Kinetics of polymerization and particle stabilization mechanism on dispersion copolymerization of styrene and divinylbenzene

Monodisperse highly crosslinked microspheres were prepared by dispersion copolymerization of styrene and divinylbenzene in an ethanol/water medium using poly(N‐vinylpyrrolidone) (PVP) as the stabilizer. The locus of polymerization and growth of particles were investigated. The polymerization kinetics, average particle diameter (D_n), polydispersity index (PDI), and numbers of particles (N_p) were presented. When the initial styrene concentration is below 20%, the results indicate that the polymerization occurs in the particles, and the particles grow to their final size by the diffusion of monomer and oligomer into the existing particles. The polymerization rate can be described by the equation R_p = k[l]^0.87 ([St]^1.91 + [DVB]^0.09) (1 + [PVP]^0.01) exp(? 45.35/RT). The data from infrared spectroscopy demonstrated that the graft stabilizer was present. The dissolution experiments show that the crosslinking reaction occurred irregularly in batch dispersion polymerization. Using the postaddition approach, up to 3% divenylbenzene (DVB) was successfully incorporated in the synthesis of coagulum‐free substance, and monodisperse crosslinked 5 μ m microspheres with a superior resistance to solvents have been prepared. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2230–2238, 2002     

混悬型滴眼液中助悬剂的应用

介绍了混悬型滴眼液中助悬剂的作用及种类,以及几种常见助悬剂的特点及应用,在研制混悬型滴眼液时选择合适的助悬剂。     

Thermophysical and mechanical properties of novel polymers prepared by the cationic copolymerization of fish oils, styrene and divinylbenzene

New polymeric materials have been prepared from the cationic copolymerization of fish oil ethyl ester (NFO), conjugated fish oil ethyl ester (CFO) or triglyceride fish oil (TFO) with styrene and divinylbenzene initiated by boron trifluoride diethyl etherate (BF₃·OEt₂). These materials are typical thermosetting polymers with crosslink densities ranging from 1.1×10² to 2.5×10³ mol/m³. The thermogravimetric analysis of the new fish oil polymers exhibits three distinct decomposition stages at 200–340, 340–500 and >500°C, respectively, with the maximum weight loss rate at approximately 450°C. Single glass-transition temperatures of T_g=30–109°C have been obtained for the fish oil polymers. As expected, these new polymeric materials exhibit tensile stress–strain behavior ranging from soft rubbers through ductile to relatively brittle plastics. The Young's modulus (E) of these materials varies from 2 to 870 MPa, the ultimate tensile strength (σ_b) varies from 0.4 to 42.6 MPa, and the percent elongation at break (ε_b) varies from 2 to 160%. The failure topography indicates typical fracture mechanisms of rigid thermosets, and the unique fibrillation on the fracture surface gives rise to relatively high mechanical properties for the corresponding NFO polymer. The new fish oil polymers not only exhibit thermophysical and mechanical properties comparable to petroleum-based rubbery materials and conventional plastics, but also possess more valuable properties, such as good damping and shape memory behavior, which most petroleum-based polymers do not possess, suggesting numerous, more promising applications of these novel fish oil-based polymeric materials.     

Synthesis and characterization of reactive macroporous poly(glycidyl methacrylate‐triallyl isocyanurate‐ethylene glycol dimethacrylate) microspheres by suspension polymerization: Effect of synthesis variables on surface area and porosity

A novel macroporous poly(glycidyl methacrylate‐triallyl isocyanurate‐ethyleneglycol dimethacrylate) copolymer, hereinafter P_{GMA‐TAIC‐EGDMA}, of controlled bead size was prepared via free radical suspension copolymerization. The effects of varying the concentration of crosslinking agents and porogenic diluent on the average pore diameter, pore size distributions, specific surface area, and pore volume of the copolymer matrix were thoroughly investigated. The spherical beads were characterized by elemental analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The specific pore volume, average pore diameter, pore size distribution, and the specific surface area were measured by Mercury intrusion porosimetry and BET adsorption method, respectively. The porous properties of the polymer matrix are a direct consequence of the amount and quality of the porogenic solvent, the percentage of crosslinking monomers, and the ratio between the monomers and porogen phases. When the polymer was prepared at 30 and 40% crosslinking density, and 75 and 100% diluents, respectively, it showed a fine beads morphology, mechanical stability and pore size distributions. By comparing the copolymers P_{GMA‐TAIC‐EGDMA} and P_GMA‐EGDMA, it was found that the former is more stable both thermally and mechanically than its predecessor. The presence of epoxide functionalities of macroporous P_{GMA‐TAIC‐EGDMA} beads makes it a versatile carrier. The resulting polymers have the potential for wide applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis of amphiphilic microspheres by suspension copolymerization of styrene and poly(ethylene oxide) macromonomer

