Model filled polymers. V. Synthesis of crosslinked monodisperse polymethacrylate beads

Monodisperse polymethacrylate beads of varied size and crosslink density are prepared by emulsion copolymerization of methacrylate and divinyl monomers in the absence of emulsifiers. The sizes of polybutyl and polyethyl methacrylate beads decreased with increasing polymerization temperature, while polymethyl methacrylate beads were largely unchanged in size. The molar mass of polymer in polymethyl metnacrylate beads markedly exceeded that in polystyrene beads. The rate of polymerization increased, and bead size decreased, with increasing initiator concentration or decreasing monomer concentration. The polymethacrylate beads are used as filler particles in polymer composites.     

Breaking embedded electrospun fibers (BEEF): Fabrication of polymer spheres encapsulated in polymer films

In this work, a novel method to fabricate polymer spheres encapsulated in polymer films by breaking embedded electrospun fibers (BEEF) was developed. Polymer fibers were first prepared by electrospinning and embedded in other polymer films using a three‐layer deposition method. After thermal annealing, the electrospun fibers transform into individual spheres with regular spacing and sizes. Poly(methyl methacrylate) (PMMA) and polystyrene (PS) are both used as the fiber or film materials. The transformation process can be observed in‐situ by optical microscope (OM) and is similar to the Plateau–Rayleigh instability. The growth rates of the surface undulation of the fibers are calculated, and higher growth rates are observed at higher annealing temperatures. The sizes of the encapsulated polymer spheres agree well with the theoretical predictions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2463–2470     

Copolymer with long chain alkyl group as stabilizer in the preparation of biodegradable polyester particle

Poly(eicosyl methacrylate‐co‐2‐hydroxyethyl methacrylate) is synthesized by free radical polymerization of eicosyl methacrylate and 2‐hydroxyethyl methacrylate by using 2,2′‐azobisisobutyronitrile as initiator in N,N‐dimethylformamide at 80°C. Copolymers of different molecular weights are synthesized and well characterized by different analytical techniques and used as a stabilizer in the preparation of polycaprolactone and polylactic acid particles by solvent evaporation method. The formation of the polymer particles and its morphology with respect to the stabilizer molecular weights, concentration, and reaction time are studied. Well dispersed poly(caprolactone) and poly(lactic acid) particles are formed, which demonstrated the efficiency of the copolymeric stabilizer. Polymer particle sizes and its stability depend on the molecular weights and concentration of the stabilizer. The surface morphology and particle sizes of the prepared particles are characterized by field emission scanning electron microscope.     

A fast convenient method to prepare hybrid sol-gel materials with low volume-shrinkages

We present a simple and fast method for the synthesis of polyacrylates-silica hybrid materials with significantly low volume shrinkages through the sol-gel reactions of tetraethyl orthosilicate and 2-hydroxyethyl methacrylate along with the free-radical polymerization of the acrylate monomer. The volume shrinkage from the processible sol to the final product was about 6–20% for the hybrid materials having the silica contents up to about 50 wt-%. As a result of the low shrinkage, crack-free, transparent and monolithic hybrid materials of relatively large sizes can be prepared within a short period of 6 to 12 hours. The formation of covalent bonding between the organic and the silica components in the hybrid materials was demonstrated. Thermal stability of the polyacrylate component in the hybrid materials were found to be higher than that of the bulk polymer. Other vinyl polymers such as poly(methyl methacrylate) and polyacrylonitrile have also been incorporated into the inorganic silica sol-gel matrix by using this method.     

Magnetic nanoparticles encapsulated latexes prepared with photo-initiated miniemulsion polymerization

This study describes the use of photo-initiated miniemulsion polymerization of methyl methacrylate and the incorporation of magnetic nanoparticles. With photo-initiator in the oil-in-water miniemulsion, UV irradiation led to the formation of polymer latexes after 15 min with the reaction temperature lower than 45 °C. Moreover, this method can be applied for the incorporation of magnetic nanoparticles. The particle sizes were measured by laser particle analyzer which showed narrow distributions. The morphology of the particles was examined with a transmission electron microscope and scanning electron microscope. The incorporation of magnetic nanoparticles was characterized with X-ray diffraction and vibrating sample magnetometer, both of which demonstrated that magnetic nanoparticles had been successfully incorporated into the polymer matrix.     

