Self-assembly of linear ABC coil-coil-rod triblock copolymers

Self-assembly of linear ABC coil-coil-rod triblock copolymer melt is studied by applying self-consistent-field lattice techniques in three-dimensional (3D) space. In contrast to rod-coil diblock copolymers, our results reveal the effect of the broad parameter space on the self-assembly of the linear ABC coil-coil-rod triblock copolymers. Seven stable structures are found stable, including “two-color” lamella, “three-color” lamella, “two-color”-perforated lamella, “three-color”-perforated lamella, core-shell hexagonal lattice phase, strip, and micelle. When the two coil blocks have equal lengths (f_A = f_B), the lamellar structure dominates the majority of the phase diagram. The effects of the two coil blocks on the self-assembly are explored by tuning the relative length of the A and B coil blocks in terms of keeping the length of the block C (rod). Moreover, by switching the position of the blocks B and C, the influence of the block sequencing on the self-assembly is studied.     

Synthesis of biodegradable and biocompatible ABC triblock copolymers

A facile approach is offered to synthesize well‐defined amphiphilic ABC triblock copolymers composed of poly(ethylene glycol) monomethyl ether (MPEO) as A block, poly(L ‐lysine) (PLLys) as B block, and poly(ε‐caprolactone) (PCL) as C block by a combination of ring‐opening polymerization (ROP) and click reactions. The propargyl‐terminated poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) diblock copolymers were synthesized via the ring‐opening polymerization of N^ε‐carbobenzoxy‐L ‐lysine N‐carboxyanhydride (Z‐L ‐Lys NCA) in DMF at room temperature using propargyl amine as an initiator and the resulting amino‐terminated poly(Z‐L ‐lysine) then used in situ as a macroinitiator for the polymerization of ε‐caprolactone in the presence of stannous octoate as a catalyst. The triblock copolymers poly(ethylene glycol) monomethyl ether –block‐poly(Z‐L ‐lysine)‐block‐poly(ε‐caprolactone) (MPEO‐PzLLys‐PCL) were synthesized via the click reaction of the propargyl‐terminated PzLLys‐PCL and azido‐terminated poly(ethylene glycol) monomethyl ether (PEO‐N₃) in the presence of CuBr and 1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) catalyst system. After the removal of Z groups of L ‐lysine units, amphiphilic and biocompatible ABC triblock copolymers MPEO‐PLLys‐PCL were obtained. The structural characteristics of these ABC triblock copolymers and corresponding precursors were characterized by NMR, IR, and GPC. These results showed the click reaction was highly effective. Therefore, a facile approach is offered to synthesize amphiphilic and biocompatible ABC triblock copolymers consisting of polyether, polypeptide and polyester. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis of water-soluble ABC triblock copolymers containing polypeptide segments

This article describes a facile approach for the synthesis of water-soluble ABC triblock copolymers through a combination of atom transfer radical polymerization (ATRP) and click reactions. The bromine-terminated MPEO–PtBA–Br precursor was first prepared by ATRP, and converted into the azido-terminated precursor MPEO–PtBA–N₃ by a simple nucleophilic substitution. Then, MPEO–PtBA–PzLLys triblock copolymers were synthesized via the click reaction of MPEO–PtBA–N₃ and the propargyl-terminated poly(N^ε-carbobenzoxy-l-lysine)s (PzLLys). The water-soluble MPEO–PAA–PLLys ABC triblock copolymers were obtained from the hydrolysis process. The structures of these block copolymers were characterized by NMR, IR and GPC.     

