Poly(hydroxyether of bisphenol A)-block-polydimethylsiloxane alternating block copolymer and its nanostructured blends with epoxy resin

Mannich condensation was utilized to synthesize poly(hydroxyether of bisphenol A)-block-polydimethylsiloxane alternating block copolymer (PH-alt-PDMS). The polymerization between the phenolic hydroxyl-terminated oligo(hydroxyether of bisphenol A) and amino-terminated oligodimethylsiloxane with the defined lengths was carried out via the formation of benzoxazine ring linkages, which was mediated with paraformaldehyde. The alternating block copolymer was characterized by means of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). The block copolymer was incorporated to prepare nanostructured thermosetting blends. The nanostructures of the thermosetting blends were investigated by means of atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). The formation of the nanostructures in the thermosetting composites was judged to follow the self-assembly mechanism in terms of the difference in miscibility of PDMS and PH subchains with epoxy resin after and before curing reaction. The fracture toughness of the nanostructured blends was evaluated in terms of the measurement of stress field intensity factor (K_IC). It is noted that the epoxy resin was significantly toughened.     

Toughening of polyamide‐6 with little loss in modulus by block copolymer containing poly(styrene‐alt‐maleic acid) segment

Toughening of polyamide‐6 (PA6) by elastomers without sacrificing the modulus of blends has always been a challenge. In this study, PA6 was modified by poly(styrene‐alt‐maleic acid)‐block‐polystyrene‐block‐poly(n‐butyl acrylate)‐block‐polystyrene tetrablock copolymer (BCP) elastomer. The introduced acid groups in BCP resulted in the size of BCP inclusions down to nanometers in polyamide matrix. 10 wt % of BCP‐modified PA6 blends achieved five times increase in notched impact strength with almost no loss in modulus. Microscopic observations suggested the cavitation of elastomer particles and shear yielding of PA6 matrix to be the major toughening mechanism. This research provides a strategy to toughen polyamides by block copolymers at very low rubber content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44849.     

Synthesis and characterization of poly(4‐diphenylaminostyrene)‐Poly(9‐vinylanthracene) binary block copolymer

Block copolymerization of plural types of monomers offers a new opportunity for the preparation of a variety of multifunctional polymers. Poly(4‐diphenylaminostyrene) (PDAS)‐poly(9‐vinylanthracene) (PVAN) binary block copolymer (PDAS‐PVAN) was synthesized by (living) anionic polymerization using the benzyllithium/N,N,N′,N′‐tetramethylethylenediamine system. The photoluminescence emission of PDAS‐PVAN was enhanced by the fluorescence resonance energy transfer from PDAS block to PVAN block in PDAS‐PVAN. The hole drift mobility of the copolymer was controllable by the amount of triphenylamino groups in the polymer chain. The optical and electrical properties of PDAS‐PVAN were adjustable through the polymer chain structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of well‐defined block copolymer having one polystyrene segment and another poly(styrene‐alt‐maleic anhydride) segment with RAFT polymerization

Block copolymers, polystyrene‐b‐poly(styrene‐co‐maleic anhydride), have been prepared by reversible addition‐fragmentation chain transfer (RAFT) polymerization technique using three different approaches: 1‐phenylethyl phenyldithioacetate (PEPDTA) directly as RAFT agent, mediated polystyrene (PS) block as the macromolecular PS‐RAFT agent and mediated poly(styrene‐maleic anhydride) (SMA) block with alternating sequence as the macromolecular SMA‐RAFT agent. Copolymers synthesized in the one‐step method using PEPDTA as RAFT agent possess one PS block and one SMA block with gradient structure. When the macromolecular RAFT agents are employed, copolymers with one PS block and one alternating SMA block can be produced. However, block copolymers with narrow molecular weight distribution (MWD) can only be obtained using the PS‐RAFT agent. The MWD deviates considerably from the typical RAFT polymerization system when the SMA is used as the RAFT agent. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Application of the biodegradable diblock copolymer poly(L‐lactide)‐block‐poly(L‐cysteine): Drug delivery and protein conjugation

