EFFECT OF SOLVENT ON THE COPOLYMERIZATION OF 2,2,6,6-TETRAMETHYL 4-PIPERIDINYL METHACRYLATE WITH STYRENE

The radical copolymerizations of 2,2,6, 6-tetramethyl 4-piperidinyl methacrylate (TMPM) with styrene in various solvents have been studied. The monomer reactivity ratios r_1 and r_2 were determined. It is observed that in all of these reaction systems, there are appreciable solvent effects on both r_1 and r_2, which can be correlated to the difference in chemical shifts of olefinic protons of TMPM. And the variance of the copolymer microstructure in various media was discussed.     

SYNTHESIS AND THERMAL PROPERTIES OF A NEW CHOLIC ACIDCONTAINING COPOLYMER

A new copolymer was synthesized by free radical polymerization in solution from methyl 3α-methylacryloyl-7α, 12α-dihydroxy-5β-cholan-24-oate (MACAME) and maleic anhydride (MAN). The copolymer was characterized by FT-IR and functional group analysis. The reactivity ratios of the two monomers were estimated [r_1 = 11.6 (MACAME), r_2 = 0.01(MAN)] by conducting a series of copolymerizations with a variety of monomer feed compositions and analyzing thecopolymer composition. Thermogravimetric and differential scanning calorimetric analyses of the samples indicate that thecopolymer possesses good thermal stability. The temperature at which the copolymer samples experienced a 10% weight loss(T_(WL)) is over 287℃, and the T_g ranged from 174 to 185℃ for the copolymers.     

EFFECT OF TEMPERATURE ON COPOLYMERIZATION PARAMETERS OF HYDROXYETHYL ACRYLATE AND METHYL METHACRYLATE

The copolymerization of 2-hydroxyethyl acrylate (HEA, M_1) and methylmethacrylate (MMA, M_2) in cyclohexanone was studied. The multiple experiments ofsolution copolymerization with low conversion were carried out at two sensitive compositionfeed points at 60, 80, 100, 120 and 140℃, respectively. The composition of the copolymerswas analyzed by ~1H-NMR. The reactivity ratios which were estimated by the Error-in-Variable Method (EVM) of Mayo-Lewis equation were found to be r_1 = 0.328, r_2 = 1.781for 60℃; 0.375, 1.709 for 80℃; 0.406, 1.654 for 100℃; 0.439, 1.540 for 120℃ and 0.455,1.400 for 140℃, and the 95% joint confidence intervals of the reactivity ratios were alsodetermined. According to r_1 and r_2, Arrhenius relations and the activity energy differencebetween the homo- and cross-propagation were calculated.     

COPOLYMERIZATION AND DETERMINATION OF MONOMER REACTIVITY RATIOS OF DL-LACTIDE WITH 3-BENZYLOXYMETHYL-1,4-DIOXANE-2,5-DIONE

The copolymerization of DL-LA and 3-BMG was carried out in bulk with Stannous 2-ethylhexanoate as thecatalyst. A series of copolymers with pendant protected groups were obtained and characterized by ~1H-NMR and GPCanalysis. The monomer reactivity ratios were evaluated by the Fineman-Ross method and the Kelen-Tudos method and foundto be r_(BMG) = 1.96 and r_(LA) = 0.37, respectively.     

REACTIVITY RATIOS FOR COPOLYMERIZATION WITH THE PARTICIPATION OF A CHARGE-TRANSFER COMPLEX

The complexation between styrene (St) and N-phenylmaleimide (PMI) was investigated by ~1H-NMR spectroscopy,and the existence of a complex was proved. The equilibrium constant of St/PMI in chloroform at 50℃ was determined to be0.27. New elementary propagation reactions were proposed. On the basis of the propagation elementary reactions forcopolymerization with the participation of a charge-transfer complex (CTC), a method for measuring the reactivity ratios ispresented. Four reactivity ratios and relative reactivities of free monomer and CTC were obtained. They are r_(12)=0.034. r_(21)=0.012, r_(1C)=0.0030, r_(2C)=0.0034, and k_(1C)/k_(12)=11.34, k_(2C)/k_(21)=3.42.     