Amphiphilic microspheres, ranging in size from 3 to 35 μm, were prepared by suspension copolymerization of styrene with poly(ethylene oxide) vinylbenzyl (PEO–VB) macromonomer by changing polymerization conditions. It was found that an increase in the amount of dispersant and the PEO–VB concentration resulted in decreases of the size and size distribution of amphiphilic microspheres. The morphology, size, and size distribution of amphiphilic microspheres were characterized by scanning electron microscopy. The structure of copolymer was confirmed by infrared spectroscopy, differential scanning calorimetry, elemental analysis, and X‐ray photoelectron spectroscopy. The content of the hydroxyl groups localized in the microspheres ranged from 0.05 to 0.2 mmol/g. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 333–339, 2001     

A kinetic investigation of styrene/butyl acrylate copolymerization

An experimental investigation of the kinetics of the bulk free radical copolymerization of styrene/butyl acrylate initiated with 2,2′-azobisisobutyronitrile (AIBN) was conducted at 50°C using various initiator concentrations and initial monomer ratios including the azeotropic composition. Reactivity ratios were determined by analyzing composition data using the error-in-variables model. The experiments, designed using the Tidwell-Mortimer criterion, were conducted in sealed ampoules at 50°C to low conversion levels (< 7%). From the calculated reactivity ratios, the azeotropic composition was determined and further experiments were run at these conditions as well as at two other initial monomer feed compositions in order to collect composition, rate and molecular weight data. The experiments were run through the full conversion range at two different initiator concentrations.     

N-丁基马来酰亚胺/苯乙烯共聚合机理研究

研究了氘代氯仿中Ｎ－丁基马来酰亚胺（ＮＢＭＩ）和苯乙烯的络合性能。在多组分Ｏ／Ｗ微乳液中,用过硫酸钾引发ＮＢＭＩ和Ｓｔ进行微乳液共聚合,考察了聚合温度,单体配比对共聚合的影响,并对共聚机理进行了研究。结果表明,ＮＢＭＩ／Ｓｔ微乳液共聚合是按照自由－络合机理进行的,在共聚合过程中,既有自由单体参与,又有电荷转移络合物（ＣＴＣ）参与。     

Preparation of macroporous,monodisperse, functionalized styrene–divinylbenzene copolymer beads: Effect of the nature of the monomers and total porogen volume on the porous properties

The staged templated suspension polymerization method was used for the preparation of 5 μm beads from mixtures of styrene and several substituted styrene monomers, including 4-methylstyrene, 4-aminostyrene, 3-aminostyrene, 4-acetoxystyrene, and 4-tert-butoxycarbonyl oxystyrene, with divinylbenzene in the presence of various amounts of linear polystyrene and dibutyl phthalate as porogens. The nature of the monomer as well as the total percentage of porogenic compounds in the polymerization mixture have a large effect on the porous properties and surface morphology of the monodisperse beads. Beads with large pores can only be obtained once the percentage of porogen in the mixture exceeds a threshold value that varies with the type of monomers involved in the polymerization. The level of incompatibility of the functional polymer chains formed during the crosslinking polymerization with the linear polystyrene porogen that is present in the polymerization mixture is another variable that also affects both the porous properties and the morphology of the beads. Because better compatibility is achieved, this effect is less pronounced if unfunctionalized styrene is used as a monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 597–607, 1998     