A novel approach to self‐assembled and shell‐crosslinked (SCL) micelles from the diblock copolymer poly(L ‐lactide)‐block‐poly(L ‐cysteine) to be used as drug and protein delivery carriers is described. Rifampicin was used as a model drug. The drug‐loaded SCL micelles were obtained by self‐assembly of the copolymer in the presence of the drug in aqueous media. Their morphology and size were studied with dynamic light scattering and field emission scanning electron microscopy. The rifampicin loading capacity and encapsulation efficiency were studied with ultraviolet–visible spectrophotometry. The drug‐release rate in vitro depended on the oxidizing and reducing environment. Moreover, a straightforward approach to the conjugation of the copolymer with bovine serum albumin (BSA) was developed, and a gel electrophoresis test demonstrated that this conjugated BSA could be reversibly released from the copolymer substrate under reducing conditions. In conclusion, this L ‐cysteine copolymer can be used in drug delivery and in protein fixation and recovery. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and electroluminescent properties of a novel copolymer with short alternating conjugated and non‐conjugated blocks

A new electroluminescent copolymer [poly(1,5‐di(3,5‐dimethyloxystyrylene)naphthalene‐block‐tri(ethylene oxide)) (DSN–TEO)], containing alternating rigid, conjugated light‐emitting units and flexible tri(ethylene oxide) ionic conductive units, was synthesized via the Wittig reaction. The polymer has fairly good solubility in chloroform, tetrahydrofuran, toluene, etc, and excellent film‐forming ability. The decomposition temperature and the glass transition temperature were 409 °C and 42.2 °C, respectively. A light‐emitting diode (LED) device with configuration ITO/PEDOT–PSS/DSN–TEO/Ca(Al) and light‐emitting electrochemical cell (LEC) device with ITO/DSN–TEO + PEO (LiTf)/Al were prepared, and the photoluminescence and electroluminescence (EL) properties were investigated. Efficient blue‐green light emission (EL maximum emissive wavelength at 508 nm) was found with onset voltage at 6 V. The maximum light efficiency was 0.107 cd A^?1 at 20 V for LED, and the onset voltage 2.5 V and the maximum light efficiency was 4.2 cd A^?1 at 2.8 V for LEC, respectively. The response time of the LEC was less than 5 s. The EL efficiency of LEC device was improved by 44 as compared with the relative LED device. © 2003 Society of Chemical Industry     

Poly(styrene‐co‐N‐butylmaleimide) macroinitiators by controlled autopolymerization and related block copolymers

Autopolymerization of styrene‐N‐butylmaleimide mixtures at 125 or 140°C in the presence of a stable nitroxyl radical [2,2,6,6‐tetramethylpiperidin‐1‐yloxyl (TEMPO)] was found to proceed in a pseudoliving manner. Unimolecular initiators, which were originated by trapping self‐generated radical species with TEMPO, took part in the process. Under the studied experimental conditions, the TEMPO‐controlled autopolymerization with a varying comonomer ratio provided virtually alternating copolymers of narrow molecular weight distributions. The molecular weights of the copolymers increased with conversions. The obtained styrene‐N‐butylmaleimide copolymers containing TEMPO end groups were used to initiate the polymerization of styrene. The polymerization yielded poly(styrene‐co‐N‐butylmaleimide)‐polystyrene block copolymers with various polystyrene chain lengths and narrow molecular weight distributions. The compositions, molecular weights, and molecular weight distributions of the synthesized block copolymers and the initial poly(styrene‐co‐N‐butylmaleimide) precursors were evaluated using nitrogen analysis, gel permeation chromatography, and ¹H‐ and ¹³C‐NMR spectroscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2378–2385, 1999     

Influence of semi‐crystalline poly(ε‐caprolactone) and non‐crystalline polylactide blocks on the thermal properties of polydimethylsiloxane‐based block copolymers