Development of Smart Polymer Microparticles through Suspension Polymerization for Treatment of Schistosomiasis

Schistosomiasis is a parasitic disease that affects millions of people, especially low‐income people, and is considered a major public health problem in underdeveloped countries. The drug used most often for the treatment of the disease is praziquantel (PZQ), which has a strong and characteristic bitter taste that makes treatment of children inconvenient. For this reason, the present work investigates the development of smart pH‐sensitive polymer microparticles produced through suspension polymerizations to be used as vehicles for the controlled release of praziquantel in the body. The microparticles are produced through copolymerization of methyl methacrylate and the cationic comonomers diethylaminoethyl methacrylate or dimethylaminoethyl methacrylate. The obtained results indicate that microparticles with sizes in the range of 10–1100 µm can be formed successfully, allowing high PZQ encapsulation efficiencies (>80%). Zeta potential analyses and drug release assays confirm the pH‐sensitive responses of the cationic copolymers, leading to effective release of PZQ (around 80% in pH 1.2) in acidic media that simulate the organic fluids present in the stomach.     

Synthesis,characterization and modeling of ABC triblock terpolymers: the effect of block sequence

Four equimolar terpolymers comprising ten units from each of the monomers methoxy hexa(ethylene glycol) methacrylate (HEGMA), 2-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) were prepared by group transfer polymerization (GTP), and characterized by gel permeation chromatography (GPC) and proton nuclear magnetic resonance (¹H NMR) spectroscopy to confirm size homogeneity and composition. These terpolymers were the three block sequence isomers, ABC, BAG and ACB, as well as the statistical isomer. Aqueous solutions of the terpolymers were characterized by dynamic light scattering and turbidimetry to determine the hydrodynamic sizes and cloud points. The results indicated micelle formation in the triblocks, and absence of micellization with the statistical terpolymer. In general, a strong dependence of the hydrodynamic size and cloud point on polymer architecture was observed. Monte Carlo simulations on non-aggregating isomeric terpolymers of similar structure also showed a strong dependence of the radius of gyration on polymer architecture.     

In Situ Incorporation of Praziquantel in Polymer Microparticles through Suspension Polymerization for Treatment of Schistosomiasis

Schistosomiasis is one of the major public health problems worldwide. Even though this is a common illness among preschool children in poor countries, treatment is carried out mainly through the administration of praziquantel tablets, which has some disadvantages, such as the strong bitter taste. As an alternative to overcome this problem, the development of new encapsulated praziquantel formulations is demanded. For this reason, suspension polymerizations are carried out for the in situ encapsulation of praziquantel into polymer microparticles, using methyl methacrylate (MMA) and cationic compounds (diethylaminoethyl methacrylate, DEAEMA, and dimethylaminoethyl methacrylate, DMAEMA) as comonomers. This technique allows for the preparation of polymer microparticles with high encapsulation efficiencies (>90%) with characteristic sizes ranging from 0.5 to 1500 µm. Drug release profiles show that praziquantel is released from poly(methyl methacrylate) microparticles slowly due to the existence of strong diffusional resistance. On the other hand, the addition of cationic comonomers renders polymer particles sensitive to pH variations, allowing for faster release of praziquantel in acidic environments, as found in the stomach.     

Kinetic study of the alternating copolymerization of butadiene and methyl methacrylate