An alternating copolymer of maleimide and atropic acid with narrow molecular weight distribution prepared by radical mechanism

Three basic conditions for preparation of alternating copolymer with narrow molecular weight distribution were derived from the element kinetic equations of binary radical copolymerization. Using maleimide (MI) and atropie acid (ATA) as model monomer pairs and dioxane as the solvent the alternating copolymer with molecular weight distribution in the range of 1.09--1.20 was prepared successfully by charger transfer complex (CTC) mechanism in the presence of benzoyl peroxide at 85℃. The monomer reactivity ratioes r_1(MI)=0.05±0.01 and r_2(ATA)=0.03±0.02 were measured. The alternating eopolymerization was carried out through formation of a contact-type CTG and then alternating addition of MI and ATA monomers. The molecular weight of the copolymers is nearly independent of the feed ratio in a large range and the polymerization rate dropped with an increase in ATA in feed ratio.     

SYNTHESIS OF POLY(METHYL METHACRYLATE)-graft-POLYSTYRENE BY ATOM TRANSFER RADICAL POLYMERIZATION

The radical copolymerization of methyl methacrylate and 2-hydroxyethyl methacrylate was carried out via atomtransfer radical polymerization (ATRP) initiated by ethyl 2-bromoisobutyrate and catalyzed by CuBr/2,2'-bipyridinecomplex. This polymerization proceeds in a living fashion with controlled molecular weight and low polydispersity. Theobtained copolymer was esterified with 2-bromoisobutylryl bromide yielding a macroinitiator, poly(methyl methacrylate-co-2-hydroxyethyl methacrylate-co-2-(2-bromoisobutyryloxy)ethyl methacrylate), and its structure was characterized by ~1H-NMR. This macroinitiator was used for ATRP of styrene to synthesize poly(methyl methacrylate)-graft-polystyrene. Themolecular weight of graft copolymer increased with the monomer conversion, and the polydispersity remained relatively low.The individual grafted polystyrene chains were cleaved from the macroinitiator backbone by hydrolysis and the hydrolyzed product was characterized by ~1H-NMR and GPC.     

EFFECTS OF SOLVENT POLARITY ON FREE RADICAL COPOLY MERIZATION OF 5-HEXENOIC ACID AND ACRYLONITRILE

The effects of solvent polarity on free radical copolymerization of 5-hexenoie acid and acrylonitrile at 60℃ were studied. It was observed thatas the polarity of solvents enhanced, both the copolymcrization rate and the reactivity ratios r_1, r_2 increased, while the alternating tendency of monomer units in copolymer chain decreased. It is believed that the solvent polarity raises the reactivities of acrylonitrile monomer and its growing chain radical, but causes no distinct variation in those of 5-hexenoic acid.     

PREPARATION AND CHARACTERIZATION OF POLY[STYRENE-co-4-(2-PHENYLTHIOETHYLTHIOMETHYL)STYRENE]

Sulfur-containing monomers have received special interest from researchers because of their outstanding opticalperformance. Using the reaction between 2-phenylthioethyl-1-mercaptan and p-chloromethylstyrene, a new vinyl monomer4-(2-phenylthioethylthiomethyl)styrene (PTETMSt) was synthesized. Its structure was characterized by FT-IR and NMR.Copolymerization of styrene and PTETMSt was investigated. The data show that poly(styrene-co-PTETMSt) has higher refractive index, lower density and percentage of water absorption. The copolymer can be used on optical materials.     

Preparation of sulphonate-containing polymer particles <Emphasis Type="Italic">via</Emphasis> semi-continuous emulsion copolymerizaion of styrene and sodium styrene sulphonate

Submicron-sized P(St-NaSS) latexes were prepared via a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate(NaSS) in the presence of anionic surfactant,in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time.The hydrodynamic diameter of the latex particles was measured by dynamic light scattering(DSL) method,and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis.Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96%in the absence of crosslinker,and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h.The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge.The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol%DVB of total NaSS and St were used in the recipe,and the monomer feeding time was 3 h in copolymerization,the NaSS unit content of the purified copolymer reached 7.31 mol%.     

POLYMER-SUPPORTED RARE EARTH CATALYSTS FOR STYRENE POLYMERIZATION

The neodymium complex supported on styrene-maleic anhydride copolymer (SMA·Nd) has been prepared for the first time and found to be a highly effective catalyst for the polymerization of styrene. The SMA·Nd polymeric complex is characterized by IR and its catalytic activity, and the polymerization features have been investigated in comparison with that of the conventional Ziegler-Natta catalysts. When [Nd]=1×10~(-3) mol/L, [M]=5mol/L, Al/Nd=170(mol ratio) and CCl_4/Nd=50(mol ratio), the polymerization conversion of styrene gets to 51.6% in six hours, and the catalytic activity reaches 1852 gPS/gNd, which is much higher than that of conventional rare earth catalysts. The polymerization reaction has an induction period and shows some characteristics of chain polymerization. The polymerization rate is the first order with respect to the concentration of styrene monomer. Addition of FeCl_3 does not suppress the polymerization.     