Poly(A)‐block‐poly(B), poly(A)‐block‐poly(B)‐block‐poly(A) and B(A)₂ block copolymers were prepared through coordinated anionic ring‐opening polymerization of ε‐caprolactone (CL) and lactic acid (LA) using hydroxy‐terminated polydimethylsiloxane (PDMS) as initiator. A wide range of well‐defined combinations of PDMS‐block‐PCL and PDMS‐block‐PLA diblock copolymers, PCL‐block‐PDMS‐block‐PCL and PLA‐block‐PDMS‐block‐PLA triblock copolymers and star‐PDMS(PCL)₂ copolymers were thus obtained. The number‐average molar masses and the structure of the synthesized block copolymers were identified using various analytical techniques. The thermal properties of these copolymers were established using differential scanning calorimetry. Considering PDMS‐block‐PCL copolymers, the results demonstrate the complex effect of polymer architecture and PCL block length on the ability of the PDMS block to crystallize or not. In the case of diblock copolymers, crystallization of PCL blocks originated from stacking of adjacent chains inducing the extension of the PDMS block that can easily crystallize. In the case of star copolymers, the same tendency as in triblock copolymers is observed, showing a limited crystallization of PDMS when the length of the PCL block increases. In the case of PDMS‐block‐PLA copolymers, melting and crystallization transitions of the PLA block are never observed. Considering the diblock copolymers, PDMS sequences have the ability to crystallize. © 2019 Society of Chemical Industry     

Poly(ethylene oxide)‐based block copolymer electrolytes for lithium metal batteries

Nanostructured block copolymer electrolytes (BCEs) based on poly(ethylene oxide) (PEO) are considered as promising candidates for solid‐state electrolytes in high energy density lithium metal batteries (LMBs). Because of their self‐assembly properties, they confer on electrolytes both high mechanical strength and sufficient ionic conductivity, which linear PEO cannot provide. Two types of PEO‐based BCEs are commonly known. There are the traditional ones, also called dual‐ion conducting BCEs, which are a mixture of block copolymer chains and lithium salts. In these systems, the cations and anions participate in the conduction, inducing a concentration polarization in the electrolyte, thus leading to poor performances of LMBs. The second family of BCEs are single‐lithium‐ion conducting BCEs (SIC‐BCEs), which consist of anions being covalently grafted to the polymer backbone, therefore involving conduction by lithium ions only. SIC‐BCEs have marked advantages over dual‐ion conducting BCEs due to a high lithium ion transference number, absence of anion concentration gradients as well as low rate of lithium dendrite growth. This review focuses on the recent developments in BCEs for applications in LMBs with particular emphasis on the physicochemical and electrochemical properties of these materials. © 2018 Society of Chemical Industry     

Impact resistance of fibrous glass reinforced plastics using polycarbonate‐polydimethylsiloxane block copolymer

By using reactive polydimethylsiloxanes that have phenolic hydroxyl groups at the ends of the chain, a polycarbonate‐polydimethylsiloxane (PC‐PDMS) block copolymer was prepared, and the properties of fibrous glass reinforced plastics (GF‐PC) using this copolymer were examined. The Izod impact value of the PC‐PDMS/GF composite increases with an increase in the degree of polymerization of reactive PDMS (n) between 40 and 160. When n is 40, the Izod impact value of the PC‐PDMS/GF composite is equal to that of the PC/GF composite. The Izod impact value is independent of the PDMS content of the copolymer when it is between 2 and 4 wt %. The PC‐PDMS/GF composite is superior, in the balance between fluidity and impact resistance, to the PC/GF composite. From the results of SEM, adhesion between the polymer and GF of the PC‐PDMS/GF composite is superior to that of the PC/GF composite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1123–1127, 2002     

Preparation and kinetic analysis of PS‐b‐PBA block copolymer by 4‐oxo‐TEMPO capped polystyrene macroinitiators