Phase diagrams of ABC linear triblock copolymers under nanopore confinements

The phase diagrams of triblock copolymers in cylindrical nanopores are investigated using the real-space self-consistent field theory in a two-dimensional space. We concentrate on pores with neutral surfaces and invariable diameters, whose rich variety of phases are considered to originate from pure geometric frustration. A series of triangular phase diagrams are constructed by varying the volume fractions for several sets of interaction parameters. These diagrams are sorted into three categories according to their interaction parameters. The confined phase diagrams exhibit several characteristic features that differ from those observed in the bulk. First, a rich variety of geometric frustration phases with strong symmetries, such as cylindrical and square, are observed in the triangular phase space because of the symmetry constraint in the geometric boundary. Second, the frustrated phases present some novel and complex features compared with those in the bulk, demonstrating that the confined morphologies much more sensitively depend on the subtle variation in the binary interaction parameters than those in the bulk. Meanwhile, the entropic energies of the symmetric melts with equal end block volume fractions are investigated to further understand the geometric frustration phase behaviors in the triangular phase diagrams. The reasonable formation mechanisms of the frustration phases are also discussed.     

Influence of the block sequence on the morphological behavior of ABC triblock copolymers

Two series of linear SBV and BSV triblock copolymers have been prepared where S is polystyrene, B is polybutadiene and V is poly(2-vinylpyridine). While the ratio between the weight fractions of S and B was kept constant, the weight fraction of V was varied within each series. Morphological characterization was carried out by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). While BSV triblock copolymers show lamellar morphologies independent of the V content, the SBV triblock copolymers show different core-shell morphologies and a lamellar morphology as a function of the V content.     

Amphiphilic diblock and ABC triblock methacrylate copolymers: synthesis and aqueous solution characterization

Three isomeric, linear, equimolar, amphiphilic ABC triblock copolymers comprising methyl methacrylate (MMA, nonionic hydrophobic), 2-(dimethylamino)ethyl methacrylate, (DMAEMA, ionizable hydrophilic) and hexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) units (10 units in each block) were synthesized by group transfer polymerization (GTP). These were the three block sequence isomers, ABC, ACB and BAC. The corresponding random terpolymer was also prepared. The molecular weights and compositions of all the polymers were characterized by GPC and ¹H NMR. Measurements of the hydrodynamic diameters and cloud points of the copolymers in aqueous solution suggest that the various distributions of monomer units in the four terpolymers (the three triblocks and the random) result in different supramolecular structures with different colloidal stabilities.     

Living anionic polymerization of 4‐diphenylphosphino styrene for ABC triblock copolymers

Living anionic polymerization of 4‐diphenylphosphino styrene (DPPS ) achieved unprecedented poly(S‐b ‐I‐b ‐DPPS ) ABC triblock copolymers with predictable molecular weights and narrow polydispersities. In situ Fourier transform infrared spectroscopy probed the anionic polymerization, monitoring vinyl disappearance during sequential monomer addition for kinetic analysis. Varying the concentration of reinforcing, polystyrenic external blocks enabled diverse compositions with tunable thermomechanical properties and tailored morphology. Dynamic mechanical analysis confirmed the presence of microphase separation in the triblock copolymers and revealed a broad temperature range (ca 100 ^oC ) for a plateau region and onset of flow temperatures above 100 ^oC . Small‐angle X‐ray scattering and atomic force microscopy collectively revealed solid state morphologies of the triblock copolymers and probed phase separation at the nanoscale. Well‐defined poly(S‐b ‐I‐b ‐DPPS ) ABC triblock copolymers with tunable structure ? property relationships now permit phosphorus‐containing thermoplastic elastomers for emerging applications. © 2016 Society of Chemical Industry     

A computer simulation study of the low-angle x-ray scattering obtained from triblock copolymers

Computer programs were developed to produce graphic plots which simulate the lowangle x-ray scattering curves obtained from cast films of triblock copolymers. Models were developed to take account of lattice paracrystallinity, a distribution in size of the scattering elements, various types of lattice packing, and the possibility of more than one type of lattice packing in a loosely bound paracrystal. These studies provide an insight into the possible structure of the macrolattices which have been observed with triblock copolymers.     

