Radical Polymerization Of Styrene Research Articles

Ionic liquid-mediated synthesis and self-assembly of poly(ethylene glycol)-block-polystyrene copolymer by ATRP method

Poly(ethylene glycol)-block-polystyrene (PEG-b-PS) was synthesized by the atom transfer radical polymerization of styrene using PEG-Br as the macroinitiator in an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). CuBr and 2,2″-bipyridyl were used as the catalyst and ligand, respectively. The structure, composition, and molecular weight of the PEG-b-PS copolymer were characterized by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and gel permeation chromatography. The PEG-b-PS copolymer with a high molecular weight (Mn = 51,000 g mol−1) and relatively low polydispersity index (PDI = 1.35) was formed at 110 °C for 5 h. Self-assembly of this amphiphilic block copolymer in toluene at different concentrations and in dimethylformamide (DMF)/water systems was also examined. Transmission electron microscopy showed that the block copolymer formed different morphologies spontaneously according to the different solvent systems used.

Chain extension of center-functionalized polystyrene via radical–radical coupling: Periodic introduction of complementary hydrogen bonding interaction site on polymer chain

In this work, our purpose was directed to syntheses of unique polystyrene (PSt) periodically carrying complementary hydrogen-bonded interaction sites in the chain. First, a bifunctional (bi-headed) initiator carrying three-point complementary hydrogen bonding sites (Cl–DAD–Cl: D=hydrogen donor; A=hydrogen acceptor) was employed for ruthenium-catalyzed living radical polymerization of styrene. Precise control of the polymerization allowed quantitative introduction of the DAD unit at the center and Cl capping group at the terminals for the resultant PSt chain as well as narrow molecular weight distribution. Generation of concentrated radical species from the C–Cl bonds at the both terminals in the absence of monomer induced radical–radical coupling reaction between the styryl radical species for “chain extension”. Since molecular weight distribution of the precursor was enough narrow (Mw/Mn<1.10) and the DAD unit was quantitatively incorporated at the central position, the resultant polymer chains carried the complementary interaction site at regular interval corresponding to the chain length (molecular weight) of the precursor. The position-controlled polystyrene chain interacted with poly(methyl methacrylate) having the complementary interaction unit (ADA) at the center to give supramolecular graft copolymer.

Facile and Versatile Platform Approach for the Synthesis of Submicrometer-Sized Hybrid Particles with Programmable Size, Composition, and Architecture Comprising Organosiloxanes and/or Organosilsesquioxanes

We present a facile and versatile platform approach for the synthesis of submicrometer-sized hybrid particles based on an oil-in-water emulsion. These particles comprise organosiloxanes and/or organosilsesquioxanes formed via hydrolysis and polycondensation of alkyl- or aryltrimethoxysilane, and polystyrene or poly(methyl methacrylate) formed through radical polymerization of styrene and methyl methacrylate, respectively. In this synthesis, the alkyl- or aryltrimethoxysilane fulfills three different roles: (i) it is part of the oil phase, (ii) serves as monomer for the formation of the organosiloxane network, and (iii) forms a surface active species that stabilizes the emulsion. Size, composition and architecture of the resulting hybrid particles are programmable in this synthetic approach, as demonstrated for the combination phenyltrimethoxysilane/styrene. The versatility of the approach is demonstrated by preparing hybrid particles based on following precursor/monomer combinations: phenyltrimethoxysilane/methyl methacrylate, methyltrimethoxysilane/styrene, (3-acryloxypropyl)-trimethoxysilane/styrene and (3-mercaptopropyl)trimethoxysilane/styrene. Latter combination yields hybrid spheres with thiol groups suited for further functionalization.

Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798gmol−1. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric analysis shows that thermal stability of the nanocomposites increases by adding nanoparticles content. Decrease of glass transition temperature is also demonstrated by the addition of 3wt% of silica nanoparticles according to the differential scanning calorimetry results.