Polystyrene‐block‐poly(n‐butyl acrylate) block copolymers were prepared from 4‐oxo‐2,2,6,6‐tetramethylpiperidinooxy (4‐oxo‐TEMPO) capped polystyrene macroinitiators at a high temperature, 165°C. It was found that the number‐average molecular weight of PBA chains in block copolymers could reach above 10,000 rapidly at early stage of polymerization with a narrow polydispersity index of 1.2–1.4, but after that, the polymerization seemed to be retarded. Furthermore, according to the kinetic analysis, the concentration of 4‐oxo‐TEMPO was increased mainly by the hydrogen transfer reaction of hydroxylamine (4‐oxo‐TEMPOH) to growing radicals during polymerization. This increase in 4‐oxo‐TEMPO concentration could retard the growth of polymer chains. The rate constant of the hydrogen transfer reaction of 4‐oxo‐TEMPOH to growing radicals, k_H, estimated by the kinetic model is about 9.33 × 10⁴M^‐1s^?1 at 165°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

双亲嵌段共聚物PSt-b-P(St-alt-MA)-b-PAA的自组装行为

以三硫代碳酸二(α, α'-二甲基-α-乙酸)酯(BDATC)为链转移剂, 以苯乙烯、马来酸酐、丙烯酸为原料, 通过可逆加成-断裂链转移(RAFT)合成了双亲嵌段共聚物PSt-b-P(St-alt-MA)-b-PAA。通过选择性溶剂N, N-二甲基甲酰胺(DMF)诱导聚合物进行自组装, 利用紫外-可见光光度仪、纳米激光粒度仪详细研究了共聚物中亲疏水嵌段长度、初始浓度、体系pH值对聚合物自组装行为的影响。通过化学交联的方法制备得到了聚合物交联胶束, 利用透射电镜表征了形貌与尺寸, 研究明确了其形状和尺寸的稳定性。结果表明, 上述因素均会影响共聚物的自组装行为和自组装胶束的形态, 经乙二胺交联得到的交联自组装胶束平均粒径为145.4nm, 并具有良好的形状和尺寸稳定性。     

Preparation and characterization of amphiphilic block copolymer of polyacrylonitrile‐block‐poly(ethylene oxide)

The synthesis of polyacrylonitrile‐block‐poly(ethylene oxide) (PAN‐b‐PEO) diblock copolymers is conducted by sequential initiation and Ce(IV) redox polymerization using amino‐alcohol as the parent compound. In the first step, amino‐alcohol potassium with a protected amine group initiates the polymerization of ethylene oxide (EO) to yield poly(ethylene oxide) (PEO) with an amine end group (PEO‐NH₂), which is used to synthesize a PAN‐b‐PEO diblock copolymer with Ce(IV) that takes place in the redox initiation system. A PAN‐poly(ethylene glycol)‐PAN (PAN‐PEG‐PAN) triblock copolymer is prepared by the same redox system consisting of ceric ions and PEG in an aqueous medium. The structure of the copolymer is characterized in detail by GPC, IR, ¹H‐NMR, DSC, and X‐ray diffraction. The propagation of the PAN chain is dependent on the molecular weight and concentration of the PEO prepolymer. The crystallization of the PAN and PEO block is discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1753–1759, 2003     

Biodegradable poly(L‐lactide) and polycaprolactone block copolymer networks

New biodegradable block copolymer networks were synthesized from methacrylate‐terminated poly(L ‐lactide) (mLA) and polycaprolactone (mCL) macromers. This allowed the realization of a series of materials in which the macromer ratio can be used to tailor the physical and mechanical properties of the materials. The synthesis of the macromers was characterized using Fourier transform infrared (FTIR) spectroscopy and ¹H NMR spectroscopy. Poly(mCL) and poly(mLA) networks were prepared by photopolymerization of the macromers, and copolymers were also prepared from the two macromers in various proportions. The phase microstructure of the new systems and the network architecture were investigated using differential scanning calorimetry, FTIR spectroscopy, dynamic mechanical analysis and thermogravimetry studies. Copyright © 2010 Society of Chemical Industry     

Morphology and thermomechanical properties of epoxy thermosets modified with polysulfone‐block‐polydimethylsiloxane multiblock copolymer

