Synthesis and characterization of cross-type vinylurethane macromonomer (C-VUM) and their application in the dispersion polymerization of styrene

The cross-type vinylurethane macromonomers (C-VUMs) were successfully synthesized using trimethylolpropane (TMP) as a cross-agent, and applied to the dispersion polymerization of styrene in ethanol. The existence and the structural identification of the reactants and the products were verified using the FT-IR and ¹H NMR spectra. The molecular weight of C-VUM increased, but the polydispersity index of C-VUM decreased with that of PEG. Structural verification of PS spheres synthesized from C-VUMs is carried out using ¹H NMR. However, the molecular weight of polyethylene glycol (PEG) in C-VUM does not affect the particle size of the PS particles, whereas enhanced the uniformity of the PS particles. Thus, C-VUMs act not only as reactive stabilizers, but also as grafting agents     

Poly(DL-lactide)/poly(ethylene glycol) copolymer particles. I. Preparation and characterization

In this study, poly(DL -lactide)/poly(ethylene glycol) (PDLLA/PEG) copolymers were synthesized. First, PDLLA homopolymers with three different molecular weights (Mw_n: 7,300, 12,100 and 21,900) were synthesized by the ring opening polymerization of the dimer (i.e., DL-lactide) by using stannous chloride as catalyst. Average molecular weights of PDLLAs were determined by gel permeation chromatography (GPC). They were characterized by Fourier transform infrared and differential scanning calorimetry (DSC). These PDLLA homopolymers were then transesterified with PEG with a molecular weight range of 3,300–4,000. By changing the ratio of PEG to PDLLA, block copolymers with different chain structures were synthesized. DSC and GPC studies were performed to characterize these PDLLA/PEG copolymers. PDLLA and PDLLA/PEG particles in the size range of 2–10 μm were prepared by a modified solvent evaporation technique by using methylene chloride as solvent and methyl cellulose as emulsifier within the aqueous dispersion medium. Particle size was controlled by changing the solvent/polymer ratio, PDLLA molecular weight, and PEG content. Degradation of polymeric particles was investigated in a phosphate buffer at pH 7.4 and at 37°C. Particles prepared with low-molecular-weight PDLLAs degraded much faster. Introduction of PEG within the polymeric matrix caused a pronounced increase in the degradation rate. Bulk degradation was the dominant mechanism. © 1996 John Wiley & Sons, Inc.     

Preparation and properties of amphoteric polyacrylamide by seeded dispersion polymerization in ammonium sulfate solution

Amphoteric polyacrylamide (AmPAM) was prepared successfully through seeded dispersion polymerization with acrylamide, methacrylatoethyl trimethyl ammonium chloride and acrylic acid as comonomers in ammonium sulfate solution. It was characterized by ¹H nuclear magnetic resonance (¹H NMR) and elemental analysis. The particle morphology and apparent viscosity of polymer dispersion were obtained by optical microscope and rotary viscometer, respectively. AmPAM dispersion was obtained with low apparent viscosity. The process was smooth without high viscosity stage. The data of ¹H NMR spectrum and elemental analysis indicated that all monomers had participated in the polymerization. The seeded reaction time and the mass ratio of two parts of monomers had significant effects on the dispersion polymerization. The best conditions were seeded reaction time 1.75h and the mass ratio 0.75. The apparent viscosity of AmPAM dispersion depended on the number of particles, particle size and low molecular weight polymer concentration in the continuous phase. AmPAM showed both anti‐polyelectrolyte effect and polyelectrolyte effect. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Radiation‐induced dispersion polymerization of methyl methacrylate using waterborne polyurethane as stabilizer

Waterborne polyurethane (WPU) without vinyl groups was synthesized and used as a stabilizer to prepare poly(methyl methacrylate) (PMMA) particles via dispersion polymerization with γ‐rays. The WPU molecular structure was characterized by Fourier transform infrared spectroscopy and ¹H NMR. PMMA particles were observed using scanning electron microscopy. The grafting reaction between PMMA and WPU was ascertained using ¹H NMR. Copyright © 2006 Society of Chemical Industry     

Synthesis of all-acrylic graft copolymers by grafting-through strategy in emulsion

In this paper, PnBA-g-PMMA brush-like and centipede multigraft copolymers were synthesized via DPE seeded emulsion polymerization and miniemulsion polymerization. PMMA macromonomers with single tail and double tails were prepared by DPE-technique in emulsion and Steglich esterification. Then PnBA-g-PMMA multigraft copolymers were obtained by miniemulsion copolymerization. The molecular weight and polydispersity indices of PMMA macromonomers and graft copolymers were characterized by GPC. The structural characteristics, weight content of PMMA and the number of grafting sites in brush-like and centipede multigraft copolymers were determined by ¹H NMR. The thermal performance of graft copolymers were analyzed by DSC and TGA. AFM confirmed microphase separation between PnBA block and PMMA block.     