Corrosion behavior of aluminum/silica/polystyrene nanostructured hybrid flakes

The corrosion protection of aluminum flake pigments has been extended by means of an encapsulating inorganic/organic silica/polystyrene hybrid nanolayer. A silica nanolayer encapsulated the surface of aluminum flakes (Al) by hydrolysis and polycondensation of tetraethylorthosilicate via sol–gel process to yield Al/Si flakes. Then, 3-methacryloxypropyltrimethoxysilane (MPS) was used as surface modifier which has polymerizable groups to participate in polymerization reaction (Al/Si/MPS). A polystyrene (PS) coating layer was applied on Al/Si/MPS flakes by free radical polymerization of styrene initiating with Azobisisobutyronitrile at 60 °C and subsequent washing of free chains with solvent yielded Al/Si/PS flakes. Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy showed that silica and PS nanolayers were formed on the aluminum flakes. The attached PS chains on the surface were detached by hydrofluoric acid aqueous solution and analyzed by gel permeation chromatography (GPC). Also, a transmission electron microscopy image showed clearly that the encapsulating layers are in the scale of nano. Good results were obtained in terms of corrosion protection in acidic and alkaline solutions, indicating that the silica/polymer hybrid nanolayer coating acts as an efficient protective film. After encapsulating the flakes, the evolved hydrogen volume was dropped and hybrid nanolayer resulted in no evolved hydrogen volume.

Atom transfer radical polymerization (ATRP) and organometallic mediated radical polymerization (OMRP) of styrene mediated by diaminobis(phenolato)iron(II) complexes: a DFT study.

This study has addressed the radical polymerization of styrene mediated by the diaminobis(phenolate) complexes [Fe(O-2,4-Y2C6H2-5-CH2)2NCH2CH2NMe2], abbreviated as [Fe(II)]. The system is known to be well controlled when Y = Cl but not when Y = alkyl. The control was proposed to occur by a dual ATRP+OMRP mechanism. We have used DFT calculations to address the Y = Cl and Y = CH3 systems. The growing radical chain, ATRP dormant chain, and OMRP dormant chain were simplified to PhCH(CH3)(•), PhCH(CH3)-Cl, and [PhCH(CH3)-Fe(III)]. The idealized ATRP activation/deactivation equilibrium involves [Fe(III)-Cl] (I(Y)) and PhCH(CH3)(•) on the active side and [Fe(II)] (II(Y)) and PhCH(CH3)-Cl on the dormant side, whereas the OMRP activation/deactivation relates [Fe(II)] and PhCH(CH3)(•) with [PhCH(CH3)-Fe(III)] (III(Y)). A benchmarking of various functionals against the known spin properties of alkylporphyriniron(III) shows B3PW91* to be a suitable functional. For the purpose of bond dissociation energy calculations, a dispersion correction was made (B3PW91*-D3). For both Y systems, the ground state is a spin sextet for I, a spin quintet for II, and a spin quartet for III. The calculations show a greater energy cost for the ATRP activation process involving Cl atom addition to II(Cl) to yield I(Cl) (7.2 kcal/mol) relative to the process transforming II(Me) to I(Me) (2.1 kcal/mol). On the other hand, the alkyl addition transforming II to III provides slightly greater stabilization for II(Cl) (27.1 kcal/mol) than for II(Me) (26.1 kcal/mol). As a result, both ATRP and OMRP trapping processes provide greater stabilization for the Y = Cl system, in agreement with the observed better control. The charge analysis attributes these minor but determining energy differences to the inductive electron withdrawing effect of the phenolato Cl substituents. The ATRP and OMRP activation/deactivation pathways have been analyzed in relation to the spin state change; they show in each case the absence of an activation barrier, and both processes corresponding to spin allowed single-state pathways occurring on the quartet (OMRP) and quintet (ATRP) potential energy surfaces. Molecular volume calculations suggest that the balance between ATRP and OMRP may shift in favor of the latter at higher pressures.

Palygorskite/polystyrene nanocomposites via facile in-situ bulk polymerization: Gelation and thermal properties

Novel palygorskite/polystyrene (PLG/PS) nanocomposites were synthesized via the facile in-situ bulk radical polymerization of styrene in the presence of the organo-palygorskite (Org-PLG) nanorods, which was prepared by the modification of the acid-activated palygorskite (A-PLG) nanorods with the functional silane (γ-methacryloxypropyl trimethoxy silane (MPS)). The micro-gels with the Org-PLG nanorods as crosslinker were produced in the PLG/PS nanocomposites regardless of the polymerizing conditions, such as the feeding ratios of the Org-PLG, initiator and N2 atmosphere. Based on the gelation and thermal properties of the PLG/PS nanocomposites, the optimal preparation condition via the in-situ bulk polymerization was achieved and the crosslinking mechanism to the micro-gels was also depicted. This understanding should lead to a better design of clay mineral modifications for use in polymer nanocomposites.

Iron-mediated AGET ATRP of styrene and methyl methacrylate using ascorbic acid sodium salt as reducing agent

Atom transfer radical polymerization of styrene (St) and methyl methacrylate (MMA) in bulk and in different solvents using activators generated by electron transfer (AGET ATRP) were investigated in the presence of a limited amount of air using FeCl3·6H2O as the catalyst, ascorbic acid sodium salt (AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide (TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.