COORDINATION COPOLYMERIZATION OF BUTADIENE AND ISOPRENE WITH RARE-EARTH CHLORIDE-ALCOHOL-ALUMINUM TRIALKYL CATALYTIC SYSTEMS

Butadiene and isoprene are copolymerized with LnCl_3-ROH-AlR_3 catalytic system. Theproducts obtained have been confirmed to be copolymers by its glass transition temperatureand characteristic pyrolytic chromatogram, etc. The equation of copolymerization rate may beexpressed as: R_p=K_p (M)~2(cat). The rate collstants of copolymerization, activation entrgyand monomer reactivity ratios for catalytic systems containing various rare earth elements inⅢ-B family and different solvents are determined. It has heen found that the reactivityratio of butadiene is greater than that of isoprene and r_1·r_2 near 1, and the composition andmicrostructure of copolymers are not much affected by variation of polymerization conditions.Both monomer units in the copolymer obtained have cis-1,4 content above 95%, which isthe distinguished feature of coordination lanthanide catalyst.     

Preparation of POE/PS blends with fine particle sizes by diffusion and subsequent polymerization of styrene in POE pellets

Ethylene-α-octene copolymer(POE)/polystyrene(PS) blend pellets with fine particle sizes were prepared by diffusion and subsequent polymerization of styrene in POE pellets through a one-pot procedure.The effects of the amounts of styrene and BPO on PS content,monomer efficiency and monomer conversion were investigated.The blend pellets were characterized by Micro-FTIR and FESEM,showing homogeneous diametrical distributions of PS and particle size.After melt-processing into rods,the average particle sizes are almost doubled,but still in submicron scale.Compared to neat POE rods,the blend rods with PS content higher than 15% exhibit improved tensile modulus and tensile strength without significantly losing ductility,being attributed to the small sizes,complex nature of particles and the existence of POE-g-PS copolymer that result in good interfacial adhesion.POE/PS pellets were compared with the previously reported PP/PS pellets,and the differences between the two systems are attributed to the different morphology of the two matrices: POE is completely amorphous at the diffusion and polymerization temperature,while i PP is semicrystalline.Without efficient impediment of the crystal lamellae in POE pellets,styrene diffuses easily in POE pellets.     

THE OVERALL KINETICS OF FREE RADICAL (CO)POLYMERIZATION WITH HIGHLY DIFFUSION CONTROLLED TERMINATION

The overall reaction rate kinetics of polymerization of diethyleneglycol dimethacrylate and copolymerization of it with styrene in bulk and in the presence of inert diluents were investigated. Theresults indicated that these reactions can be treated as free radical polymerization with highly diffu-sion controlled termination reaction in which the termination rate constant is an empirically derivedfunction of monomer conversion: K_t=K_(to)(1-c ln[M]/ [M_0])~(-1) in which K_(to) is the initial terminationrate constant and c is a factor related to the magnitude of diffusion co?re The following equationof monomer conversion as a function of time could then be derived: U=1-exp {1/c [1-(1+ckt/2)~2]}in which k=K_P(R_i/2K_(to))~(1/2) and t is the time of reaction. Excellent agreement between the theoreticaland experimental overall reaction kinetic curves was obtained. The equation is valid for crosslinkingand noncrosslinking free radical polymerizations in which the self-acceleration effcct is effective fromthe very beginning of the reaction. The equation can be expressed in a more generally applicableform: U=1--exp{1/e[1--(1+?t/n)~n] in which n≥0.     

n-Octyloxyallene homopolymerization and random copolymerization with styrene using catalyst system composed of lanthanide Schiff-base complexes and Al(i-Bu)3