A kinetic investigation of the alternating copolymerization of butadiene and methyl methacrylate with the use of a system of ethylaluminum dichloride and vanadyl chloride as a catalyst was undertaken. The relation between the polymer yield and the molar fraction of methyl methacrylate in the feed was examined by continuous variation of butadiene and methyl methacrylate, the concentrations of total monomer, ethylaluminum dichloride, and vanadyl chloride being kept constant. This continuous variation method revealed that the polymer yield attains its maximum value with a monomer feed containing less than the 0.5 molar fraction of methyl methacrylate. This value of the molar fraction of methyl methacrylate affording the maximum polymer yield decreased on increasing the total monomer concentration but was not changed on varying the concentration of ethylaluminum dichloride. The number of active species estimated from the relation between yield and molecular weight of the polymer was almost constant, regardless of the molar fraction of methyl methacrylate in the feed. Consequently, it can be said that the maximum polymer yield depends mainly on the propagation reaction, not on the initiation reaction or the termination reaction. Three types of the mechanism have been discussed for this alternating copolymerization: polymerization via alternating addition of butadiene and methyl methacrylate complexed with ethylaluminum dichloride by the Lewis-Mayo scheme; polymerization via the ternary intermediate of butadiene, methyl methacrylate, and ethylaluminum dichloride; polymerization via the complex formation of butadiene and methyl methacrylate complexed with ethylaluminum dichloride occurring only at the growing polymer radical. From the kinetic results obtained, it was shown that the first and third schemes are excluded, and polymerization by way of the ternary intermediate is compatible with the data.     

Miniemulsion polymerization of methyl methacrylate with dodecyl mercaptan as cosurfactant

Miniemulsions of methyl methacrylate with sodium lauryl sulfate as the surfactant and dodecyl mercaptan (DDM) as the cosurfactant (or hydrophobe) were prepared and polymerized. The emulsions were of a droplet size range common to miniemulsions and exhibited long-term stability (greater than 3 months). Results indicate that DDM retards Ostwald ripening and allows the production of stable miniemulsions. When these emulsions were initiated, particle formation occurred predominantly by monomer droplet nucleation. The effects of the concentration of surfactant, cosurfactant and initiator were determined. Rates of polymerization, monomer droplet sizes, polymer particle sizes, molecular weights of the polymer, and the effect of initiator concentration on the number of particles vary systematically in ways that indicate predominant droplet nucleation in these systems. © 1996 John Wiley & Sons, Inc.     

Polymerised bicontinuous microemulsions as stationary phases for capillary electrochromatography

Summary Polymerisation of bicontinuous microemulsions yields porous monolithic structures with well defined pore sizes that are potentially suitable for use as stationary phases for capillary electrochromatography (CEC). A variety of pore sizes can be achieved by altering the composition of the microemulsion, which typically consists of butyl methacrylate (BMA) and ethylene glycol dimethacrylate (EGDMA) as the polymerisable oil phase. The aqueous phase consists of water, a surfactant (sodium dodecyl sulphate, SDS) and a co-surfactant (1-propanol). 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) is also added to provide charges along the polymer backbone to allow electroosmotic flow (EOF) to occur. SEM analysis shows that in-situ polymerisation yields a monolithic structure with a porous topography. Investigations have shown that these monoliths are easy to prepare, robust and suitable for the separation of phthalates. They generate higher linear velocities than are achieved using the silica based HPLC packings normally used for CEC.     

Mathematical modeling of seeded miniemulsion copolymerization for oil-soluble initiator

A mathematical model of seeded miniemulsion copolymerization of styrene-methyl methacrylate for oil-soluble initiator is presented. The mathematical model includes the mass transfer, from the miniemulsion droplets to the polymer particles, by both molecular diffusion and collision between miniemulsion droplets and the polymer particles. The mathematical model also includes the calculation of both the distribution of partices with i radicals and the average number of radicals per particle in the miniemulsion copolymerization using oil-soluble initator. Studies were carried out on the mass transfer coefficients of monomers across the interface between the miniemulsion droplet and the aqueous phase, hexadecane concentration in the miniemulsion droplets, the miniemulsion droplet sizes, and the collision between miniemulsion droplets. The results indicated that the copolymerization of styrene-methyl methacrylate was not a mass transfer controlled process. The mass transfer by collision between miniemulsion droplets and polymer particles plays an important role and was included in the model in order to predict the experimental data of seeded miniemulsion copolymerization.     

