A novel process for synthesizing polystyrene and polyarylate block copolymers utilizing telechelic polystyrene

A novel process for synthesizing polystyrene (PS) and polyarylate (PAr) block copolymers utilizing telechelic polystyrene was proposed. This process was comprised of three steps. In the first step, carboxyl-terminated telechelic polystyrene (COOH PS COOH) was prepared by free radical polymerization with 4,4′-azobis(cyanovalelic acid) (ACVA). In the second step, COOH PS COOH was reacted with bisphenol-A by the use of triphenylphosphine, hexachloroethane, and triethylamine to convert carboxyl groups into phenol groups (OH PS OH). In the third step, to produce the PS PAr block copolymer, OH PS OH was added to a polyarylate synthesizing system where bisphenol-A and the mixture of tere/isophthaloyl dichloride (1 : 1 mole ratio) were polymerized by solution polycondensation. PS PAr block copolymers were successively obtained with relatively high PS copolymerization ratio. The ratio was over 70%, while there was a wide variety in molecular composition and molecular weight. Furthermore, by this process PS PAr block copolymers can be obtained from step 1 through step 3 consecutively without isolating the intermediates. This method has potential for industrial applications. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2839–2847, 1998     

Compatibilizing effect of polyarylate-polystyrene block copolymer in polyarylate/polystyrene blends

The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc.     

Synthesis of carboxy‐telechelic oligostyrene by dead‐end polymerization: Evaluation of primary radical termination by kinetic study and kinetic simulation model

Styrene was polymerized with azobiscyanovaleric acid (ACVA) to obtain carboxy‐telechelic polystyrene. Our aim was to synthesize an oligostyrene with a molecular weight of about 2000 g/mol. Thus, styrene was polymerized at 90 °C, where t_1/2ACVA is very short, and at very high initiator concentrations. In these conditions a new termination reaction appeared, known as the primary radical termination (PRT). At first, PRT was observed by a deviation from the simple kinetic law. Then, the constant of PRT was determined by several kinetic models to be more important than the constant of bimolecular termination. Finally, the PREDICI simulation program was used to confirm the predominance of PRT. This simulation program allowed the determination of the constant of primary radical deactivation k_rr and the influence of this reaction on the conversion rate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2740–2750, 2001     

Polyarylate–polystyrene block copolymer from macro-azoinitiator: Synthesis and its thermal properties

A macro-azoinitiator containing polyarylate segment and azo group was prepared by the solution polycondensation of azobiscyanopentanoyl chloride and hydroxy-terminated polyarylates having viscosity-average molecular weights of 6200, 8100, and 12 400. These macro-azoinitiators were used in the radical polymerization of styrene to synthesize polyarylate-polystyrene block copolymers. Thermal properties measured by the differential scanning calorimetry indicated the phase separated morphology of the block copolymers except at low molecular weight of the block constituents. © 1993 John Wiley & Sons, Inc.     

A versatile approach for the preparation of end‐functional polymers and block copolymers by stable radical exchange reactions

A versatile strategy for the preparation of end‐functional polymers and block copolymers by radical exchange reactions is described. For this purpose, first polystyrene with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl end group (PS‐TEMPO) is prepared by nitroxide‐mediated radical polymerization (NMRP). In the subsequent step, these polymers are heated to 130 °C in the presence of independently prepared TEMPO derivatives bearing hydroxyl, azide and carboxylic acid functionalities, and polymers such as poly(ethylene glycol) (TEMPO‐PEG) and poly(ε‐caprolactone) (TEMPO‐PCL). Due to the simultaneous radical generation and reversible termination of the polymer radical, TEMPO moiety on polystyrene is replaced to form the corresponding end‐functional polymers and block copolymers. The intermediates and final polymers are characterized by ¹H NMR, UV, IR, and GPC measurements. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2387–2395     

Hyperbranched block copolymer from AB2 macromonomer: Synthesis and its reaction‐induced microphase separation in epoxy thermosets

In this contribution, we reported the synthesis of a hyperbranched block copolymer composed of poly(ε‐caprolactone) (PCL) and polystyrene (PS) subchains. Toward this end, we first synthesized an α‐alkynyl‐ and ω,ω′‐diazido‐terminated PCL‐b‐(PS)₂ macromonomer via the combination of ring‐opening polymerization and atom transfer radical polymerization. By the use of this AB₂ macromonomer, the hyperbranched block copolymer (h‐[PCL‐b‐(PS)₂]) was synthesized via a copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition (i.e., click reaction) polymerization. The hyperbranched block copolymer was characterized by means of ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography. Both differential scanning calorimetry and atomic force microscopy showed that the hyperbranched block copolymer was microphase‐separated in bulk. While this hyperbranched block copolymer was incorporated into epoxy, the nanostructured thermosets were successfully obtained; the formation of the nanophases in epoxy followed reaction‐induced microphase separation mechanism as evidenced by atomic force microscopy, small angle X‐ray scattering, and dynamic mechanical thermal analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 368–380     

