Free Radical Copolymerization Of Styrene Research Articles

Cross-linked polymer microparticles with tunable surface properties by the combination of suspension free radical copolymerization and Click chemistry

We propose a general, versatile and broad in scope two-steps approach for the elaboration of cross-linked polymer microparticles (µPs) with tunable functionalities and surface properties. Surface-functionalized cross-linked polymer µPs with diameter in the 80 μm range are prepared by the combination of: 1) suspension free radical copolymerization of styrene, propargyl methacrylate and 1,6-hexanediol dimethacrylate, 2) subsequent covalent tethering of a variety of azide-functionalized moieties (i.e. rhodamine B fluorescent dye or poly(ethylene glycol) (PEG) brush precursor) by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and, 3) optional N-alkylation of the 1,2,3-triazole groups followed by anion exchange reaction to afford covalently-tethered 1,2,3-triazolium ionic liquids with iodide or cresol red counter-anions. The resulting µPs are characterized by laser diffraction, differential scanning calorimetry, as well as by optical, confocal fluorescence, scanning electron and atomic force microscopies. Finally, the rheological properties of concentrated suspensions (volume fractions of 0.40 and 0.44) of the different synthesized µPs dispersed in a 1:1 (vol/vol) mixture of polyalkylene glycol and water are studied. The modification of µPs surface properties contributes not only to change the stability of the suspensions against flocculation, but also to significantly modify their rheological behavior at high shear stresses. This represents a clear experimental evidence of the importance of non-hydrodynamic contact forces in the rheology of non-Brownian suspensions (NBSs).

Facile synthesis of reversibly crosslinked poly(ionic liquid)-type gels: Recyclable supports for organocatalysis by N-heterocyclic carbenes

Owing to their broad modularity, polymeric versions of ionic liquids, referred to as poly(ionic liquids) (PILs), have attracted increasing attention as recyclable polymer-supported (pre)catalysts for various chemical transformations. Herein, an imidazolium-based statistical copolymer based on PIL (=coPIL) is specifically designed by free-radical copolymerization of styrene and 4-vinylbenzylethyl(benz)imidazolium chloride. A selective ion-exchange reaction can be subsequently achieved to incorporate bio-sourced difunctional sebacate-type counter-anions, causing the physical crosslinking of the coPIL precursor via electrostatic interactions between pendant imidazolium moieties and sebacate dianions. The as-obtained gel-type precursor exhibits a thermally latent behavior in THF, proving advantageous for a facile manipulation and practical use for organocatalysis. Upon heating, typically at 80 °C, interaction between the sebacate dianion and the proton in C2-position of the imidazolium moieties generates polymer-supported N-heterocyclic carbene units that act as catalytic active species towards NHC-organocatalyzed reactions, namely, benzoin condensation, transesterification and cyanosilylation. The PIL-based gel precursors can be restored, recycled and reused by simply cooling down, i.e. with no need of an external chemical reagent, due to the shift of the intramolecular equilibrium towards the formation of imidazolium sebacate-type units. Overall, this novel gel-type copolymeric platform shows a thermo-responsive behaviour, and proves particularly versatile for heterogeneous organocatalysis.

Construction of a Different Polymer Chain Structure to Study π-π Interaction between Polymer and Reduced Graphene Oxide.

In this work, a different polymer chain structure was synthesized to study π-π interactions between polymer and reduced graphene oxide (RGO). Polymers with different chain structures were obtained from free radical copolymerization of styrene with 4-cyanostyrene (containing substituted phenyl rings) and 2-vinylnaphthalene (containing naphthalene rings). In this work, the polystyrene, poly(styrene-co-4-cyanostyrene) and poly(styrene-co-2-vinylnaphthalene) were named as PS, PSCN and PSNP, respectively. RGO was prepared through modified Hummers’ method and further thermal reduction, and nanocomposites were prepared by solution blending. Thus, different π-π interactions were formed between polymers and RGO. Raman and thermal gravimetric analysis (TGA) were used to characterize the interfacial interaction, showing that the trend of the interfacial interaction should be in the order of RGO/PSCN, RGO/PS, and RGO/PSNP. The differential scanning calorimetry (DSC) measurement showed that, compared with polymer matrix, the glass transition temperature (Tg) of RGO/PS, RGO/PSCN and RGO/PSNP nanocomposites with the addition of 4.0 wt% RGO are increased by 14.3 °C, 25.2 °C and 4.4 °C, respectively. Compared with π-π interaction only formed through aromatic rings, substituent groups changed the densities of electron clouds on the phenyl rings. This change resulted in the formation of donor-acceptor interaction and reinforcement of the π-π interaction at the interface, which leads to increased value of Tg. This comparative study can be useful for selecting appropriate interaction groups, as well as suitable monomers, to prepare high performance nanocomposites.