Polysulfone‐block‐polydimethylsiloxane (PSF‐b‐PDMS) multiblock copolymer was synthesized via the Mannich polycondensation between phenolic hydroxyl‐terminated polysulfone and aminopropyl‐terminated polydimethylsiloxane in the presence of formaldehyde. The multiblock copolymer was characterized by means of nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC) and used as a modifier to improve the thermomechanical properties of epoxy thermosets. Transmission electron microscopy (TEM) showed that the epoxy thermosets containing PSF‐b‐PDMS multiblock copolymer possesses the microphase‐separated morphological structures. Depending on the content of the PSF‐b‐PDMS multiblock copolymer, the spherical particles with the size of 50–200 nm in diameter were dispersed into the continuous epoxy matrices. The measurement of static contact angles showed that with the inclusion of PSF‐b‐PDMS multiblock copolymer, the epoxy thermosets displayed the improved surface hydrophobicity. It is noted that the epoxy resin was significantly toughened in terms of the measurement of critical stress field intensity factor (K_1C). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of hexafluoroisopropylidene bisphenol poly(arylene ether sulfone) and polydimethylsiloxane segmented block copolymers

A series of hexafluoroisopropylidene bisphenol poly(arylene ether sulfone) (BAF PAES) segmented block copolymers with varying fractions of polydimethylsiloxane (PDMS) were synthesized by a condensation reaction of hydroxyl-terminated BAF PAES and dimethylamino endcapped PDMS. The segmented block copolymers have high thermal stability. The BAF PAES homopolymer exhibits a tensile modulus of 1700 MPa and an elongation at break of 16%. Copolymerizing BAF PAES with increasing molecular weight amounts of PDMS results in tensile properties ranging from plastic to elastomeric where the elongation is 417% for a segmented block copolymer with 64 wt% PDMS incorporated. The morphological properties of these segmented block copolymers were characterized by atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). AFM and TEM images show the segmented block copolymers were microphase separated, and comparison with bisphenol A (BA) PAES-b-PDMS segmented block copolymers revealed complex differences between the morphological behavior of the two systems. SAXS data of the segmented block copolymers supports AFM and TEM images, indicating microphase separation but little long-range order.     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Synthesis and electroluminescence properties of a novel poly(paraphenylene vinylene)‐based copolymer with tri(ethylene oxide) segments on the backbone

A novel light‐emitting copolymer [tri(ethylene oxide)–poly(paraphenylene vinylene) (TEO–PPV)] containing alternating rigid, conjugated distyrylbenzene [poly(paraphenylene vinylene) model oligomer] as light‐emitting units and flexible tri(ethylene oxide) as ionic conductive units was synthesized. The polymer was characterized with Fourier transform infrared, ¹H‐NMR, ultraviolet–visible spectroscopy, differential scanning calorimetry, and gel permeation chromatography. TEO–PPV has excellent solubility in conventional organic solvents such as tetrahydrofuran, chloroform, benzene, and toluene. The estimated lowest unoccupied molecular orbital, highest occupied molecular orbital, and band gap are 2.35, 5.29, and 2.94 eV, respectively. Single‐layer and double‐layer light‐emitting diodes with indium tin oxide anodes and calcium cathodes were fabricated, and the photoluminescence (PL) and electroluminescence (EL) properties were investigated. The maximum EL emissive peak (475 nm) of the devices is essentially the same as that of PL. Anomalous current–voltage characteristics were observed in both devices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2195–2200, 2002     

Synthesis of poly(paraphenylene vinylene)—polystyrene‐based rod‐coil block copolymer by atom transfer radical polymerization: Toward a self‐organized lamellar semiconducting material

Atom transfer radical polymerization (ATRP) was used as a versatile route to well‐defined poly(diethylhexyl‐p‐phenylenevinylene‐b‐styrene) (PPV‐b‐PS) semiconducting block copolymers. For this purpose, original conjugated macroinitiators were synthesized from DEH‐PPV and further used for the copolymerization reaction. The microphase‐separated morphologies obtained with the semiconducting PPV‐b‐PS block copolymer fulfill the basic structural requirements required to build efficient organic photovoltaic devices. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008