effect of BG and cellulase was verified in the dual enzyme immobilization system,which led to a better stability at a wide range of temperature and pH than free enzymes.The dual enzymes system exhibited excellent reusability,which could retain 75%and 57%of the initial activity after 10 cycles of hydrolysis of carboxyl methyl cellulose and 5 cycles of hydrolysis of filter paper,respectively,indicative of the potential in biofuel areas in a cost-effective manner.

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 cyeloketyl 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 1H-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.