Synthesis and characterization of side-chain liquid crystalline homopolymers and block copolymers containing biphenyl-4-ylthiophene and biphenyl-4-ylfluorene pendants

A series of new liquid crystalline homopolymers (P1 and P2) and block copolymers (P3 and P4) composed of methacrylates containing pendant biphenyl-4-ylthiophene (M1) and biphenyl-4-ylfluorene (M2) units were synthesized by atom transfer radical polymerization (ATRP). The number-average molecular weights (M_n) of the homopolymer (P2) and diblock copolymers (P3 and P4) were in the range of 5153-8713 g mol⁻¹ with polydispersity indices (PDIs) between 1.17 and 1.25. The thermal, mesogenic, and photoluminescence (PL) properties of all polymers were investigated. Except for the absence of mesogenic properties in block copolymer P4, polymers P1 and P3 possessed the smectic A phase and polymer P2 exhibited the nematic phase. Moreover, the mesomorphism and the layer d-spacing values of the smectic A phase in polymers P1 and P3 were confirmed and characterized by X-ray diffraction (XRD) patterns.     

SG1-based alkoxyamine bearing a N-succinimidyl ester: A versatile tool for advanced polymer synthesis

This paper reports the preparation of a MAMA-SG1 (BlocBuilder™) derived alkoxyamine bearing a N-succinimidyl (NHS) ester group 1, valuable for functional and advanced polymer synthesis. This alkoxyamine was exploited following two strategies: (i) a post-functionalization approach based on the transformation of α-NHS chain ends of polymers previously obtained by nitroxide mediated polymerization (NMP) from 1 (path A) and (ii) a pre-functionalization approach based on the functionalization of alkoxyamine 1 prior to NMP (path B). Path A was demonstrated by derivatization of α-NHS functionalized polystyrenes with ethanolamine, yielding hydroxyl-functionalized polystyrenes. Path B was illustrated by two examples: first, a OH functional alkoxyamine initiator, prepared by reaction of 1 with ethanolamine, was used for the synthesis of polystyrene-b-poly(d,l-lactide) by combining NMP and ring-opening polymerization. Secondly, a poly(propylene oxide)-SG1 macroalkoxyamine, obtained from reaction of 1 with NH₂-functionalized poly(propylene oxide), was used as a macroinitiator for NMP of styrene to obtain a PS-b-PPO block copolymer.     

Synthesis of random and block copolymers of styrene and styrenesulfonic acid with low polydispersity using nitroxide-mediated living radical polymerization technique

Poly(styrene-ran-styrenesulfonic acid) and poly(styrene-block-styrenesulfonic acid) with low polydispersity were prepared using nitroxide-mediated living radical polymerization technique. Random or block copolymerization of styrene and neopentyl p-styrenesulfonate smoothly proceeded by AIBN/2,2,5,5-tetramethyl-4-diethylphosphono-3-azahexane-3-nitroxide initiating system. Transformation of the sulfonate ester to sulfonic acid was carried out by the reaction with trimethylsilyl iodide or by thermolysis at 150 °C. Those polymers showed amphiphilic characters.     

The amphiphilic block copolymers of 2-(dimethylamino)ethyl methacrylate and methyl methacrylate: Synthesis by atom transfer radical polymerization and solution properties

Amphiphilic di- and tri-block copolymers of poly(methyl methacrylate) (PMMA) and poly(2-dimethylamino)ethyl methacrylate (PDMAEMA) have been synthesized by atom transfer radical polymerization (ATRP) at ambient temperature (35 °C) in the environment-friendly solvent, aqueous ethanol (water 16 vol%) using CuCl/o-phenanthroline as the catalyst. The PDMAEMA blocks are contaminated with ethyl methacrylate (EMA) residues to the extent of 1-2 mol% of DMAEMA depending on the length of the PDMAEMA block. The EMA forms through the autocatalyzed ethanolysis of the DMAEMA monomer and undergoes random copolymerization with the latter. The rate of ethanolysis is unexpectedly greater in the aqueous ethanol than in neat ethanol, which has been attributed to the higher polarity of the former than of the latter. In contrast to the ethanolysis no hydrolysis of DMAEMA in the aqueous ethanol medium could be detected for 133 h. The block copolymers form micelles in water. Their solubility and CMC in neutral water have been studied. Dynamic light scattering (DLS) studies reveal that for a fixed degree of polymerization (DP) of the PMMA block the hydrodynamic diameter of the micelles in methanolic water (water 95 vol%) increases at a faster rate with the DP of the PDMAEMA block when it is much greater than that of the PMMA block compared to when it is less than or close to that of the latter.     

A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator

Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)₂] works under reverse ATRP conditions.     