Continuous thermal bulk copolymerization of styrene and maleic anhydride

Thermal bulk copolymerization of styrene (monomer 1) and maleic anhydride (monomer 2) was carried out in a continuous stirred tank reactor (CSTR) with a double helical ribbon-anchor impeller. A series of experimental runs under different operating conditions (average residence time, reaction temperature, and the composition in the inflow stream) were done, which showed that steady states could be approached. The effect of operating conditions on monomer conversion and copolymer composition was discussed. A CSTR model was established and the model parameters from the semicontinuous tests were used to predict conversions and copolymer compositions of the continuous process under transient and steady states. Kinetics from the semicontinuous bulk copolymerization were transferable to the continuous process. The modeling work for the continuous process showed that the same result as in a semicontinuous process could be obtained; the numerical method in which the gel effect on the copolymerization was incorporated exhibited excellent agreement between the model calculation and the experimental data. However, when using the assumption that k₂₂ = 0, k₂₁[M₁] ≫ k₁₂[M₂], (R_I/2k_t)^1/2 is a constant, and V is a constant, the predictions from the analytical solution to the model were in good agreement with the actual process data. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 615–622, 1999     

Bulk copolymerization of styrene and acrylonitrile: Experimental kinetics and mathematical modelling

The kinetics of styrene-acrylonitrile bulk copolymerization have been experimentally investigated over a wide range of conditions. The effects of temperature, and initiator and of comonomer concentrations on rate of polymerization and on copolymer properties including chain microstructure and molecular weight averages are reported. A mathematical model which uses the free volume theory to account for diffusion controlled termination and propagation reactions is developed. The model is capable of predicting the conversion, composition and sequence length development up to limiting conversions.     

Radical copolymerization behaviors of styrene and coumarin

The radical copolymerizations of styrene (M₁) with coumarin (M₂) (and 7-acetoxycoumarin) have been first carried out in benzene (and in DMF) at 60° C using AIBN as initiator. The terminal model monomer reactivity ratios (MRR) were determined by Fineman-Ross method, Kelen-Tudos method and nonlinear method. The respective estimated values are r₁ = 43.08, r₂ = 0.63; r₁ = 39.17, r₂ = 0.43; and r₁ = 49.94, r₂ = 1.04 for styrene-coumarin (S-C) system. For styrene-7-acetoxycoumarin (S-AC) system, the values are r₁ = 51.44, r₂ = 1.24; r₁ = 50.56, r₂ = 1.20 and r₁ = 56.23, r₂ = 1.48, respectively. The penultimate model MRRs are determined by Fenn-Barson method and nonlinear method to be r₁= 49.18, r₁ = 2.01, r₂ = r₂ = 0.43 and r₁ = 51.21, r₁ = 0.86, r₂= r₂ =0, respectively, for S-C system; r₁ = 64.76, r₁= 3.46, r₂ = r₂= 1.20 and r₁ = 59.90, r₁ = 0.57, r₂ = r₂ = 0. respectively, for S-AC system. It is found that coumarin is about 1.2 times more reactive toward styrene-terminated radical than 7-acetoxycoumarin for steric reasons. The penultimate model of Fenn-Barson is fairly adequate in describing the copolymerization mechanism of styrene-coumarin system, while the terminal model is more suitable for styrene-7-acetoxycoumarin system.     

Soybean and castor oil based monomers: Synthesis and copolymerization with styrene

In this study, castor oil was alcoholyzed with both aliphatic alcohols, such as glycerol and pentaerythritol, and an aromatic alcohol, bisphenol A propoxylate. The resulting alcoholysis products were then malinated and cured in the presence of styrene. Soybean oil pentaerythritol glyceride maleates were also prepared for a direct comparison of the properties of the castor oil and soybean oil based resins. Castor oil was directly malinated as well to see the effect of the alcoholysis step on the properties of the castor oil based resins. The monomers synthesized were characterized by ¹H‐NMR spectroscopy, and the styrenated resin liquid properties, such as viscosity and surface energy values, were determined. The conversion of polymerization was determined using time resolved FTIR analysis for the styrenated soybean oil pentaerythritol glyceride maleates, castor oil maleates, and castor oil pentaerythritol glyceride maleates. The effect of monomer identity and styrene content on the conversion of polymerization was explored. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2433–2447, 2006     

Particle size control in suspension copolymerization of styrene,chloromethylstyrene, and divinylbenzene

The particle size distribution of suspension copolymers of styrene, chloromethylstyrene, and divinylbenzene prepared with gelatin and poly(diallyldimethylammonium chloride) as suspension stabilizers can be varied widely by variation of the relative amounts of monomer and aqueous phases, the stirring speed, and the amount of added anionic surfactant sodium dodecylbenzenesulfonate.     

