Synthesis of sub‐micrometer core–shell rubber particles with 1,2‐azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditions

BACKGROUND: Sub‐micrometer core‐shell polybutadiene‐graft‐polystyrene (PB‐g‐PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2‐azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB‐g‐PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core‐shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ‘cluster’ dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge‐like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ‘cluster’ state leads to better impact resistance. The deformation mechanism in impact tests was multi‐crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry     

Synthesis and physicochemical properties of poly[2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline] obtained with various dopants

Highly soluble polyaniline was synthesized from a newly designed aniline derivative, namely 2‐[2‐chloro‐1‐methylbut‐2‐en‐1‐yl]aniline. The corresponding polyanilines, PClPA‐HA, PClPA‐SA, PClPA‐NA and PClPA‐PA, were characterized by means of ¹H NMR, ¹³C NMR, high resolution mass spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and SEM images. The elemental analysis and electrical conductivity of the polymers are also presented. It is shown that the molecular weight of the polymers obtained depends on the method of synthesis. Spectroscopic studies confirmed the emeraldine form of the polyaniline derivatives. In the work, the dependence of the current passing through resistive structures based on thin poly[2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline] films on the relative humidity of air was studied. The results of the studies showed the prospects of using thin polymer films in the design of chemical sensors. © 2020 Society of Chemical Industry     

Synthesis of ultra‐high molecular weight polystyrene with rare earth–magnesium alkyl catalyst system: general features of bulk polymerization

Bulk polymerization of styrene (St) with an in‐situ‐activated Ziegler‐catalyst containing neodymium 2‐ethylhexyl phosphonate [Nd(P₂₀₄)₃], magnesium–aluminum alkyls and hexamethyl phosphoramide (HMPA) was studied. The new rare‐earth catalyst exhibited high activity for polymerization of styrene, and its catalytic efficiency reached 14 730 g PSt/g Nd. The influence of reaction parameters, such as Mg/Nd, Mg/Al, St/Nd molar ratios, temperature, etc, on the catalyst performance was examined in detail. The molecular weight of the resulting polystyrene is ultra‐high (M_W = 40 × 10⁴ ∼ 120 × 10⁴ g mol⁻¹) and the distribution of molecular weight is broad (M_W/M_n = 2.1 ∼ 2.8). The microstructure of the polystyrene was characterized by IR and ¹³C NMR spectroscopies and found to be atactic. © 2001 Society of Chemical Industry     

Removal of nitro aromatic compounds and sulfite acid from distillate of 2,4,6‐trinitrotoluene red water using modified porous polystyrene microspheres

To remove the nitro aromatic compounds (NACs) and SO₃^2? from distillate of 2,4,6‐trinitrotoluene (TNT) red water, the carboxylated and aminated polystyrene (PSt) microspheres were used as adsorbents. GC‐MS and HPLC analysis were used to determine the types and concentrations of NACs before and after adsorption. The carboxylated PSt, which was prepared by modifying PSt with phthlandione (PA), could remove the neutral NACs including 2,6‐dinitrotoluene (2,6‐DNT), 2,4‐dinitrotoluene (2,4‐DNT), 1,3,5‐trinitrobenzene (1,3,5‐TNB), and 2,4,6‐trinitrotoluene (2,4,6‐TNT), with the acid 2,4‐dinitrophenol (2,4‐DNP) and SO₃^2? remained in the distillate. The aminated PSt that was synthesized by activating PSt with chloroacetyl chloride follow by reaction with 1,2‐ethanediamine (EDA) could remove all the NACs and SO₃^2?. The results suggested that EDA‐PSt adsorbed the NACs though multimode interactions, i.e., hydrogen bond and electrostatic attraction. After adsorption using EDA‐PSt, chemical oxygen demand (COD) was reduced from 86.1 to 11.2 mg L^?1, and a colorless, transparent, and nontoxic solution with neutral pH value was obtained. Five grams of EDA‐PSt could purify 1600 cm³ of distillate of TNT red water, and the adsorbents could be recycled by elution with methanol to desorb the neutral NACs followed by elution with 0.1 mol L^?1 NaOH to wash off 2,4‐DNP and SO₃^2?. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of syndiotactic polystyrene on the crystallization behavior of isotactic polypropylene/syndiotactic polystyrene blends with and without β‐nucleating agent