羟化含氟嵌段共聚物的合成及其自组装行为研究

用α-溴代丙酸乙酯（EPN—B）／氯化亚铜（CuCl）／联二吡啶（bpy）作为催化引发体系,环己酮为溶剂,进行甲基丙烯酸2,2,2-三氟乙酯（TFEMA）的原子转移自由基聚合（ATRP）,得到单分散PTFEMA—X预聚体。并以此预聚体为大分子引发剂引发甲基丙烯酸-β-羟乙酯聚合,得到分子质量可控、分子质量分布窄的聚甲基丙烯酸2,2,2-三氟乙酯-b-聚甲基丙烯酸-β-羟乙酯嵌段共聚物,用FTIR、^1H—NMR、GPC等对产物的结构与性能进行了表征。同时利用动态激光光散射（DLS）对嵌段共聚物的自组装行为进行了研究。     

Incorporation of benzothiadiazole moiety at junction of polyfluorene–polytriarylamime block copolymer for effective color tuning in organic light emitting diode

Block copolymer consisting of polyfluorene and polytriarylamine with benzothiadiazole moiety at the junction is prepared in order to obtain an orange emitting polymer via Suzuki‐Miyaura followed by Buchwald‐Hartwig coupling reactions. Electroluminescent device fabricated with resulting block copolymer exhibit only orange emission, although slight blue emission is observed in the fluorescent spectrum for the thin film, indicating that benzothiadiazole part plays a role of an effective trap site. Devices based on polyfluorene homopolymer doped with block copolymer (10 wt %) or an orange emitting model compound at the corresponding content of benzotiadiazole unit are also fabricated. The device with the model compound exhibits orange emission with Commission Internationale de l'Éclairage (CIE) coordinate of (0.58, 0.42), whereas that with block copolymer pale orange with the coordinate of (0.44, 0.38). This fact is probably due to the preferential distribution of block copolymer at the vicinity of anode via hydrophilic interaction of trioxyethylene side chains with poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45393.     

Synthesis of acetophenone formaldehyde resin containing ABA type block copolymers by ATRP

Well‐defined ABA type block copolymers of acetophenone formaldehyde resin (AFR) and methyl methacrylate (MMA) were synthesized via atom transfer radical polymerization. In the first step, acetophenone formaldehyde resin containing hydroxyl groups was modified with 2‐bromopropionyl bromide. Resulting difunctional macroinitiator was used in the ATRP of MMA using copper bromide (CuBr)/N,N,N′,N″,N″‐pentamethyl‐diethylenetriamine (PMDETA) as the catalyst system at 90°C. The chemical composition and structure of the copolymers were characterized by nuclear magnetic resonance (¹H‐NMR) spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy, and molecular weight measurement. Gel permeation chromatography (GPC) was used to study the molecular weight distributions of the AFR block copolymers. M_n up to 24,000 associated with narrow molecular weight distributions (PDI < 1.5) were obtained with conversions up to 79%. Coating properties of obtained block copolymers such as adhesion and reflectance values were investigated. They showed good adhesion properties on Plexiglass substrates. Reflectance values increased as the resin content of polymer increased. The thermal properties of all polymers were studied using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). All block copolymers showed higher thermal stability than their precursor AFR resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis of poly(trioctylammonium p-styrenesulfonate) homopolymers and block copolymers by RAFT polymerization

A method to prepare sulfonated polystyrene-containing block copolymers has been investigated by neutralizing styrene sulfonic acid with trioctylamine to produce the hydrophobic monomer trioctylammonium p-styrenesulfonate (SS-TOA). This monomer was polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization to produce PSS-TOA homopolymers. A PSS-TOA homopolymer was then used as a macro-RAFT agent for the polymerization of styrene to prepare poly(trioctylammonium p-styrenesulfonate)-block-poly(styrene) (PSS-TOA-b-PS). These block copolymers could be ion-exchanged to produce either the hydrophilic sodium salt form of PSS or a hydrophobic quaternary ammonium salt. This approach will be useful for preparing PSS-containing block copolymers with a range of hydrophobic blocks for applications such as ion-exchange membranes.     

Precise synthesis of polymers containing functional end groups by living ring-opening metathesis polymerization (ROMP): Efficient tools for synthesis of block/graft copolymers

This article summarizes recent examples for precise synthesis of (co)polymers containing functional end groups prepared by living ring-opening metathesis polymerization (ROMP) using molybdenum, ruthenium complex catalysts. In particular, this article reviews recent examples for synthesis of amphiphilic block/graft copolymers by adopting transition metal-catalyzed living ROMP technique. Unique characteristics of the living ROMP initiated by the molybdenum alkylidene complexes (so-called Schrock type catalyst), which accomplish precise control of the block segment (hydrophilic and hydrophobic) as well as exclusive introduction of functionalities at the polymer chain end, enable us to provide the synthesis of block copolymers varying different backbones by adopting the “grafting to” or the “grafting from” approach as well as “soluble” star shape polymers with controlled manner. The “grafting through” approach (polymerization of macromonomers) by the repetitive ROMP technique offers precise control of the amphiphilic block segments.     