The 25th anniversary of catalytic chain transfer

The transfer of hydrogen from a free radical to an olefin is catalyzed by some cobalt chelates. This reaction, when used in free-radical polymerization, can be called catalytic chain transfer (CCT) to a monomer. It allows the manufacture of oligomers that have defined molecular weights and are useful for a variety of applications. Because all the oligomers are getting terminal double bonds, they can behave as macromers. These macromers give rise to the formation of diblock and graft copolymers, telechelic polymers that have the same or different functional groups depending on the conditions and origins of the comonomers. The catalyst structure–property relation is discussed. Redox properties affect the CCT and provide additional leverage in controlling polymerization processes. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1753–1766, 2000     

Modeling the molecular weight distribution of block copolymer formation in a reversible addition–fragmentation chain transfer mediated living radical polymerization

Block copolymers have become an integral part of the preparation of complex architectures through self‐assembly. The use of reversible addition–fragmentation chain transfer (RAFT) allows blocks ranging from functional to nonfunctional polymers to be made with predictable molecular weight distributions. This article models block formation by varying many of the kinetic parameters. The simulations provide insight into the overall polydispersities (PDIs) that will be obtained when the chain‐transfer constants in the main equilibrium steps are varied from 100 to 0.5. When the first dormant block [polymer–S? C(Z)?S] has a PDI of 1 and the second propagating radical has a low reactivity to the RAFT moiety, the overall PDI will be greater than 1 and dependent on the weight fraction of each block. When the first block has a PDI of 2 and the second propagating radical has a low reactivity to the RAFT moiety, the PDI will decrease to around 1.5 because of random coupling of two broad distributions. It is also shown how we can in principle use only one RAFT agent to obtain block copolymers with any desired molecular weight distribution. We can accomplish this by maintaining the monomer concentration at a constant level in the reactor over the course of the reaction. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5643–5651, 2005     

Syntheses and characterizations of polypropene,polystyrene and their block copolymers with titanocene catalysts

Pentamethylcyclopentadienyltitanium tribenzyloxide, Cp^*Ti(OBz)₃, was used as the catalyst precursor for polymerizations of propene and styrene. The titanocene catalyst affords atactic polypropene and syndiotactic polystyrene with high activities in the presence of methylalumimoxane (MAO). Block copolymerization of propene and styrene was carried out in the presence of Cp^*Ti(OBz)₃/MAO catalyst system by the means of external addition of triisobutylaluminum (TIBA) and sequential monomer feed. The copolymerization product is mainly a mixture of atactic polypropene(aPP) and syndiotactic polystyrene(sPS) homopolymers and aPP-b-sPS block copolymers, which can be separated into fractions with successive extraction with boiling methylethyl ketone(MEK), heptane, tetrahydrofuran(THF), and chloroform. Studies on thermal properties showed that rubbery phases and crystalline regions both appear in the block copolymer at the room temperature and that aPP-b-sPS block copolymer has better toughness than sPS.     

Effect of thermal history on the ionic conductivity of block copolymer electrolytes

We have studied the effect of thermal history on ionic conductivity of block copolymer electrolytes. Previous work on block copolymer electrolytes composed of polystyrene‐b‐poly(ethylene oxide) (SEO) and lithium bis(trifluoromethanesulfone) imide (LiTFSI) salt was restricted to lamellar morphologies. This study addresses both cylindrical and lamellar morphologies. The conductivity of low molecular weight samples decreases after they are annealed. In contrast, the conductivity of high molecular weight samples is generally unaffected by annealing. These results are explained in the context of connectivity and composition of the conducting phase. © 2013 Wiley Periodicals, Inc. J. Polym. Sci. Part B: Polym. Phys. 2013 , 51, 927–934     

Synthesis of transparent block copolymers consisting of poly(diisopropyl fumarate) and poly(2-ethylhexyl acrylate) segments by reversible addition-fragmentation chain transfer polymerization using trithiocarbonates as the chain transfer agents