Blends of isotactic polypropylene (PP) and syndiotactic polystyrene (sPS) with and without β‐nucleating agent were prepared using a twin‐screw extruder at 290 °C. Blends of PP/sPS with β‐nucleating agent mainly show β crystalline form, irrespective of high (20 °C min^?1) or low (2 °C min^?1) previous cooling rates. This suggests that the cooling rates have little effect on the polymorphic composition of PP in PP/sPS blends. The effect of sPS on the crystallization of PP is compared with that of polyamide 6 (PA6). The increase in crystallization temperature of PP is smaller in the presence of sPS than in the presence of PA6; the fold surface free energy of PP/sPS is larger than that of PP/PA6 blends. These results reveal that compared with PA6, sPS has much weaker α‐nucleation effect on the crystallization of PP. The weak α‐nucleation effect of sPS is attributed to the high lattice mismatch between PP and sPS crystals.     

Light‐triggered reversible solubility of α‐cyclodextrin and azobenzene moiety complexes in PDMAA‐co‐PAPA via molecular recognition

Photoresponsive polymer with azobenzene pendant group (PDMAA‐co‐PAPA) was synthesized by radical polymerization of N,N‐dimethylacrylamide (DMAA) and N‐4‐phenylazophenyl acrylamide (PAPA), and the characterization of the inclusion complexes of the PDMAA‐co‐PAPA with α‐cyclodextrin (α‐CD) were performed by FTIR, GPC, ¹H NMR, 2D NOESY, and UV–vis spectroscopy. It was found that the solubility of PDMAA‐co‐PAPA and α‐CD inclusion complexes in aqueous solution showed tunable property, which could be triggered by alternating UV–vis light irradiation at a certain temperature due to the effect of molecular recognition of α‐CD with azobenzene moiety in the polymer. After UV irradiation, the lower critical solution temperature (LCST) of the polymer aqueous solution increased slightly without α‐CD while the LCST decreased sharply at presence of α‐CD. Furthermore, UV spectroscopy showed that the photoisomerization of the polymer solution went on rapidly and reversibly, and 2D NOESY data suggested that the inclusion complexation of α‐CD with trans azobenzene moiety and the decomplexation with cis azobenzene resulted in reversible solubility behavior when objected to UV and Vis light irradiation alternately. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Photo‐oxidation of polystyrene/clay nanocomposites under accelerated UV exposure: Effect on the structure and molecular weight

The present work investigates the effects of photo‐oxidation under accelerated UV conditions on the structure, the molecular weight and the morphology of polystyrene (PS)/organophilic montmorillonite (OMMT) at various clay contents: 2.5, 5, and 7 wt %. Fourier transform infrared spectroscopy, viscosimetry and scanning electron microscopy were used to evaluate the extent of degradation of nanocomposite samples in comparison with neat PS, up to 216 h of exposure. The study has shown that the formation rates of both carbonyl and hydroperoxide groups increase with exposure time, being much higher for PS/OMMT nanocomposites. Moreover, it is also observed that all samples exhibit a large increase in the scission index, however less pronounced for neat PS. These results clearly indicate the formation of low molecular weight products that could arise from chain scission. Further, the photo‐oxidation rate seems to be more affected by the presence of clay, which acts as a catalyst, rather than by the variation of clay contents. Finally, the degraded materials exhibit eroded surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Solubilization of phthalocyanines into methanol with fluoroalkyl end‐capped N‐(1,1‐dimethyl‐3‐oxobutyl)‐ and N,N‐dimethyl‐acrylamide oligomers

Self‐assembled molecular aggregates of fluoroalkyl end‐capped N‐(1,1‐dimethyl‐3‐oxobutyl)‐ and N,N‐dimethyl‐acrylamide oligomers in methanol were found to interact with phthalocyanines as guest molecules to exhibit good solubility. On the other hand, the corresponding nonfluorinated oligomers were not effective in solubilizing phthalocyanines under similar conditions. In these oligomers, fluorinated N‐(1,1‐dimethyl‐3‐oxobutyl)acrylamide oligomers were more effective in solubilizing phthalocyanines in methanol. Self‐assemblies formed by fluorinated oligomer‐phthalocyanine complexes are applied to the surface modifications of polystyrene (PS), and the modified PS surface exhibited not only a strong oleophobicity imparted by fluorine but also good hydrophilicity. Thus, these fluorinated molecular aggregate‐phthalocyanine systems are suggested to have high potential for new fluorinated functional materials through their excellent properties imparted by fluorine and phthalocyanines. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 521–525, 2004     