Controlling of free radical copolymerization of styrene and maleic anhydride via RAFT process for the preparation of acetaminophen drug conjugates

The presence of maleic anhydride moiety in styrene-maleic anhydride (SMA) copolymer makes it a versatile substrate for conjugation of drugs. In this study biocompatible styrene-maleic anhydride (SMA) copolymer with alternating structure was synthesized by gamma irradiation at room temperature in the presence of 2-phenyl-2-propyl benzodithioate (PPB). The poly(styrene-alt-maleic anhydride) (poly(St-alt-MA)) with narrow molecular weight distribution (Đ: 1.1–1.3) was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The synthesized poly(St-alt-MA) structure was characterized by ATR-FTIR spectroscopy, elemental analysis and 1H NMR spectroscopy and molecular weight and dispersity were determined by size exclusion chromatography (SEC). SMA copolymers were further conjugated with acetaminophen via ester linkage and FT-IR, 1H NMR investigation indicated that the acetaminophen was attached to poly(St-alt-MA). Drug release profile of the polymer-drug conjugate was followed by high performance liquid chromatography (HPLC). The drug-conjugate system was found to follow first order release kinetics with Hixson-Crowell model while drug release mechanism was found as non-Fickian diffusion after testing various kinetic models.

Syntheses and luminescent properties of a copolymer of terbium-p-aminobenzoic acid-methacrylic acid and styrene.

A reactive Tb(III) complex with p-aminobenzoic acid (p-ABA) and methacrylic acid (MAA) as ligands was synthesized. A novel copolymer was synthesized by free radical copolymerization of styrene and the reactive Tb(III) complex in dimethyl sulfoxide (DMSO) with 2,2'-azobis(2-methylpropionitrile) (AIBN) as the initiator. IR and UV/Vis spectra indicate that the copolymer exhibited absorption from polystyrene and the complex. Thermogravimetric analysis indicates that the copolymer remained stable up to 357°C and the thermal stability was significantly improved in comparison with polymer matrix and the Tb(III) complex. The luminescent intensity of the synthetic terbium macromolecular complexes increased with increasing complex monomer content. Moreover, concentration quenching was not observed.

Solvent effects on free-radical copolymerization of styrene and 2-hydroxyethyl methacrylate: a DFT study

The free-radical homopolymerization and copolymerization kinetics of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, DMF, toluene) have been investigated by means of Density Functional Theory (DFT) calculations in combination with the Polarizable Continuum Model (PCM) and the Conductor-like Screening Model for Real Solvents (COSMO-RS). The conventional Transition State Theory (TST) is applied to calculate the rate parameters of polymerization. Calculated propagation rate constants are used to predict the monomer reactivity ratios, which are then used in the evaluation of the copolymer composition following the Mayo–Lewis equation. It is found that copolymerization reactions in bulk and toluene show similar transition geometries; whereas, DMF has a tendency to form H-bonding interactions with the polar HEMA molecules, thus decreasing the reactivity of this monomer during homopolymerization and towards ST during copolymerization. Calculations of copolymer composition further show that the amount of HEMA monomer in the ST–HEMA copolymer system decreases in the polar DMF solution. The calculated spin densities of the radical species are in agreement with the rate parameters and confirm that the copolymerization propagation rate of the ST–HEMA system is in the order: kp(bulk) ≈ kp(toluene) > kp(DMF).

Free-radical polymerization induced macrophase separation in poly(methyl methacrylate)/dimethacrylate blends: Experiment and modeling

This work presents the analysis of a polymerization-induced macrophase separation taking place during free-radical copolymerization of styrene and dimethacrylate in the presence of poly(methyl methacrylate) (PMMA) as a modifier. The PMMA does not participate in the polymerization but induces phase separation in the course of the reaction. An experimental study based on real-time static light scattering measurements with the aim of monitoring the phase behavior during the isothermal copolymerization is firstly presented. Then, an original and innovative contribution is made by modeling the evolution of the unstable region of the phase diagram as a function of conversion and by predicting phase separation in spinodal condition. The analysis is performed using an expression for the free energy of a reactive network-forming mixture based on the Flory–Rehner lattice model for swollen gels. The accuracy of the proposed model is verified by the good agreement found between its predictions and the experimental results.