Block and star block copolymers by mechanism transformation. VIII Synthesis and characterization of triblock poly(LLA-b-St-b-MMA) by combination of ATRP and ROP

Block copolymers, poly(LLA-b-St)s and triblock copolymes, poly(LLA-b-St-b-MMA)s have been synthesized by the combination of the atom transfer radical polymerization (ATRP) with ring-opening polymerization (ROP) using bifunctional initiator β-hydroxylethyl α-bromoisobutyrate (HEBIB) without intermediate function transformation. The molecular weight (MW) and the molecular weight distribution (MWD) can be controlled. The structures of the copolymers were confirmed by ¹H NMR spectroscopy and GPC.     

Trapping polystyrene radicals using nitrones: Synthesis of polymers with mid-chain alkoxyamine functionality

Polystyrene radicals were formed in the presence of NtBPN under a variety of reaction conditions and reactant ratios, forming polymer dimers of twice the molecular weight of the monobrominated polystyrene (PStBr) precursors. The polystyrene radicals were generated by the activation of the monohalogentated polystyrene precursors, prepared by atom transfer radical polymerization (ATRP). The extent of radicals trapped by the nitrone, and therefore containing mid-chain alkoxyamine functionality, was determined by thermolysis of the polymer dimers, with the C-O bond in this functionality being cleaved and reverting the chains back to the approximate size of the precursors. Polymer dimers could also be formed simply by radical-radical combination of the chain-ends, which is conventional atom transfer radical coupling (ATRC) and thus contains a head-to-head C-C bond, rendering them inert to thermolysis under conditions that cleave the C-O bond. It was found that near quantitative alkoxyamine mid-chain functionality could be achieved by activating the PStBr in the presence of 10 equivalents of nitrone, 5 equivalents of copper bromide, and 2 equivalents of copper metal. Further reducing the amount of copper metal led to incomplete coupling, while increasing the equivalents beyond 2 generated polymer dimers with less than quantitative mid-chain functionality. Monochlorinated polystyrene (PStCl) precursors gave much poorer coupling results compared to reactions with PStBr, which is consistent with the stronger C-Cl bond resisting activation and the formation of the polystyryl radicals.     

Comparison of thermomechanical properties of statistical, gradient and block copolymers of isobornyl acrylate and n-butyl acrylate with various acrylate homopolymers

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure-property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (T_g) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single T_g, block copolymers showed two T_gs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.     

Effect of block compositions of amphiphilic block copolymers on the physicochemical properties of polymeric micelles

Amphiphilic block copolymers with various chain lengths of poly(n-butyl methacrylate) blocks (PBMA) and poly(N-acryloylmorpholine) blocks (PAM) were prepared by RAFT polymerization. Packing parameter of block polymers in water (β < 0.2) indicated the formation of core-corona structures, which was further confirmed from a difference between core- and corona-forming chain surface areas. Hydrodynamic micellar size was related with the numbers of BMA (N_BMA) and AM (N_AM), and their ratios (N_BMA/N_AM). With increasing N_BMA/N_AM value, the polymer aggregation numbers and inner core sizes increased, while the critical micelle concentrations, the corona thickness, and the second virial coefficient of block copolymer micelles decreased. These properties changed with increasing N_BMA/N_AM value resulted in a linear increase in corona chain unit density (ρ_AM) that limited chain mobility. Thus, the interaction between the micelles and serum protein at low ρ_AM disappeared at a higher value. Consequently, both micellar properties and biocompatible effect can be regulated by tailoring the block compositions of amphiphilic polymers.     