Facile synthesis and characterization of star‐shaped polystyrene: self‐condensing atom transfer radical copolymerization of N‐[4‐(α‐bromoisobutyryloxy)phenyl]maleimide and styrene

BACKGROUND: Generation of stars around in situ formed cores provides a facile approach to star‐shaped polymers. Therefore the self‐condensing atom transfer radical copolymerization (SCATRCP) of N‐[4‐(α‐bromoisobutyryloxy)phenyl]maleimide (BiBPM) and a large excess of styrene (St) was investigated. RESULTS: BiBPM and St formed a charge transfer complex (CTC), which underwent the SCATRCP, leading to the branched core initiating the atom transfer radical polymerization of St, finally giving star‐shaped polystyrene (PS). Kinetic and structural study showed that a higher dosage of BiBPM resulted in an enhanced polymerization rate, a higher degree of branching and a larger number of short PS arms. Differential scanning calorimetry suggested that the glass transition temperature of the star‐shaped PS decreased with molecular weight. Melt rheometry showed that even a slightly branched architecture of the PS led to a significantly lower viscosity; both the melt flow index and the activation energy increased with the degree of branching. CONCLUSION: Due to the preferential consumption of BiBPM and formation of a CTC, even a very low dosage of BiBPM could lead to star‐shaped PS, which, in comparison with linear analogues, could possess much better melt fluidity. Copyright © 2008 Society of Chemical Industry     

Improving the UV resistance of aromatic poly(1,3,4‐oxadiazole) fiber using the disperse dye modified with octavinyl POSS. Part 2: Fixing form of dye and UV resistance ability

Disperse Red 60 modified with octavinyl polyhedral oligomeric silsesquioxanes (POSS) was used to color poly(p‐phenylene‐1,3,4‐oxadiazoles) (p‐POD) fiber. The dyed p‐POD fiber was given high UV resistance and excellent color strength (K/S value) simultaneously. And the effects of the UV irradiation time on the K/S values and the strength retention of dyed fiber were investigated. The results indicated that the modified dye (1:3) molecules can easily be adsorbed on fiber surface and diffuse into fiber, whose fixing form on the fiber surface is a semiembedded type. Meanwhile, the surface morphology, the aggregation structure, the thermal property, the color fastness, and anti‐UV durability of the dyed p‐POD fiber were characterized. After UV accelerated aging, the macroscopic and microscopic structures of the dyed p‐POD fiber can well be maintained and the color fastness is also satisfactory. Meanwhile, this method also solves the problem of poor anti‐UV durability of the modified fiber with the previous processes. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44928.     

Atom transfer radical polymerization grafting of highly functionalized polystyrene and poly(4‐methylstyrene) macroinitiators with tert‐butyl acrylate

Two monodisperse graft copolymers, poly(4‐methylstyrene)‐graft‐poly(tert‐butyl acrylate) [number‐average molecular weight (M_n) = 37,500, weight‐average molecular weight/number‐average molecular weight (M_w/M_n) = 1.12] and polystyrene‐graft‐poly(tert‐butyl acrylate) (M_n = 72,800, M_w/M_n = 1.12), were prepared by the atom transfer radical polymerization of tert‐butyl acrylate catalyzed with Cu(I) halides. As macroinitiators, poly{(4‐methylstyrene)‐co‐[(4‐bromomethyl)styrene]} and poly{styrene‐co‐[4‐(1‐(2‐bromopropionyloxy)ethyl)styrene]}, carrying 40% of the bromoalkyl functionalities along the chain, were used. The dependencies of molecular parameters on monomer conversion fulfilled the criteria for controlled polymerizations. In contrast, the dependencies of monomer conversion versus time were nonideal; possible causes were examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2930–2936, 2002     

Wetting behaviour and direct observation of thermally responsive polystyrene‐block‐poly(N‐isopropylacrylamide)‐block‐polystyrene electrospun fibres in aqueous environment