Development of an electrochemical biosensor for the detection of an ADP-ribosylating toxin, exo A from Pseudomonas aeruginosa

A free radical copolymerization of Styrene (Sty) and acrylic acid N-hydroxysuccinimide ester (NAS) has been done in a range of 10:90 to 90:10 (Sty:NAS) molar ratios. The FT-IR spectra for all seven copolymers showed the absorption peaks for the carbonyl signals of the ester and the amide in NAS (1773 cm−1 and 1727 cm−1 respectively), the styrene aromatic signal (1494 cm−1) and the disappearance of the absorption peak for the vinyl group in both monomers (1629 cm−1). HPLC-UV results showed an increment in the average molecular weight with an increase in the molar ratio of the styrene monomer, from 1528.51 g/mol for 10:90 Sty:NAS to 7141.67 g/mol for 90:10 Sty:NAS. These copolymers will be used to generate films on carbon surfaces to anchor a β-NAD+ electroactive analog. Also, a Ferrocene-labeled NAAD (Fc-NAAD) was prepared by attaching Ferrocene Succinimide (Fc-NHS) to the primary amine in the adenine moiety of the cofactor. Osteryoung Squatre Wave Voltammetry (OSWV) of the new Fc-NAAD showed an anodic peak in 320 mV and the cyclic voltammetry (CV) showed chemical reversibility and electrochemical quasi-reversibility.

Reactivity Ratios of the Copolymerization Styrene/ Methyl Methacrylate Using FT-IR Spectroscopy with Comparing to Mathematically Method

Free Radical Copolymerization of Styrene/ Methyl Methacrylate were prepared chemically under Nitrogen ,which was investigated, in the present of Benzoyl Peroxide as Initiator at concentration of 2 × 10-3 molar at 70 °C, which was carried out in Benzene as solvent to a certain low conversion . FT-IR spectra were used for determining of the monomer reactivity ratios ,which was obtained by employing the conventional linearization method of Fineman-Ross (F-R) and Kelen-Tüdos (K- T). The experimental results showed the average value for the Styrene r1 / Methyl Methacrylate r2 system, Sty r1 = 0.45 , MMA r2 = 0.38 in the (F–R) Method and r1 = 0.49 , r2 = 0.35 in the (K–T) Method, The Results of this indicated show the random distribution of monomers in the copolymer.Likewise The monomer reactivity ratios were evaluated Mathematically in comparison in the (F–R) Method with the data STY r1 = 0.61 , MMA r2 = 0.47 , and r1 = 0.45 , r2 =0.38 in the (K–T) Method. And were used the values r1 ,r2 for STY / MMA Copolymers in computing integral curves for the instantaneous Copolymer composition throughout the whole range of conversion.

Reactivity Ratios of the Copolymerization Styrene/ Methyl Methacrylate Using FT-IR Spectroscopy with Comparing to Mathematically Method

Free Radical Copolymerization of Styrene/ Methyl Methacrylate were prepared chemically under Nitrogen ,which was investigated, in the present of Benzoyl Peroxide as Initiator at concentration of 2 × 10-3 molar at 70 °C, which was carried out in Benzene as solvent to a certain low conversion . FT-IR spectra were used for determining of the monomer reactivity ratios ,which was obtained by employing the conventional linearization method of Fineman-Ross (F-R) and Kelen-Tüdos (K- T). The experimental results showed the average value for the Styrene r1 / Methyl Methacrylate r2 system, Sty r1 = 0.45 , MMA r2 = 0.38 in the (F–R) Method and r1 = 0.49 , r2 = 0.35 in the (K–T) Method, The Results of this indicated show the random distribution of monomers in the copolymer.Likewise The monomer reactivity ratios were evaluated Mathematically in comparison in the (F–R) Method with the data STY r1 = 0.61 , MMA r2 = 0.47 , and r1 = 0.45 , r2 =0.38 in the (K–T) Method. And were used the values r1 ,r2 for STY / MMA Copolymers in computing integral curves for the instantaneous Copolymer composition throughout the whole range of conversion.