The reversible addition-fragmentation chain transfer polymerization of diisopropyl fumarate (DiPF) was carried out using ethyl 2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate (T1) and 1,1′-(1,2-ethanediyl) bis[2-[[(dodecylthio)thioxymethyl]thio]-2-methylpropionate] (T2) as the monofunctional and difunctional chain transfer agents (CTAs) to synthesize poly(diisopropyl fumarate) (PDiPF) with a rigid chain conformation. The obtained PDiPF had a well-controlled molecular weight, molecular weight distribution, and structure of the chain ends. Size exclusion chromatography and NMR measurements revealed an excellent introduction efficiency (84–98%) of the terminal trithiocarbonate group into the polymer chain end. They were available as the monofunctional and difunctional macro-CTAs to synthesize the AB and ABA block copolymers, respectively. While the well-controlled block copolymers were solely obtained by the polymerization of 2-ethylhexyl acrylate as the second monomer in the presence of PDiPF as the macro-CTA, the block copolymerization of DiPF using poly(2-ethylhexyl acrylate) as the macro-CTA failed. The trithiocarbonate group at the chain end was completely removed by the reaction with n-butylamine and it was valid for the improvement of the coloration and other optical properties of the transparent polymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2584–2594     

Synthesis of i‐PP‐based functional block copolymer by a facile combination of styryl‐capped i‐PP and ATRP

This article demonstrates a facile and efficient method to combine olefin coordination polymerization with atom transfer radical polymerization (ATRP) for the synthesis of isotactic polypropylene (i‐PP)‐based functional diblock copolymers. The chemistry involves a styryl‐capped i‐PP precursor prepared through the controlled consecutive chain transfer reaction, first to 1,2‐bis(4‐vinylphenyl)ethane and then to hydrogen in propylene polymerization mediated by an isospecific metallocene catalyst. The i‐PP precursor can be quantitatively transformed into i‐PP terminated with a 1‐chloroethylbezene group (i‐PP‐t‐Cl) by a straightforward hydrochlorination process using hydrogen chloride. With the resultant i‐PP‐t‐Cl as a macroinitiator of ATRP, methyl methacrylate (MMA) polymerization was exemplified in the presence of CuBr/pentamethyldiethylenetriamine, preparing i‐PP‐b‐PMMA copolymers of different PMMA contents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Sequential photodecomposition of bisacylgermane type photoinitiator: Synthesis of block copolymers by combination of free radical promoted cationic and free radical polymerization mechanisms

A block copolymer of cyclohexene oxide (CHO) and styrene (St) was prepared by using bifunctional visible light photoinitiator dibenzoyldiethylgermane (DBDEG) via a two‐step procedure. The bifunctionality of the photoinitiator pertains to the sequential photodecomposition of DBDEG through acyl germane bonds. In the first step, photoinitiated free radical promoted cationic polymerization of CHO using DBDEG in the presence of diphenyliodonium hexafluorophosphate (Ph₂I⁺PF) was carried out to yield polymers with photoactive monobenzoyl germane end groups. These poly(cyclohexene oxide) (PCHO) prepolymers were used to induce photoinitiated free radical polymerization of styrene (St) resulting in the formation of poly(cyclohexene oxide‐block‐styrene) (P(CHO‐b‐St)). Successful blocking has been confirmed by a strong change in the molecular weight of the prepolymer and the block copolymer as well as NMR, IR, and DSC spectral measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4793–4799, 2009     

Synthesis of miktoarm star and miktoarm star block copolymers via a combination of atom transfer radical polymerization and stable free‐radical polymerization

A trifunctional initiator, 2‐phenyl‐2‐[(2,2,6,6‐tetramethyl)‐1‐piperidinyloxy] ethyl 2,2‐bis[methyl(2‐bromopropionato)] propionate, was synthesized and used for the synthesis of miktoarm star AB₂ and miktoarm star block AB₂C₂ copolymers via a combination of stable free‐radical polymerization (SFRP) and atom transfer radical polymerization (ATRP) in a two‐step or three‐step reaction sequence, respectively. In the first step, a polystyrene (PSt) macroinitiator with dual ω‐bromo functionality was obtained by SFRP of styrene (St) in bulk at 125 °C. Next, this PSt precursor was used as a macroinitiator for ATRP of tert‐butyl acrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80 °C, affording miktoarm star (PSt)(PtBA)₂ [where PtBA is poly(tert‐butyl acrylate)]. In the third step, the obtained St(tBA)₂ macroinitiator with two terminal bromine groups was further polymerized with methyl methacrylate by ATRP, and this resulted in (PSt)(PtBA)₂(PMMA)₂‐type miktoarm star block copolymer [where PMMA is poly(methyl methacrylate)] with a controlled molecular weight and a moderate polydispersity (weight‐average molecular weight/number‐average molecular weight < 1.38). All polymers were characterized by gel permeation chromatography and ¹H NMR. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2542–2548, 2003     