Facile fabrication and self‐assembly of polystyrene–silica asymmetric colloid spheres

This study presents a very simple method to fabricate organic–inorganic asymmetric colloid spheres. In this approach, when silica particles are used as the Pickering emulsifier to stabilize the monomer droplets (styrene) in water via acid–base interaction between silica particles and auxiliary monomer (1‐vinylimidazole), the exposed surfaces of silica particles are very easy to be locally modified with 3‐(trimethoxysilyl)propyl methacrylate. When water‐based initiator is added, polystyrene–silica asymmetric colloid spheres are highly yielded. The sizes of silica and polymer particles can be tunable. These organic–inorganic anisotropic colloid spheres can self‐assemble into an interesting thickness‐dependent film. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Silica nanoparticle covered with mixed polymer brushes as Janus particles at water/oil interface

Silica nanoparticles (NSiO₂) are modified with mixed polymer brushes derived from a block copolymer precursor, poly(methyl methacrylate)-b-poly(glycidyl methacrylate)-b-poly(tert-butyl methacrylate) with short middle segment of PGMA, through one step ??grafting-onto?? approach. The block polymer precursors are prepared via reversible addition?Cfragmentation chain transfer-based polymerization of methyl methacrylate, glycidyl methacrylate, and tert-butyl methacrylate. The grafting is achieved by the reaction of epoxy group in short PGMA segment with silanol functionality of silica. After hydrolysis of poly(tert-butyl methacrylate) segment, amphiphilic NSiO₂ with ??V-shaped?? polymer brushes possessing exact 1:1 molar ratio of different arms were prepared. The functionalized particles self-assemble at oil/water interfaces to form stable large droplets with average diameter ranging from 0.15?±?0.06 to 2.6?±?0.75?mm. The amphiphilicity of the particles can be finely tuned by changing the relative lengths of poly(methyl methacrylate) and poly(methacrylic acid) segments, resulting in different assembly behavior. The method may serve as a general way to control the surface property of the particles.     

Lectin affinity chromatography using porous polymer monolith assisted nanoelectrospray MS/MS

An affinity porous polymer monolith is utilized as a nanoelectrospray emitter as well as an online affinity capture column for the preconcentration of glycans. Porous polymer monolith (PPM) assisted electrospray provides a facile methodology for coupling microfluidics to mass spectrometry that is sheathless and with zero dead volume. Affinity PPM was photopolymerized using glycidyl methacrylate/ethylene dimethacrylate utilizing different porogenic solvents based on aliphatic alcohols to provide PPMs with a variety of pore sizes. The use of longer alkyl chain alcohols decreased the pore size of the formed PPM as indicated by the higher flow back pressure generated. The effect of the pore size on the stability of the electrospray was tested showing higher stability of the TIC with lower pore size. A lectin, namely Concanavaline A, was immobilized on glycidyl methacrylate/ethylene dimethacrylate using the Schiff base method to provide an affinity monolith for high mannose glycans. The amount of the lectin immobilized was studied as a function of the porogenic solvent used in the polymerization. The glycopeptides of the glycoprotein Ribonuclease B was preconcentrated on the affinity PPM sprayer and detected by tandem MS.     

聚甲基丙烯酸-2,2,3,3-四氟丙酯的立构规整性

本文报道了由60℃自由基引发聚合得到的聚甲基丙烯酸-2,3,3-四氟丙酯,经浓硫酸水解而生成聚甲基丙烯酸。后者以重氮甲烷酯化,转化成聚甲基丙烯酸甲酯,并且分别作红外光谱、核磁共振波谱分析。根据分析结果推断聚甲基丙烯酸-2,2,3,3-四氟丙酯为无规立构聚合物,并与聚甲基丙烯酸正丙酯衍生而来的相应产物作比较。     

Design of Enzyme Micelles with Controllable Concavo‐Convex Micromorphologies for Highly Enhanced Stability and Catalytical Activity

Concavo‐convex micelles with controllable sizes and nanostructures are prepared via self‐assembling polymer–enzyme (e.g., shellac enzyme) conjugates with heterogeneous polymer chains, which exhibit higher enzyme stability (300%) and bioactivity (760%) comparing with the well‐defined ones. The applied amphiphilic and negatively charged copolymer, poly (methyl methacrylate)‐block‐poly (sodium p‐styrene sulfonate), is synthesized via reversible addition–fragmentation chain transfer polymerization to modify shellac enzyme and immobilize the enzyme bioactivity inducer by covalent conjugation and electrostatic attraction, respectively. The degradation test of catechol confirms the application potential of as‐prepared micelles as an efficient and economical decontaminant.     