Electrospun fibres of thermally responsive triblock copolymer polystyrene‐block‐poly(N‐isopropylacrylamide)‐block‐polystyrene were prepared. Fibre morphology and swelling were studied below and above the lower critical solution temperature of poly(N‐isopropylacrylamide) (PNIPAM) using cryo‐electron microscopy. Cryo‐transmission electron microscopy showed that the fibre diameter increased up to 150% after immersion in water at 20 °C. In contrast, at 45 °C the fibre diameter increased considerably less. The sessile drop technique was used to characterize temperature‐dependent wetting of fibre mats. Contact angle (θ_CA) measurements revealed that a block copolymer fibre mat changed from hydrophobic (θ_CA > 90°) to hydrophilic (θ_CA < 90°) state within seconds after applying a water droplet on it at 20 °C. At 40 °C the initial contact angle was measured to be higher (135°) and it decreased much less than at 20 °C during the first minute of measurement. We observed using scanning electron microscopy that the electrospun fibres of the block copolymer having 77 wt% of PNIPAM lost their cylindrical shape and changed from fibres to thin sheets at both 20 and 40 °C within seconds after applying water on the fibres. Fibres having 55 wt% of PNIPAM were observed to be stable in water at both 20 and 40 °C, which resulted, surprisingly, in fibre mats with the strongest effects on thermally sensitive wetting. We discuss the surprising results and the implications that the evolution of fibre surface roughness has on the long‐term wetting behaviour, demonstrating a self‐adaptable hydrophilicity/hydrophobicity nature of the fibre mats. © 2013 Society of Chemical Industry     

Preparation and Use of Polystyryl‐DABCOF2: An Efficient Recoverable and Reusable Catalyst for β‐Azidation of α,β‐Unsaturated Ketones in Water

Novel solid fluorides were prepared to optimize the β‐azidation of α,β‐unsaturated ketones. The higher loading of these catalysts compared to that of commercially available fluorides has allowed the use of a smaller mass of catalyst helping the mixing of the reaction mixture. Porous polymeric supports have proved to be more efficient in the presence of water as reaction medium. Water has played a crucial role showing a beneficial effect on the reactivity by improving dispersion of the reaction mixture and also by avoiding organic fouling caused by the retention of the reaction mixture within the polymeric matrix. This has facilitated the recovery of the products from the catalyst. The protocol reported has allowed a significant reduction in the organic solvent required for the complete recovery of the pure product whilst leaving the catalyst clean and reusable. E‐factors are in the range of 5.9–10.5 and therefore ca. 3 times smaller than previous procedures operating under solvent‐free conditions. To further improve the efficiency of our approach we have developed a protocol operating in a continuous‐flow manner that has allowed us to achieve an E‐factor of 1.7–1.9, with a reduction of ca. 80% of the corresponding batch conditions. The continuous‐flow protocol has allowed us to minimize the use of trimethylsilyl azide making the recovery and reuse of water and catalyst 5f very efficient and simple. Finally, a novel reduction system using palladium on alumina (5 mol%) and equimolar amount of formic acid has been used in the presence of 1 equivalent of di‐tert‐butyl pyrocarbonate to set a multistep protocol operating in continuous‐flow conditions for the preparation of two representative N‐Boc‐β‐amino ketones starting from the corresponding enones with E‐factors of 3.2 and 2.7, respectively.     

Synthesis of block copolymers with thermodynamically compatible chain segments: di‐ and triblock copolymers of polystyrene and poly(2,6‐dimethyl‐1,4‐phenylene oxide)

Mono‐ and bifunctional poly(phenylene oxide) (PPO) macroinitiators for atom transfer radical polymerization (ATRP) were prepared by esterification of mono‐ and bishydroxy telechelic PPO with 2‐bromoisobutyryl bromide. The macroinitiators were used for ATRP of styrene to give block copolymers with PPO and polystyrene (PS) segments, namely PPO‐block‐PS and PS‐block‐PPO‐block‐PS. Various ligands were studied in combination with CuBr as ATRP catalysts. Kinetic investigations revealed controlled polymerization processes for certain ligands and temperature ranges. Thermal analysis of the block copolymers by means of DSC revealed only one glass transition temperature as a result of the compatibility of the PS and PPO chain segments and the formation of a single phase; this glass transition temperature can be adjusted over a wide temperature range (ca 100–199 °C), depending on the composition of the block copolymer. Copyright © 2005 Society of Chemical Industry     

Relationship of structure and properties of phosphine‐containing catalysts in reactions with epoxy and phenol compounds