Nonaqueous dispersion polymerization of styrene in methanol with the ionomer block copolymer poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer

The nonaqueous dispersion polymerization of styrene in methanol with poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)]‐b‐polyisobutene as a stabilizer was investigated. There was no observable inducing period or autoacceleration in the polymerization process. The conversion increased almost linearly with the polymerization time as high as 80%. The average sizes of the obtained polystyrene particles increased, and the size distributions of the polystyrene particles tended to become narrower, with increasing conversion. The mechanism of the dispersion polymerization in the presence of polyisobutene‐b‐poly[(4‐methylstyrene)‐co‐(4‐vinyltriethylbenzyl ammonium bromide)] was nucleation/growth. When the stabilizer/monomer ratio (w/w) was greater than 2.0%, the polystyrene dispersion was stable, and there was no observable polymer particle coagulation taking place during the whole polymerization process. The average diameter of the polymer particles can be mediated through changes in the polymerization conversion, monomer, and stabilizer. Nearly monodispersed polystyrene particles with average diameters of approximately 0.45–2.21 μm were obtained under optimal conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2678–2685, 2004     

Poly[(R)‐3‐hydroxybutyrate)]/poly(styrene) blends compatibilized with the relevant block copolymer

A novel triblock copolymer PS–PHB–PS based on the microbial polyester Poly[(R)‐3‐hydroxybutyrate)] (PHB) and poly(styrene) (PS) was prepared to be used as compatibilizer for the corresponding PHB/PS blends. It was prepared in a three‐step procedure consisting of (i) transesterification reaction between ethylene glycol and a high‐molecular‐weight PHB, (ii) synthesis of bromo‐terminated PHB macroinitiator, and (iii) atom transfer radical polymerization polymerization of styrene initiated by the PHB‐based macroinitiator. Fourier transform infrared, gel permeation chromatography, ¹H‐, and ¹³C‐NMR spectroscopies were used to determine the molecular structure and/or end‐group functionalities at each step of the procedure. Although thermogravimetric analysis showed that the block copolymer underwent a stepwise thermal degradation and had better thermal stability than their respective homopolymers, differential scanning calorimetry displayed that the PHB block in the copolymer could not crystallize, and thus generating a total amorphous structure. Atomic force microscopy images indicated that the block copolymer was phase segregated in a well‐defined morphological structure with nanodomain size of ～40 nm. Contact angle measurements proved that the wettability properties of the block copolymer were in between those of the PHB and PS homopolymers. Blends analyzed for their morphology and thermal properties showed good miscibility and had well‐defined morphological features. Polymer blends exhibited lower crystallinity and decreased stiffness which was proportional to the amount of compatibilizer content in the blends. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of block copolymers of polystyrene and poly (t‐butyl acrylate) of various molecular weights and architectures by atom transfer radical polymerization

Block copolymers of polystyrene and poly(t‐butyl acrylate) were prepared using atom transfer radical polymerization techniques. These polymers were synthesized with a CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system and had predictable molecular weights based on the degree of polymerization, as calculated from the initial ratio of monomer to initiator. The final polydispersities were low (1.10 < M_w /M_n < 1.3) for all the homopolymers and block copolymers. Polymers of various chain architectures were prepared, ranging from linear AB diblocks to three‐armed stars composed of AB diblocks on each arm. The key to controlled synthesis with this catalyst system was the choice of the solvent, temperature, and concentrations of catalyst and deactivator. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2274–2283, 2000     

Synthesis and characterization of double thermo‐responsive block copolymer consisting N‐isopropylacrylamide by atom transfer radical polymerization

In this thesis, we studied the convenient synthesis and characterizations of thermo‐responsive materials with double response. To achieve these, AB‐type diblock copolymers comprising of poly(N‐isopropylacrylamide) (NIPAAm) segment and poly(NIPAAm‐co‐(N‐(hydroxymethyl)acrylamide) (HMAAm)) one were designed. That was synthesized in one‐pot using an atom transfer radical polymerization (ATRP) technique. Poly(NIPAAm‐co‐HMAAm)s synthesized separately showed sensitive thermo‐response and the cloud point was completely tunable by the composition of HMAAm. As expected, the block copolymers exhibited double thermo‐responsive profiles in aqueous solution. The responsive behavior was discussed by precise trace by ¹H NMR and turbidity measurements. From these results, we could confirm almost independent dehydration of each segment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6142–6150, 2008