Graft copolymerization of styrene and acrylonitrile onto EPDM

Acrylonitrile–EPDM–styrene (AES) graft copolymers were synthesized by solution graft polymerization of styrene (St) and acrylonitrile (AN) onto EPDM in an n‐hexane/benzene solvent with benzoyl peroxide (BPO) as an initiator. The structure changes were studied by an FTIR spectrophotometer. The grafting parameters were calculated gravimetrically. The influence of the polymerization conditions, such as the reaction time, concentration of the initiator, EPDM content, and weight ratio of St/AN, on the structure of the products was investigated. It was found that a proper initiator concentration and EPDM content will give a high grafting ratio of the AES resin. The thermal property of the copolymer was studied using programmed thermogravimetric analysis (TGA). The results showed that the copolymer has a better heat‐resistant property than that of ABS, especially for the initial decomposition temperature (T_in) and the maximum weight loss rate temperature (T_max). Also, the mechanism of the graft reaction was discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 428–432, 2002     

苯乙烯/N-丁基马来酰亚胺共聚合研究

以偶氮二异丁腈为引发剂,采用溶液聚合法合成了苯乙烯/N-丁基马来酰亚胺共聚物.详细研究了聚合温度、引发剂用量、单体配比对共聚合动力学的影响,并对共聚机理进行了初步探讨.     

Study on suspension copolymerization rate of vinyl chloride/N-phenylmaleimide

The copolymerization rate of vinyl chloride(VC)/N-phenylmaleimide (PMI) was investigated. The cross termination constant φ was measured to be 8.3 by using nonlinear least square fitting. The value showed that the cross termination was significant. A model of the copolymerization rate of VC/PMI was obtained. Using the calculated modeling parameters, the effects of temperature and initiator concentration on the copolymerization rate were predicted. The predicted values were in good agreement with the experimental data. Acrylonitrile, a third monomer, was selected to reduce the range of copolymer composition of this system, but it further lowered the copolymerization rate. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2649–2656, 1999     

Spectral characterization and thermal behaviour of crosslinked poly(hydroxyethylmethacrylate) beads prepared by suspension polymerization

Crosslinked poly(hydroxyethylmethacrylate) [poly(HEMA)] beads were prepared by the suspension copolymerization of 2-hydroxyethylmethacrylate monomer with ethyleneglycol dimethacrylate (EGDMA) in aqueous media which contained only magnesium oxide (MgO) as a suspension stabilizer and also salting-out agent. The procedure gives spherical particles with narrow size distribution. The reaction mechanism, composition and structure of poly(HEMA) beads were studied by solid-state ¹³C CP/MAS NMR, FTIR, ESCA, and elemental analysis. ¹³C NMR implies the existence of unreacted pendant groups in the HEMA-EGDMA copolymer. The surface composition obtained by ESCA is almost the same as the bulk composition determined by elemental analysis. FTIR spectra provide compelling evidence for the presence of carboxyl and hydroxyl groups. The glass-transition temperature and the thermal stability of beads were determined by DSC.     

Photoinitiated copolymerization of acrylamide and styrene in oil-in-water microemulsion

This article describes the copolymerization of acrylamide with styrene in oil-in-water microemulsion, using dodecyl betaine as emulsifier and α-hydroxy-α,α-dimethyl acetophenone or α,α-dimethoxy-phenyl acetophenone as photoinitiator. Results indicated that the photoinitiation of polymerization occurs at the interface between the oil phase and the water phase and that the polymerization occurs in the microemulsion droplet. Particle size increased with increasing polymerization time. The copolymer chain consisted of isolated acrylamide units randomly distributed among styrene groups. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2543–2549, 1997     

Pore architectures and oil absorption behavior of porous mullite beads fabricated via dripping-ice templating

Porous mullite beads with a good spherical shape and a uniform size distribution of about 1.2 mm were fabricated by ice-templating in combination with dripping methods. These internal pore structures exhibited a radially oriented laminar channel from the center of the sphere to the surface. With the decreasing of freeze temperature to −196°C, the thickness of pore walls and the width of pore decreased. The mullite grain morphology in the pore wall was also influenced by the frozen temperature. High aspect ratio mullite grain was formed in the pore wall of beads frozen at −25°C, while low aspect ratio mullite whiskers constituted the pore wall of beads frozen at −196°C. In addition, the obtained porous mullite beads exhibited a good oil adsorption performance under capillary force for kerosene, edible oil, and motor oil with adsorption values of 3.37, 4.07, and 4.04 g/g, respectively.