Triphenylphosphine (TPP) derivatives, which are catalysts of reactions with epoxy and phenol compounds, were investigated regarding the melting behavior and catalyst effect. The melting behavior was measured by differential scanning calorimetry (DSC), and the relationship of melting behavior (melting point and heat of fusion) and chemical structure were discussed using the heat of formation calculated by a semiempirical method. Two schemes are proposed for the reactions with epoxy and phenol compounds: a complex formation scheme, and an ionic scheme. The ionic scheme was the predominant route in the reactions with epoxy and phenol compounds in the bulk state at high temperature (180°C) on the basis of DSC measurements of the curing reaction and the semiempirical calculation of the heat of formation of products and partial charge of the phosphine group in the TPP derivatives. Consequently, the reaction rate of epoxy and phenol compounds decreased by introducing electron‐withdrawing substituents such as chlorine in the basic catalyst. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2335–2341, 2002     

Preparation of poly(9‐aminoacridine)‐modified electrode and its application in the determination of dopamine and ascorbic acid simultaneously

A novel modified electrode was fabricated with 9‐aminoacridine by electropolymerization in the phosphate buffer solution (PBS) (pH 7.4) and was characterized by cyclic voltammetry (CV). The modified electrode showed excellent electrocatalytic effect and high stability toward the electrochemical oxidation of dopamine (DA) and ascorbic acid (AA). Also, it showed a high stability for the determination of DA and AA simultaneously. Well‐separated voltammetric peaks were observed for DA and AA on the modified electrode. The separation of two anodic peaks was 170 mV, which was large enough to eliminate the interference of AA and determine DA. The differential pulse voltammograms (DPV) were used for the measurement of DA by means of the poly(9‐aminoacridine)‐modified electrode in PBS at pH 7.4. A linear response toDA was observed in the concentration range from 1.5 × 10^?6 to 3.5 × 10^?3 mol L^?1 with a correlation coefficient of 0.9998 and a detection limit (S/N = 3) of 1.0 × 10^?7mol L^?1. The proposed method was used to determine DA in DA‐hydrochloride injection and showed excellent sensitivity and recovery. The ease of fabrication, good reproducibility, high stability, and low cost of the modified electrode are the promising features of the proposed sensor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3864–3870, 2007     

A new model for correlation and prediction of equilibrium CO2 solubility in N‐methyl‐4‐piperidinol solvent

In this work, the equilibrium CO₂ solubility in the aqueous tertiary amine, N‐methyl‐4‐piperidinol (MPDL) was measured over a range of temperatures, CO₂ partial pressures and amine concentrations. The dissociation constant of the MPDL solution was determined as well. A new thermodynamic model was developed to predict the equilibrium CO₂ solubility in the MPDL‐H₂O‐CO₂ system. This model, equipped with the correction factor (C_f), can give reasonable prediction with an average absolute deviation of 2.0%, and performs better than other models (i.e., KE model, Li‐Shen model, and Hu‐Chakma). The second‐order reaction rate constant (k₂) of MPDL and the heat of CO₂ absorption (–ΔH_abs) into aqueous MPDL solutions were evaluated as well. Based on the comparison with some conventional amines, MPDL revealed a high‐equilibrium CO₂ loading, reasonably fast absorption rate when compared with other tertiary amines, and a low energy requirement for regeneration. It may, therefore, be considered to be an alternative solvent for CO₂ capture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3395–3403, 2017     

Metathesis of 1‐Octene in Ionic Liquids and Other Solvents: Effects of Substrate Solubility,Solvent Polarity and Impurities

With the self‐metathesis of 1‐octene to 7‐tetradecene catalyzed by Grubbs 1^st generation [benzylidene‐bis(tricyclohexylphosphine)dichlororuthenium, ( 1 )] precursor at low concentrations (0.02 mol %) as basis, the effects of the solubility of the substrate in ionic liquids, the solvent polarity, as well as the influence of various impurities stemming from the preparation of ionic liquids have been investigated. The solubility of the substrate in the ionic liquid has little effect on the conversion, and the reaction is not mass‐transfer limited. While a higher polarity of an organic solvent increases the rate, it is independent of the polarity excerted by the cation of an ionic liquid. Of paramount importance for reproducible results is the purity of ionic liquids. An extensive study shows that catalyst deactivation by impurities increases in the order of water<halide<1‐methylimidazole. In the presence of water or 1‐methylimidazole impurities, the Grubbs‐Hoveyda precursor ( 3 ) is superior to both the 1^st ( 1 ) and 2^nd ( 2 ) generation Grubbs complexes. Under impurity‐free conditions or in the presence of chloride, the performance of 2 is equivalent to that of 3 .