Dispersion polymerization of acrylamide with 2-acrylamide-2-methyl-1-propane sulfonate in aqueous solution of sodium sulfate

The copolymer of acrylamide (AM) and 2-acrylamide-2-methyl-propane sulfonate (AMPS) was synthesized through free radical dispersion polymerization in an aqueous solution of ammonium sulfate and poly(2-acrylamide-2-methyl-1-propane sulfonate) as a steric stabilizer. The average particle size of the copolymer ranged from 1.0 μm to 4.0 μm, and the molecular weight was 2.0 × 10⁶ ~ 7.0 × 10⁶ g mol⁻¹. The swelling property of the dispersion copolymer was studied by characterizing the apparent viscosity and particle size distribution. When the dispersion was diluted with salt aqueous solution in which the ammonium sulfate concentration kept equal with that of the original dispersion, particle size and particle size distribution of the diluted dispersion changed little, compared with that of the original dispersion. While diluted with deionized water, particle size and particle size distribution could expand several times. The effects of the AMPS/AM molar ratios, the molecular weight of stabilizer, and the initiation temperature were investigated. It was found that with the increase of the AMPS/AM ratios, the molecular weight of copolymers increased, and then decreased. The particle size and conversion of monomers increased. The stability of the copolymer dispersion increased with increasing the molecular weight of stabilizer for a fixed stabilizer concentration. With the increase of the initiation temperature, the molecular weight of copolymer increased at first and then decreased gradually, but the particle size and conversion increased. The optimum conditions for the stable AMPS/AM dispersion were as follows: the AMPS/AM molecular ratio was 15/85, the molecular weight of the PAMPS stabilizer 3.0 × 10⁵ ~ 4.0 × 10⁵, and the initiation temperature 50 °С, respectively.     

Synthesis of polyethylene glycol-polystyrene core-shell structure particles in a plasma-fluidized bed reactor

Particles with core-shell structure with polystyrene (PS) core and polyethylene glycol (PEG) grafted on the surface were synthesized in a plasma-fluidized bed reactor. The virgin, plasma-treated, and grafted powders were characterized by the DPPH method, UV-vis spectrophotometer, NMR, FT-IR and SEM. The plasma-treated PS powders have well formed peroxide on the surface. By PEG grafting polymerization, PEG is well grafted and dispersed on the surface of the plasma-treated PS powders. The PEG-g-PS powder exhibits the core shell structure in the cross-sectional SEM image, and it can be claimed that well dispersed PEG grafting polymerization on PS surface can be achieved in the plasma fluidized bed reactor.     

Synthesis and characterization of comb‐like polymer PVC–poly(ethylene oxide)

A new series of amphiphilic graft‐copolymers, composed of poly(vinyl chloride) (PVC) backbones and poly(ethylene oxide) side chains, was synthesized by chemical modification of PVC. The synthesis was based on the reaction between chlorine in PVC (polymerization degree 700) and sodium salt of polyethylene glycol (PEG). PEGs with molecular weights of 200 and 600 were used. The graft polymers were characterized by IR and gel permeation chromatography and the molecular parameters such as the average numbers of grafting chains on the PVC backbones were calculated as well as the grafting percent. The molecular weights of PEG were found to influence the rate of the grafting reaction and the final degree of conversion. The maximum grafting percentage of the resulted polymers after the purification was ca. 34%, regardless of the molecular weight of PEG. No gel was observed in the PVC‐g‐PEOs, in spite of the average numbers of grafting chains up to 32. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 475–479, 2000     

Emulsion polymerization of tetrafluoroethylene: effects of reaction conditions on the polymerization rate and polymer molecular weight