Synthesis of poly(styrene-co-isopropenyl acetate) -g-polyisobutylene graft copolymers via combination of radical polymerization with cationic polymerization

Random copolymers of poly(styrene-co-isopropenyl acetate) (SIPA) with an average number of 9 initiating sites per chain were synthesized by free radical copolymerization of styrene with a small amount of isopropenyl acetate using 2,2′-azo-bis-(isobutyronitrile) as an initiator at 70 °C. SIPA copolymer could be further used as macroinitiator for the grafting cationic polymerization of isobutylene (IB) from SIPA chain in CH2Cl2 at −40 °C to produce graft copolymers of SIPA-g-PIB. The effect of SIPA concentration ([SIPA]), TiCl4 concentration ([TiCl4]) and IB concentration ([IB]) on initiation efficiency of macroinitiator, grafting efficiency of initiating sites, average length of PIB branches of the resulting graft copolymers were investigated. It can be found that almost all of the initiating sites of IPAc units on SIPA chains were active for the cationic polymerization of IB and both initiation efficiency and grafting efficiency were close to 100% at sufficient molar ratio of TiCl4/IPAc. This synthetic route presents quantitative grafting efficiency and possibility to control length of PIB branches. The graft copolymers of SIPA-g-PIB with average 9-branched PIB chains having terminal functional tert-chlorine groups could be successfully obtained. The average molecular weight of PIB branches in SIPA-g-PIB graft copolymers could be mediated from 3900 to 47,300 g mol−1 by changing the ratios of macroinitiator to monomer and concentration of TiCl4.

Competition between Oxidation and Coordination in Cross-Linking of Polystyrene Copolymer Containing Catechol Groups

In gelation chemistry, catechol groups are used as cross-linking points. Both oxidation and coordination effects of catechol were investigated for their unique features in chemistry by spectroscopic measurements. Polystyrene copolymers containing catechol groups were synthesized by free radical copolymerization of styrene and N-2-(3',4'-ditriethylsilyloxyphenyl)ethyl methacrylamide, and the successive deprotection reaction was catalyzed by tetra-n-butylammonium fluoride. The copolymer containing catechol units afforded a dual cross-linking system based on completely different coordination and oxidation chemistries, and the competing cross-linking mechanisms are discussed. These findings are useful and important for paving the way for designing a novel bioinspired artificial adhesive surface coating and curing system.

Self-assembly of polystyrene with pendant hydrophilic gold nanoparticles: the influence of the hydrophilicity of the hybrid polymers

Polystyrene (PS) with pendant hydrophilic gold nanoparticles (AuNPs) were synthesized by free radical copolymerization of styrene and AuNPs monomer at a liquid–liquid interface. The hybrid polymers can self-assemble into ordered structures in aqueous solutions. The hydrophilicity of the hybrid polymers plays a key role in the self-assembly of the polymers. A decrease in the number of hydrophilic AuNPs results in a transition from a micellar structure to a vesicular structure. After grafting of hydrophilic poly(N-vinyl pyrrolidone) chains to the pendant AuNPs, the self-assembly changes from a vesilcular structure to a core–shell-corona structure. The hybrid polymers and PS-coated Fe3O4 nanoparticles can self-assemble into vesicles with PS and PS-coated Fe3O4 nanoparticles in the walls and AuNPs in the coronae, and the size of the vesicles is determined by the number of pendant AuNPs.

Synthesis of thermosensitive gel by living free radical polymerization mediated by an alkoxyamine inimer

Thermosensitive gel is synthesized through controlled/“living” free radical copolymerization of styrene and DVB mediated by an alkoxyamine inimer, 2,2,6,6-tetramethyl-1-(1′-phenylethoxy)-4-(4′-vinylbenzyloxy)-piperidine (V-ET). The inimer plays the role of both incorporating “T-shaped” inter-chain linkages and mediating the polymerization. First order kinetics is observed for crosslinking polymerizations before gel point, indicating a constant concentration of propagating radicals. Monomer conversion at the gel point depends on the feed ratio of DVB to V-ET. Higher amount of V-ET results in later gel point due to smaller molecular weight of the primary chains that depends inversely on the concentration of nitroxide. The resulting gel contains permanent and labile crosslinking points formed by DVB units and alkoxyamine moieties, respectively. Therefore, the gels exhibit gel–sol transition within a narrow temperature range. The gel properties, such as the swelling ratio and gel–sol transition temperature, can be controlled by changing the feed ratio of DVB to V-ET. The microenvironments in different gels, or at different temperatures, are investigated by ESR spectroscopy.

Composition of fullerene-containing styrene-diallyl isophthalate copolymers

The effect of fullerene C60 on the composition of macromolecules in the free-radical copolymerization of styrene with diallyl isophthalate is estimated. It is shown that the maximum amount of C60 is contained in the high-molecular-mass fraction of the products. Constants in the Kuhn-Mark-Houwink equation are determined for the fullerene-containing copolymer synthesized from an equimolar mixture of monomers.