Cobalt complex bearing β‐ketoamine ligand: syntheses, structure, catalytic behavior for styrene and methyl methacrylate polymerization

Cobalt complex based on β‐ketoamine ligand [(Z)‐4‐((2,5‐dimethylphenylamino) (phenyl)methylene)‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one] was successfully synthesized. The produced catalyst showed satisfactory activities in the cobalt‐mediated radical polymerization of styrene and methyl methacrylate with the common initiator of AIBN. The resulting polymerizations have the characteristics of living radical polymerization and displayed a nearly linear correlation between the number‐average molecular weight and monomer conversion. Low polydispersity was obtained for all polymerizations, and the polydispersity index decreased with the increase of conversion. These improvements facilitate the implementation of styrene and methacrylate cobalt‐mediated radical polymerization, and open the door to the scale‐up of the process. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Computer simulation of the reversible addition-fragmentation chain transfer radical polymerization of styrene: Relationship between molecular-weight characteristics of the polymer and process conditions

Computer simulation of the reversible addition-fragmentation chain transfer radical polymerization of styrene: Relationship between molecular-weight characteristics of the polymer and process conditions

Edge‐functionalized graphene nanoplatelets with polystyrene by atom transfer radical polymerization: grafting through carboxyl groups

AbstractThe surface modifier 3‐((4‐hydroxybutoxy)dimethylsilyl)propyl methacrylate (CD), which contains a double bond and a hydroxyl group, was synthesized through a coupling reaction of 1,4‐butanediol and (3‐methacryloxypropyl)dimethylchlorosilane. Subsequently, graphene oxide (GO) was functionalized with different amounts of CD from its edge carboxyl groups. Then, grafting through atom transfer radical polymerization of styrene in the presence of various amounts of the edge‐functionalized GO was carried out to evaluate the effect of graphene loading along with graft density. A peak at 3.8 ppm in the 1H NMR spectrum of CD associated with the methylene adjacent to the Si–O group indicated a successful coupling reaction. Attachment of CD on the edges of GO was evaluated using X‐ray photoelectron and Fourier transform infrared spectroscopies. Expansion of GO interlayer spacing by functionalization was evaluated using X‐ray diffraction. The ordered and disordered crystal structure of carbon was studied using Raman spectroscopy. The close ID/IG values for GO and various kinds of functionalized graphenes show the preserved graphitic crystallite size. Relaxation behaviour of polystyrene chains in the presence of graphene nanoplatelets and also the effect of graft content on chain confinement were studied using differential scanning calorimetry. High‐graft‐density nanocomposites show higher glass transition temperatures. Morphology of graphene nanoplatelets was studied using scanning electron and transmission electron microscopies. The flat and smooth morphology of graphene nanoplatelets is disturbed and also the transparency of the nanoplatelets decreases during the oxidation and functionalization processes. © 2014 Society of Chemical Industry

Well‐Defined Iron Complexes as Efficient Catalysts for “Green” Atom‐Transfer Radical Polymerization of Styrene, Methyl Methacrylate, and Butyl Acrylate with Low Catalyst Loadings and Catalyst Recycling

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(μ-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4 b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4 b (59 ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4 b (117 ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28 ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined.

Monte Carlo simulation of free radical polymerization of styrene in a spinning disc reactor

We report on modeling of free-radical polymerization of styrene in a stirred tank reactor–spinning disc reactor (STR–SDR) arrangement using Kinetic Monte Carlo (KMC) simulation algorithm. The prepolymer from batch reactor was transferred to SDR and simulation results were validated comparing conversion and molecular weight of the generated molecules in the batch reactor and SDR with corresponding values from experimental data. The developed model was also applied to simulate SDR under a range of different operating conditions to accurately predict the resulting polymer properties. In this way, different prepolymer conversions were theoretically adapted to probe the evolution in chain microstructure until polymerization terminated on the rotating disc. The developed computer code based on KMC approach enables precise monitoring of molecular-level events in the reactor like variations in molar concentration of macroradicals and molecular weight distribution with time, and provides a greater insight into the STR–SDR cascade polymerization of styrene monomer.

Synthesis and Catalytic Reactions of Nanoparticles formed by Electrospray Ionization of Coinage Metals

AbstractNoble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped‐nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p‐nitrophenol by NaBH4. Efficient catalysis was also observed by simply directing the spray of solvated Au+ onto the surface of an aqueous p‐nitrophenol/NaBH4 mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, CuI bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene.