The emulsion polymerization of tetrafluoroethylene (TFE) was carried out in a semibatch reactor using a chemical initiator (ammonium persulfate) and a fluorinated surfactant (FC-143). The effects of the reaction condition were investigated though the polymerization rate, molecular weight of polytetrafluoroethylene (PTFE), and stability of the dispersion. The emulsion polymerization of TFE was different from conventional emulsion polymerization. The polymerization rate was suppressed when the polymer particles were significantly coagulated. The polymerization rate increased with operating temperature, surfactant concentration, and agitation speed, due to the enhanced stability of the polymer particles. However, once the parameter value was reached, the rate decreased due to the coagulation of the particles. Stable PTFE dispersion particles were obtained when the surfactant concentration was in the range between 3.48 × 10⁻³ and 32.48 × 10⁻³ mol/liter, which is below critical micelle concentration (CMC). The molecular weight of the PTFE obtained was a function of the surfactant and initiator concentrations, and the polymerization temperature. The molecular weight increased as each parameter decreased. This is against the phenomena observed in a conventional emulsion polymerization. A stable PTFE dispersion polymer having a high molecular weight was obtained by optimizing the reaction conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 777–793, 1999     

Preparation and properties of nonionic polyol dispersion from terpinene‐maleic ester‐type epoxy resin

A nonionic epoxy‐based polyol (NTP) which can be used in place of the commonly used polyol dispersions to prepare two‐component waterborne polyurethanes was synthesized with terpinene‐maleic ester‐type epoxy resin (TME), polyethylene glycol (PEG), and trimethylopropane (TMP) in the presence of sulfuric acid as catalyst. The synthesis process was tracked with gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) by investigating the changes of molecular weight and glass transition temperature (T_g) of the product. FTIR was used to characterize the chemical structure of NTP. Major technical parameters of NTP were as follows: hydroxyl value 100 mg/g, hydroxyl group content 3.04%, T_g 4.03°C, and viscosity 150 mPa s (40% solid content). Effect of molecular weights and dosages of PEG on stability of NTP dispersion was examined by particle size analyses. It was found that stable dispersion was obtained when using PEG6000 as hydrophilic chain and its dosage ≥8% by the weight of TME. The average particle size of the prepared dispersion was about 200 nm from particles size and TEM analyses. The NTP dispersion showed characteristic of shear thinning, which indicated it was a pseudoplastic fluid. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthetic aspects and characterization of polypropylene-silica nanocomposites prepared via solid-state modification and sol-gel reactions

A new route is developed by combining solid-state modification (SSM) by grafting vinyl triethoxysilane (VTES) with a sol-gel method to prepare PP/silica nanocomposites with varying degree of adhesion between filler and matrix. VTES was grafted via SSM in porous PP particles. Bulk polymerization under similar experimental conditions as in SSM resulted in homopolymerization of VTES. However, SEC and NMR experiments showed that VTES was grafted as a single monomeric unit in the amorphous phase of PP with the possibility of VTES-polymer grafting during SSM. Silica-like nano-particles were synthesized in-situ by the sol-gel method. Magic-angle spinning (MAS) ²⁹Si NMR spectra showed that the chemical building blocks of the silica-like clusters are of Q³ and Q⁴ type. MAS ²⁹Si NMR and FT-IR spectroscopy showed that the grafted VTES becomes part of the in-situ formed silica particles. No decrease in molecular weight of PP was observed, indicating that chain scission is marginal compared to melt modification. The morphology of the nanocomposites as observed by ATR-FTIR microscopy showed a uniform dispersion of grafted VTES as well as in-situ formed silica. TEM and SEM demonstrated that the in-situ formed silica particles are nearly spherical and have sizes in the range of 50-100 nm.     

Reversible addition-fragmentation chain transfer polymerizations of styrene with two novel trithiocarbonates as RAFT agents

Two novel reversible addition-fragmentation chain transfer (RAFT) reagents bearing functional groups, S,S′-bis(9-anthrylmethyl) trithiocarbonate (BATTC) and S,S′-bis(1-naphthylmethyl) trithiocarbonate (BNTTC) were synthesized and used for the RAFT polymerizations of styrene (St). The polymerization results showed that the RAFT polymerizations could be well controlled using BNTTC or BATTC as the RAFT agents. For example, the polymerization rates were of first-order with respect to the monomer concentration, and the molecular weights of the obtained polystyrenes (PS) with narrow molecular weight distributions increased linearly with the monomer conversions and were close to their theoretical values in the presence of BNTTC or BATTC. The successful reaction of chain extension and analysis of ¹H NMR spectra confirmed the existence of the functional anthracene or naphthalene groups at the chain end of the correspondingly obtained PS. Optical properties of the obtained PS were characterized by fluorescence and UV absorption. Photochemical properties of the obtained PS end capped with anthracene were also described under irradiation of UV light.     