A study of light‐emitting diodes constructed with copolymers having cyclohexyl thiophene and hexyl thiophene units

We report visible light emission from a diode made from copolymers of 3‐alkylthiophenes. These chemically synthesized copolymers exhibit improved electroluminescence and quantum efficiencies compared to poly (3‐cyclohexylthiophene). Good solubility of copolymers allows the fabrication of the light emitting diodes by spin‐cast polymer film. The devices emit greenish‐blue light in wavelength region of 550–580 nm, which is easily visible in poorly lighted room. The quantum efficiencies are in the range of 0.002 to 0.01% (photons per electron) at room temperature; which are significantly higher than corresponding values for poly(3‐cyclohexylthiophene) based light emitting diodes. The charge carrier mobility in the device is found to be 5.6 × 10⁻⁴ cm²/Vs. ©2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1051–1055, 2000     

含端基氯低聚物引发剂的合成及其引发苯乙烯聚合的研究

通过对４种端羟基低聚物进行氯乙酰化反应,制备了一系列含端基氯的低聚物,然后以这些含端基氯的低聚物为大分子引发剂,在ＣｕＣｌ／ｂｐｙ存在下引发苯乙烯的ＡＴＲＰ反应,得到ＡＢＡ嵌段共聚物。用＾１Ｈ－ＮＭＲ分析证明了聚合物的嵌段结构,以ＳＥＣ测定了聚合物的相对分子质量及其分布,发现嵌段聚合物的相对分子质量和单体转化率成正比,并和相对分子质量的理论值Ｍ↑－ｎ,ｔｈ＝（Δ［Ｍ］／［ｏｌｉｇｏｍｅｒ－Ｃｌ］）     

Synthesis of POSS-containing fluorosilicone block copolymers via RAFT polymerization for application as non-wetting coating materials

By using a polydimethylsiloxane (PDMS) macro-chain transfer agent with trithiocarbonate groups at both ends, fluorosilicone block copolymers containing polyhedral oligomeric silsesquioxane (POSS) were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. Acryloisobutyl POSS (APOSS) and 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) were sequentially introduced into the copolymers. The obtained triblock copolymers PDMS-b-(PAPOSS)₂ exhibited a low polydispersity index (PDI) of less than 1.42 in the first 6 h of polymerization, but the PDI value became broader later because of the steric hindrance of the POSS macromer. The POSS-containing fluorosilicone pentablock copolymers with a PDI of about 2.0, which were prepared by the further RAFT polymerization of HFBA, showed clear microphase separation. The average roughness values of the copolymer films were enhanced by introducing POSS, and a certain POSS content led to a significant decrease of the receding contact angle. Measurements of water contact angles and ice shear strengths demonstrated that the non-wetting properties of the copolymer films were improved by the incorporation of both POSS and fluorine blocks. The block copolymers combine the advantages of POSS, PDMS and fluoropolymers, and can be potentially applied as non-wetting coating materials for anti-icing or anti-frosting.     

A facile synthesis of sulfonated poly(diphenylamine) and the application as a novel hole injection layer in polymer light emitting diodes

Water-soluble sulfonated poly(diphenylamine) (SPDPA) was synthesized and applied as a hole injection layer (HIL). It was characterized in terms of ¹H NMR, ¹³C NMR, elemental analysis (EA), UV-vis, Raman, ultraviolet photoelectron spectroscopies (UPS) and TGA thermal stability measurement. The high transparency in visible region and acceptable conductivity were beneficial as HIL material. The topographic image obtained from Atomic Force Microscope shows that the surface of SPDPA-coated indium tin oxide (ITO) is smoother than that of bare ITO. Raman spectra indicate that SPDPA possesses the higher oxidation and doping level due to SO₃H group on the phenyl ring, rendering SPDPA the higher work function with 0.35 eV than PDPA from UPS spectra. The electroluminescence efficiency of polymer light emitting diode using poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) as an active layer and SPDPA as HIL can be reached 2.0 cd/A, showing the slightly better performance than that using PEDOT:PSS as HIL.     

Synthesis of liquid crystalline–amorphous block copolymers by combination of CFRP and ATRP mechanisms

Block copolymers of liquid crystalline 6‐(4‐cyanobiphenyl‐4′‐oxy) hexyl acrylate (LC6) and styrene (St) were obtained by the combination of two different free‐radical polymerization mechanisms namely conventional free‐radical polymerization (CFRP) and atom transfer radical polymerization (ATRP). In the first part, thermosensitive azo alkyl halide, difunctional initiator (AI), was prepared and then used for CFRP of LC6 monomer. The obtained bromine‐ended difunctional liquid crystalline polymers (PLC6) were used as initiators in ATRP of St, in bulk in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as catalyst. In the second part, AI was firstly polymerized by CFRP in the presence of St and then the obtained difunctional bromine ended polystyrenes (PSt) were used as initiators in ATRP of LC6 in diphenyl ether solvent in conjuction with CuBr/PMDETA. The spectral, thermal, and optical measurements confirmed a fully controlled living polymerization, which results in formation of ABA‐type block copolymers with very narrow polydispersities. In both cases, blocks of the different chemical composition were segregated in the solid and melt phases. The mesophase transition temperatures of the liquid crystalline block were found to be very similar to those of the corresponding homopolymers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006