ABA triblock copolymers with two crystallizable blocks

Triblock copolymers of the ABA type were synthesized in which the A block is poly(ethylene oxide) (PEO), having molecular weight of 1000 or 2000, and the B block is poly(dimethylsiloxane) (PDMS), having molecular weight of about 8000 or 10,000. When the triblock copolymer was cooled from the melt, the PEO block crystallized at around room temperature. Upon further cooling to liquid nitrogen temperature and reheating, the crystallization of the PDMS middle block took place at around ?90°C. The melting temperatures and degrees of crystallinity of the PEO blocks in the copolymers were depressed from their respective pure state values. On the other hand, the melting points of the PDMS middle blocks in the copolymers were the same as the pure state values; furthermore, the degrees of crystallinity were unexpectedly much higher. © 1993 John Wiley & Sons, Inc.     

Synthesis of amphiphilic rod-coil ABC triblock copolymers with oligo(para-phenyleneethynylene) as the middle rigid block

An amphiphilic rod-coil ABC triblock copolymers using rigid oligo(para-phenyleneethynylene) (OPE) as the middle rod segment, poly(ethylene oxide)-block-oligo(para-phenyleneethynylene)-block-polystyrene (PEO-b-OPE-b-PS), was designed and successfully synthesized. In the synthetic route, a kind of macroinitiator, PEO-b-OPE-Br was achieved by stepwise coupling of iodo-terminated poly(ethylene oxide) and oligo(para-phenyleneethynylene) with amino end group, capping with 2-bromopropionyl bromide. Subsequently, from this macroinitiator atom transfer radical polymerization (ATRP) of styrene was performed to obtain PEO-b-OPE-b-PS. The resulting copolymers were characterized by nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). All these novel copolymers were affirmed to have well-defined structures and narrow molecular weight distributions.     

Blends of syndiotactic polystyrene with SEBS triblock copolymers

Blending of styrene-b-(ethylene-co-1-butene)-b-styrene (SEBS) triblock copolymers with syndiotactic polystyrene (PSsyn) has been performed in a Brabender mixer above the higher glass transition temperature of the triblock copolymer but below the PSsyn melting point. The large excess of the triblock copolymer over the homopolymer as well as the significant amount of plasticized amorphous PSsyn phase allowed the easy processing under the used temperature conditions with good interface compatibility. The consequent interfacial adhesion between the amorphous PS phase and the unmelted PSsyn crystallites affects both the final morphology of the blend as well as its dynamic behavior. Indeed, such solid particles act as reinforcing point of the overall blend structure, as evidenced by scanning electron microscopy. Moreover, they contribute to a T_g increase in the order of 20 °C with respect to pure SEBS and to an appreciable conservation of mechanical properties at temperatures higher than the T_g of the PS blocks of SEBS. The mechanical and thermal behavior of the synthesized blends has been studied and tentatively correlated to the molecular weight ratio between PSsyn and the PS blocks of SEBS.     

Crystallization assisted self-assembly of semicrystalline block copolymers

The self-assembly of block copolymers (BCPs) in the presence of crystallization as the second driving force is reviewed, for BCPs in the bulk, thin films, single crystals and micelles. The crystallization of semicrystalline BCPs in the bulk is introduced briefly and the unique morphologies of semicrystalline BCPs at various levels due to crystallization are discussed. The thin film morphologies shown by crystalline BCPs are summarized in terms of the factors affecting the relative strengths of various driving forces. Special attention is paid to the thin film morphologies of functional BCPs containing crystalline poly(3-alkylthiophene) and perylene bisimide units. The single crystal morphologies of semicrystalline BCPs are also presented. Finally, the micellar morphologies of BCPs with a semicrystalline core are reviewed. The controlled and living growth of crystalline micelles, which is the unique characteristic of such micelle, is then discussed.     