Dispersion polymerization of acrylamide with 2‐acrylamido‐2‐methyl‐1‐propane sulfonate in aqueous solution

The copolymer of acrylamide (AM) and 2‐acrylamido‐2‐methyl‐1‐propane sulfonate (AMPS) was synthesized through the free radical dispersion polymerization in an aqueous solution of ammonium sulfate and in the presence of poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonate) as stabilizer. The average particle size of the copolymer ranged from 1 to 4 μm, and the molecular weight was from 2.0 × 10⁶ to 7.0 × 10⁶ g mol^?1. By analyzing apparent viscosity and particle size, the swelling property of the dispersion copolymer was studied. When the dispersion was diluted with salt water in which the ammonium sulfate concentration kept equal with that of the original dispersion, particle size and particle size distribution of the diluted dispersion changed a little, compared with that of the original dispersion. While diluted with deionized water, particle size and particle size distribution could expand several times. The effects of varying concentrations of the stabilizer, the monomer, the salt and the initiator on particle size, and molecular weight of the copolymer were investigated, respectively. The reaction conditions for preparing stable dispersion were concentrations of 20–28% of the salt, 6–14% of monomers, and 1.8–2.7% of the stabilizer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2379–2385, 2006     

Preparation and application of partially porous poly(styrene‐divinylbenzene) particles for lipase immobilization

Partially porous poly(styrene‐divinylbenzene) (PS‐DVB) particles in the micron size range were prepared by the method of multistep swelling and polymerization involving the use of polymeric porogens. Polystyrene (PS) seeds prepared by dispersion polymerization were expanded in particle size by absorbing styrene and initiator, and then polymerized to form polymeric porogen particles. The newly synthesized PS chains served as the porogens of the PS‐DVB particles, resulting from the copolymerization of styrene and divinylbenzene in the swollen polymeric porogen particles. PS‐DVB particles with a specific surface area of up to 34 m²/g and a pore volume of up to 0.15 cm³/g were obtained. The average pore diameter of PS‐DVB particles was in the range of 15–24 nm. An increasing amount of toluene used in the copolymerization step increased the pore volume and specific surface area. Lipase from Candida rugosa was immobilized on the prepared PS‐DVB by physical adsorption. The optimum temperature for enzymatic activity was increased and the thermal deactivation of enzyme in organic solvent was slowed down by the immobilization. However, compared with soluble enzyme, the immobilized lipase on PS‐DVB retained a less activity after the first stage deactivation, suggesting a possible change in the conformation of enzyme molecule by immobilization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 39–46, 2001     

Dispersion polymerization of L-lactide in supercritical carbon dioxide

Triblock (A-B-A) oligomers of ε-caprolactone (ε-CL) (A) and poly(ethylene glycol) with an average molecular weight of 400 (PEG400) (B) were synthesized with three different molecular weight in the range of 2–6 kDa by changing the ratio of PEG400/ε-CL. These oligomers were then used in dispersion polymerization of L-lactide in supercritical carbon dioxide (scCO₂) as stabilizers. 5% stabilizer in the polymerization recipe allowed synthesis of poly(L-lactide) (PLLA) in scCO₂ in the powder form with a weight average molecular weight of around 60 kDa with polymerization yields around 80%. Interestingly, there was almost no effect of stabilizer molecular weight on polymerization. L-lactide polymerization in scCO₂ without any stabilizer was also possible but both the PLLA molecular weight and polymerization yield were lower, and the product was as aggregates instead of powders. A stabilizer concentration of 5% in the polymerization recipe was found adequate. Further increases in the stabilizer load resulted lower molecular weights and lower yields.     

Functional copolymers of p‐cumyl phenyl methacrylate and glycidyl methacrylate: Synthesis,characterization, and reactivity ratios

Free‐radical polymerization of p‐cumyl phenyl methacrylate (CPMA) was performed in benzene using bezoyl peroxide as an initiator at 80°C. The effect of time on the molecular weight was studied. Functional copolymers of CPMA and glycidyl methacrylate (GMA) with different feed ratios were synthesized by free‐radical polymerization in methyl ethyl ketone at 70°C, and they were characterized by FTIR and ¹H‐NMR spectroscopy. The molecular weights and polydispersity indexes of the polymers and copolymers were determined by gel permeation chromatography. The copolymer composition was determined by ¹H‐NMR. The glass‐transition temperature of the polymer and the copolymers was determined by differential scanning calorimetry. The reactivity ratios of the monomers were determined by the Fineman–Ross and Kelen–Tudos methods. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 336–347, 2005     