The catalyst system composed of lanthanide Schiff-base complexes with [3,5-tBu2 -2-(O)C6H2 CH=NC6H5]3 Ln(THF)(Ln(Salen)3 , Ln = Sc, Y, La, Nd, Sm, Gd, Yb) and triisobutyl aluminum shows high activity for n-octyloxyallene (A) homopolymerization with narrow molecular weight distribution (MWD). The influences of reaction conditions on polymerization behavior are investigated, and poly(n-octyloxyallene) has a weight average molecular weight (M w ) of 20.6 × 10 3 with MWD of 1.39 and 100% yield is obtained under the optimum conditions: [Al]/[Y] = 50 mol/mol, [A]/[Y] = 100 mol/mol, with polymerization at 80 ℃ for 16 h in bulk. The kinetic studies of n-octyloxyallene homopolymerization indicate that the polymerization rate is first-order with respect to the monomer concentration and shows some controlled polymerization characteristics. Random copolymer of n-octyloxyallene with styrene is obtained by using the same binary catalyst system; the reactivity ratios of the comonomer determined by Kelen Tüd s method are r A = 1.20 and r St = 0.35, respectively, the ratio of each segment and M w of the resulting copolymer could be controlled by varying the feed ratio of each monomer. Determined by differential scanning calorimetry, the copolymers obtained show only one glass transition temperature, which increases gradually with the increase of styrene content in the copolymer.     

THE RELATION OF SEQUENCE DISTRIBUTIONS OF S-SBR TO ITS MOLECULAR WEIGHT DISTRIBUTIONS

The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li~+ as an initiator has been studied by ~(13)C-NMR,GPC. The results showed that the molecular weight distributions of the copolymer couldbe correlated sophisticatedly to the binary sequcne distributions or the monomer unit distributions of the copolymer in a corrected Poisson's distribution from.     

Electrosyntheses and characterization of a fluorescent conducting copolymer of benzanthrone and thiophene

<正>Poly(benzanthrone-co-thiophene),a new conducting copolymer,was successfully prepared by direct anodic oxidation of benzanthrone and thiophene(Th) in a binary solvent system containing boron trifluoride diethyl etherate (BFEE) and acetonitrile(ACN).The as-formed copolymer film electrodeposited with monomer feed ratio of benzanthrone/Th = 1:1 at the applied potential of 1.3 V versus Ag/AgCl exhibited the advantages of both polybenzanthrone and polythiophene,such as active electrochemical behavior,excellent thermal stability,relatively high electrical conductivity and mechanical properties.UV-Vis spectroscopy,~1H-NMR and SEM were used to characterize and investigate the structures and morphologies of the copolymers.Fluorescence spectroscopy studies revealed that the obtained copolymer films show strong emission at about 525 nm.Moreover,the emitting properties of the copolymers could be tuned by changing some parameters during the electropolymerization process,such as monomer feed ratio.     

Synthesis of novel biodegradable poly(ethylene glycol) analogue:Water-soluble aliphatic polyester with pendant oligo(ethylene glycol) chains

A novel poly(ethylene glycol)(PEG) analogue composed of aliphatic polyester backbone and pendant oligo(ethylene glycol) short chains is reported.The PEG analogue is a copolymer synthesized by ring-opening alternating copolymerization of succinic anhydride with 2-((2-(2-metho xyethoxy)ethoxy)methyl)oxirane.The structure of the copolymer was confirmed by ~1H NMR spectrum.The effects of the monomer feed ratio on the copolymerization were studied and the polymerization mechanism was given.The PEG analogue di...     

Copolymerization of α-Methylstyrene and Styrene

In this paper, the effects of temperature from 60 °C to 80 °C and the molar ratios in monomer feed on the copolymerization of α-methylstyrene(AMS) and styrene(St) were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75 °C, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St = 50/50(molar) in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as-AMS-AMS-AMS-,-St-AMS-AMS-(-AMS-AMS-St-) and-St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9 °C(0 mol% AMS) to 250.2 °C(42 mol% AMS). This behavior demonstrated that there exist weak bonds in the AMScontaining sequences which could be used as potential free radical generators.     

SYNTHESIS AND CHARACTERIZATION OF COPOLYMER OF 2,5-BIS[（4-METHOXYPHENYL）OXYCARBONYL]STYRENE AND STYRENE WITH HIGH MOLECULAR WEIGHT

The random copolymers of styrene and 2,5-bis[(4-methoxyphenyloxycarbonyl)styrene] (MPCS) with different copolymerization ratio were synthesized by conventional free radical polymerization. The copolymer having high molecular weight was experimentally elucidated using a combination of proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. The liquid crystalline behavior of the copolymer was studied using differential scanning calorimetry, X-ray diffractometry and polarized optical microscopy. It was found that the liquid crystalline behavior was dependent on the content of styrene. Experimental results show that the copolymer could turn into a liquid crystalline phase at about 180℃ when the content of styrene was less than 20%. The mechanical properties of the copolymer were also studied. Preliminary results indicate that the tensile strength decreases while the tensile modulus increases as the content of MPCS is increased.