Controlled functionalization of multiwalled carbon nanotubes by in situ atom transfer radical polymerization

The in situ ATRP (atom transfer radical polymerization) "grafting from" approach was successfully applied to graft poly(methyl methacrylate) (PMMA) onto the convex surfaces of multiwalled carbon nanotubes (MWNT). The thickness of the coated polymer layers can be conveniently controlled by the feed ratio of MMA to preliminarily functionalized MWNT (MWNT-Br). The resulting MWNT-based polymer brushes were characterized and confirmed with FTIR, 1H NMR, SEM, TEM, and TGA. Moreover, the approach has been extended to the copolymerization system, affording novel hybrid core-shell nanoobjects with MWNT as the core and amphiphilic poly(methyl methacrylate)-block-poly(hydroxyethyl methacrylate) (PMMA-b-PHEMA) as the shell. The approach presented here may open an avenue for exploring and preparing novel carbon nanotubes-based nanomaterials and molecular devices with tailor-made structure, architecture, and properties.     

Synthesis and characterization of polymethacrylate-based nitric oxide donors

A synthetic path for the preparation of methacrylic homo- and copolymers containing secondary amine groups that can be converted into nitric oxide (NO) releasing N-diazeniumdiolates is described. The polymers are obtained by a multistep procedure involving synthesis of methacrylate monomers containing boc-protected secondary amine sites, free radical benzoyl peroxide initiated polymerization, deprotection of the amine sites, and subsequent reaction of the polymers with NO in the presence of sodium methoxide. Monomers with both linear and cyclic pendant secondary amines are examined as polymer building blocks. In most cases, polymers are obtained for both types with compositions that agree well with initial monomer ratios and with number average molecular weights (M(n)) ranging from 1.69 to 2.58 x 10(6) Da. The final N-diazeniumdiolated methacrylic amine polymers are shown to release NO for extended periods of time with "apparent" t(1/2) values ranging from 30 to 60 min when suspended in phosphate buffer, pH 7.4. Total NO loading and release for these materials can reach 1.99 micromol per mg of polymer and is proportional to the amine content of the polymer. It is further shown that by using a dimethacrylate cross-linking agent in conjunction with the various methacrylate amines, suspension polymerization methods can be employed to create small (100-200 microm) polymeric methacrylate microbeads. Such microbeads that can be sequentially deprotected and converted to NO release particles via in-situ diazeniumdiolate formation as carried out for the non-crosslinked polymers.     

A versatile method for tuning the chemistry and size of nanoscopic features by living free radical polymerization

A novel approach is presented for manipulating the size and chemistry of nanoscopic features using a combination of contact molding and living free radical polymerization. In this approach a highly cross-linked photopolymer, based on a methacrylate/acrylate mixture, was patterned into submicrometer-sized features on a silicon wafer using a contact-molding technique. A critical component of the monomer mixture was the incorporation of an initiator containing monomer into the network structure, which provides sites for functional group amplification. Features ranging in size from 5 microm to <60 nm were accurately replicated by this process and living free radical polymerizations, both atom transfer radical and nitroxide-mediated polymerization (NMP), could be conducted from these initiating sites to yield polymer brushes which represent a grafted layer of linear chains attached to the original network polymer. Grafts consisting of polystyrene, poly(methyl methacrylate), and poly(2-hydroxyethyl)methacrylate were grown with controlled thicknesses ranging from 10 to 143 nm and graft molecular weights of between 18 000 to 290 000 amu. As a result of this secondary graft process, feature sizes could be tuned from the original 100 nm down to 20 nm, and the surface chemistry varied from hydrophilic to hydrophobic starting from the same initial master pattern. The thin films and patterned features were characterized by contact angle, ellipsometry, optical, and atomic force microscopies.