Effect of PVA in dispersion polymerization of MMA

Monodisperse poly(methylmethacrylate) microspheres having a diameter of 2.6 μm and a molecular weight of 102,277 g/mol with 5.3% of the C_v (the coefficient of variation) were synthesized by the dispersion polymerization using hydrophilic polyvinylalcohol (PVA) in methanol/water mixture media. Then, the structural verification of the synthesized materials is confirmed by using ¹H NMR and FT-IR spectroscopy. The effects of PVA and the polymerization parameters such as the initiator, monomer and stabilizer concentrations, and the reaction time on the characteristics of the final particles were studied. Thus, the role of PVA in the dispersion polymerization of MMA is not only a steric stabilizer by physically adsorbed in methanol phase, but also a colloid protective to give relatively monodisperse polymer particles in water phase, simultaneously.     

Free radical two step synthesis of styrene and acrylate block copolymers with disulphide initiators

Controlled two step block copolymerization of styrene, methyl methacrylate and ethyl acrylate with aliphatic and aromatic disulphides under UV irradiation took place in bulk and in THF solution. In the first step of the polymerization, the most reactive system was ethyl acrylate with aromatic disulphides. The molecular weights and yields of polymerizations increased with reaction time. The macromolecules were terminated by primary. SR radicals and by combination of two macroadicals which was observed by NMR spectroscopy. Aninsignificant portion of uninitiated photopolymerization was detected only for MMA. In the second step of polymerization, the purified macroinitiators from the first step reacted with additional monomers to form block copolymers with a small quantity of unreacted macroinitiator. The molecular weights of copolymers increased, the bonding segments between the blocks being detected by ¹H NMR. The overall reaction is an insertion of monomers between two thiyl groups.     

Strain-promoted azide-alkyne cycloaddition “click” as a conjugation tool for building topological polymers

Strain-promoted azide-alkyne cycloaddition “click” reaction (SPAAC) was successfully used as a tool in synthesis of star polymers by grafting onto approach. The application of SPAAC method in star polymer synthesis was investigated for coupling reaction of the dibenzocyclooctyne (DIBO) end group of polystyrene (PS) and poly(ethylene glycol) (PEG) with coupling agents bearing 2, 3, or 4 azido groups. Firstly, well-defined linear DIBO-terminated PS was obtained by atom transfer radical polymerization (ATRP) of styrene using a DIBO containing ATRP initiator and linear DIBO-terminated PEG was obtained by terminal functionalization of PEG monomethyl ether (PEG-OH). Then a series of star PS and PEG bearing two, three and four arms were prepared respectively by subjecting SPAAC coupling reaction between the linear polymer-DIBO and the azido tethered core molecules at 30 °C without catalyst. The obtained star PS showed a well-defined structure after fractional precipitation to remove slightly excess linear polymers, and all the star polymers were characterized via Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance spectroscopy (¹H NMR), size exclusion chromatography (SEC) and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS).     

Synthesis of side group liquid crystal-coil triblock copolymers with cyanobiphenyl moieties and PEG as coil segments by atom-transfer radical polymerization and their thermotropic phase behavior

Summary A series of side group liquid crystal-coil(SGLC-coil) triblock copolymers with narrow polydispersity was synthesized by atom transfer radical polymerization (ATRP), which was designed to have LC conformation of poly(11-(4′-cyanophenyl-4″-phenoxy)undecyl methacrylate) and coil-conformation of polyethylene glycol (PEG) (Mn=6000) segment. The SGLC block was prepared with a rang of molecular weights from 3.5×10³ to 1.4×10⁴. The macro-initiator PEG6000-Br was synthesized with PEG and 2-Bromo-2-methylpropionyl bromide by reaction of acid bromide. Their characterization was investigated using proton nuclear magnetic resonance (¹H NMR), Fourier Transform Infrared (FT-IR) spectra, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC) and polarized optical microscope (POM). All the block polymers exhibited a smectic A mesophase. The phase transition temperatures of the smectic to isotropic (T_S-T_I) phase increased and the crystallizability of PEG depressed with increasing of the molecular weight of the LC block. Received: 12 March 2002/Revised version: 25 April 2002/ Accepted: 30 April 2002