High Temperature Semibatch Free Radical Copolymerization of Styrene and Butyl Acrylate

AbstractSummary: High temperature semibatch free radical solution copolymerizations of n‐butyl acrylate (BA) and styrene (ST) were carried out over a range of copolymer composition. The significant increase in experimental polymer weight‐average molecular weight with time, as well as the shift in the entire polymer molecular weight distribution, is explained by assuming fast β‐scission of BA midchain radicals with an adjacent styrene unit, followed by subsequent addition of the resultant macromonomer to growing radicals. A mechanistic model including backbiting and β‐scission, macronomer incorporation, long‐chain branching, and propagation and termination penultimate effects was constructed in Predici; the model provides a good representation of the experimental data using rate coefficients taken from literature.

Fabrication of Honeycomb-Structured Porous Surfaces Decorated with Glycopolymers

We prepared breath figure patterns on functional surfaces by the surface segregation of a statistical glycopolymer, (styrene-co-2-(D-glucopyranosyl) aminocarbonyloxy ethyl acrylate (S-HEAGl). The synthesis of the statistical glycopolymer is prepared in a straightforward approach by conventional free radical copolymerization of styrene and the unprotected glycomonomer. Blends of this copolymer and high-molecular-weight polystyrene were spin coated from THF solutions, leading to the formation of surfaces with both controlled functionality and topography. AFM studies revealed that both the composition of the blend and the relative humidity play key roles in the size and distribution of the pores at the interface. Thus, the topographical features obtained on the polymer surfaces during film preparation by the breath figure methodology varied from 200 to 700 nm. Moreover, this approach leads to porous films in which the hydrophilic glycomonomer units are oriented toward the pore interface because upon soft annealing in water the holes are partially swelled. The self-organization of the glycopolymer within the pores was additionally confirmed by the reaction of carbohydrate hydroxyl groups with rhodamine isocyanate. Equally, we demonstrate the bioactivity of the anchored glycopolymers by means of the lectin binding test using concanavalin A (Con A).

Reorganizable Chemical Polymer Gels Based on Dynamic Covalent Exchange and Controlled Monomer Insertion

Covalently networked polymer gels were developed with two notable functionalities: de-cross-linking by dynamic covalent exchange based on a radical crossover reaction and insertion of a monomer into the cross-linkers. The network polymer gels were synthesized by free-radical copolymerization of styrene and a bifunctional monomer with an alkoxyamine linker that has two capabilities to exchange with other alkoxyamine derivatives in the radical process and to polymerize styrene in a controlled manner. Three types of network polymers with different cross-linking densities were obtained by changing the ratio of the bifunctional monomer to styrene. The de-cross-linking reaction was carried out by heating the network polymers with excessive alkoxyamine compound in anisole, and it was made clear that the de-cross-linking behavior strongly depended on the cross-linking densities. The insertion of styrene into the alkoxyamine units at the cross-linking points was also performed by heating the network polymers swollen with styrene and anisole, and it was revealed that the mesh sizes grew larger by the insertion of styrene into their skeleton and that the cross-linking density decreased as the reaction proceeded. The variation of the network structures in these reactions was successfully evaluated by small-angle X-ray scattering and dynamic viscoelasticity measurements.

Kinetics of pseudoliving free-radical copolymerization of styrene and methyl methacrylate by the reversible addition fragmentation chain-transfer mechanism

The kinetics of copolymerization of styrene with methyl methacrylate in the presence of tert-butyl dithiobenzoate as a reversible addition fragmentation chain-transfer agent has been studied. Formation of radical intermediates has been investigated. In a wide range of monomer mixture compositions, the kinetic features of pseudoliving radical copolymerization of this monomer pair in the presence of both a low-molecular-mass reversible addition fragmentation chain-transfer (RAFT) agent and a polymer RAFT agent being formed are close to the corresponding features of the homopolymerization of styrene.

Study of the kinetics of styrene copolymerization with divinyl sulfide and the structure of macromolecules

The kinetics of the free-radical copolymerization of styrene with divinyl sulfide in the presence of N,N′-bis(vinyloxyethyl)thiuram disulfide as an iniferter has been studied. The rate of polymerization is shown to decrease with increasing iniferter concentration. The structure of the copolymers isolated in the course of copolymerization has been investigated by electron microscopy and compared with that of the copolymers synthesized using AIBN as an initiator. Evolution in the morphology of the polymer phase during the process, which consists in self-organization of the secondary supramolecular structure into spheroids with diameters of 0.1–10 μm, has been revealed. The stages of the formation of polymer particles of various structures are described by the scheme of morphogenesis.