Synthesis and Catalytic Reactions of Nanoparticles formed by Electrospray Ionization of Coinage Metals

Noble metals can be ionized by electrochemical corrosion and transported by electrospray ionization. Mass spectrometry (MS) showed solvated metal ions as the main ionic constituent of the sprayed droplets. Collection of the electrospray plume on a surface yielded noble metal nanoparticles (NPs) under ambient conditions. The NPs were characterized by several techniques. Under typical conditions, capped-nanoparticle sizes averaged 2.2 nm for gold and 6.5 nm for silver. The gold nanoparticles showed high catalytic activity in the reduction of p-nitrophenol by NaBH4 . Efficient catalysis was also observed by simply directing the spray of solvated Au(+) onto the surface of an aqueous p-nitrophenol/NaBH4 mixture. Organometallic ions were generated by spiking ligands into the spray solvent: for example, Cu(I) bipyridine cations dominated the spray during Cu electrocorrosion in acetonitrile containing bipyridine. This organometallic reagent was shown to be effective in the radical polymerization of styrene.

One‐Pot Synthesis of Poly(linoleic acid)‐g‐Poly(styrene)‐g‐Poly(ε‐caprolactone) Graft Copolymers

AbstractOne‐pot synthesis of graft copolymers by ring‐opening polymerization and free radical polymerization using polymeric linoleic acid peroxide (PLina) is reported. Graft copolymers having structures of poly(linoleic acid)‐g‐polystyrene‐g‐poly(ε‐caprolactone) were synthesized from PLina, possessing peroxide groups on the main chain by the combination of free radical polymerization of styrene and ring‐opening polymerization of ε‐caprolactone in one‐step. Principal parameters, such as monomer concentration, initiator concentration, and polymerization time, which effect the one‐pot polymerization reactions were evaluated. The obtained graft copolymers were characterized by 1H‐NMR and DOSY‐NMR spectroscopy, gel permeation chromatography, thermal gravimetric analysis and differential scanning calorimetry techniques.

Well-defined second-order nonlinear optical polymers by controlled radical polymerization, via multifunctional macromolecular chain transfer agent: Design, synthesis, and characterizations

To address the issue of the aggregation in second-order nonlinear optical (NLO) polymers we developed an approach based on the synthesis of a multifunctional macromolecular chain transfer agent. The controlled monomer insertion polymerization into the main chain by a ‘reversible addition-fragmentation chain transfer’ (RAFT) mechanism allows the spatial arrangement of the NLO chromophores along the polymeric chain in order to obtain sequence-ordered polymers. In a first step, a novel trithiocarbonate based macroinitiator containing the disperse red 19 (DR19) units in the main chain was synthesized by polycondensation; in a second step, this polymeric precursor was applied to the synthesis of a sequentially ordered polymer by controlled insertion radical polymerization of styrene. Size exclusion chromatography (SEC), nuclear magnetic resonance (NMR) data revealed that, (i) for the first time, polystyrenes (PS) bearing DR19 dyes covalently bounded were obtained, and (ii) both the insertion reaction and the length of the polystyrene segments were accurately controlled. Whatever the incorporated dye amount, all the copolymers were soluble in common solvents. Second-order optical nonlinearity in corona-poled thin films was evaluated, and second harmonic coefficients up to 80 pm/V were determined for loading ratio lower than 10 wt-% (DR19/PS). This approach opens up opportunities for the incorporation of more efficient chromophores even in apolar matrices.

A polyester–polystyrene hybrid connected by dynamic covalent bonds prepared via radical polymerization of styrene in a “RAFT gel”

We cross-linked the polyester chains with 1,1-thiocarbonyldiimidazole to form a reversible addition–fragmentation chain-transfer (RAFT) gel, in which the trithiocarbonate moiety acted as a cross-linker. The “RAFT gel” was then swollen in vinyl monomers and styrene was radically polymerized within the gel, in which the polyester and polystyrene segments were miscible at the segment level.

Critically evaluated rate parameters for chain-length-dependent termination in radical polymerization of styrene and n-alkyl methacrylates

Critically evaluated rate parameters for chain-length-dependent termination in radical polymerization of styrene and n-alkyl methacrylates

Synthesis of mixed poly(ε-caprolactone)/polystyrene brushes from Y-initiator-functionalized silica particles by surface-initiated ring-opening polymerization and nitroxide-mediated radical polymerization

This article reports the synthesis of mixed brushes by ring-opening polymerization of ε-caprolactone and nitroxide-mediated radical polymerization of styrene from Y-initiator-functionalized silica particles.