Self-assembly of ABC coil-rod-coil triblock molecules with perforated lamellar mesophases

The synthesis and characterization of ABC coil-rod-coil triblock (monomer) and ABCBA coil-rod-coil-rod-coil triblock dimer (dimer) molecules of docosyl 4′-[4′-[methyloxypoly(ethyleneoxy)ethyloxy]-4-biphenylcarboxyloxy]-4-biphenyl carboxylate with poly(ethylene oxide) (PEO) coil are described. The self-assembling behavior of triblock molecules is characterized by a combination of techniques consisting of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM), and X-ray diffraction (XRD) measurement. Monomer and dimer self-assemble into three lamellar crystalline phases (k₁, k₂, and k₃) and 3D-hexagonally perforated lamellar (HPL) and 2D-hexagonal columnar (col) liquid crystalline phases as temperature increases. In addition to the phases exhibited by monomer, dimer shows 3D-tetragonally perforated lamellar (TPL) and spherical micellar (M) liquid crystalline phases. These results demonstrate that simple dimerization of coil-rod-coil molecule by connecting PEO block induces 3D-tetragonally perforated lamellar and spherical micellar mesophases.     

Ultrasonic studies of styrene-butadiene-styrene triblock copolymers

Ultrasonic measurements covering the frequency range 5–1000 MHz are reported on solid styrene-butadiene-styrene triblock copolymers and their solutions in toluene and cyclohexane. In the solid, two distinct relaxation processes were observed, corresponding to the glass transitions of the polystyrene and polybutadiene phases. Two distinct processes were observed also in the swollen solid, the relaxation peaks being shifted to lower temperatures with plasticization of the polymer by the solvent. Comparison of the changes observed with those detected in a similar mixture of the corresponding homopolymers confirms the importance of phase separation in the swollen copolymer. An increase in the high frequency attenuation of semi-dilute solutions can be associated with scattering of the sound wave by micelle structures. The temperature-concentration locus at which this scattering is first observed correlates with other observations of microphase separation in triblock copolymers. At these concentrations, the low frequency relaxation curves deviate from extrapolation from dilute solutions data indicative of significant polymer-polymer entanglement interaction.     

Structure and thermal behavior of nylon‐6/polytetrahydrofuran triblock copolymers obtained via anionic polymerization

The structure, crystallization, and phase behavior of nylon6‐b‐polytetrahydrofuran‐b‐nylon6 triblock copolymers synthesized via activated anionic polymerization have been studied. The composition, molecular weight of polytetrahydrofuran (PTHF) soft block, and type of polymeric activators (PACs) have been varied. Differential Scanning Calorimetry (DSC), Wide‐Angle X‐ray Diffraction (WAXD), Transmission Electron Microscopy (TEM), and Polarized Light Microscopy (PLM) experiments have revealed that in triblock copolymers only the nylon‐6 component crystallizes while PTHF segments are amorphous. The soft blocks do not alter the spherulitic crystalline structure of nylon‐6 and hard blocks crystallize in the α‐modification. The degree of crystallinity decreases with increasing PTHF concentration. The phase behavior has been investigated by Dynamic Mechanical Thermal Analysis (DMTA). Two different glass transition temperatures (T_g) for all samples have been observed. This indicates that nylon‐6 and PTHF segments are not molecularly miscible and the copolymers are microphase separated. The mechanical properties of the copolymers synthesized have been evaluated. Nylon‐6 copolymers with soft block concentrations up to 10 w/w %, exhibit improved notched impact strength in comparison to the nylon‐6 homopolymer, retaining relatively high hardness and tensile strength. All copolymers possess low water absorption and good thermal stability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1448–1456, 2002; DOI 10.1002/app.10448     

High molecular weight diblock and ABA/ABC triblock copolymers of tert‐butyl (meth)acrylate

AB diblock copolymers were prepared by use of poly(tert‐butyl (meth)acrylate) (PtBA/PtBMA) as monofunctional macroinitiator in atom transfer radical polymerization of various (meth)acrylates (methyl, butyl) in the presence of the CuBr/N, N, N′, N′, N″‐pentamethyldiethylenetriamine catalyst system. Then using the diblock copolymer as macroinitiator with a bromine atom at the chain end, ABC and ABA triblock copolymers containing at least one PtBA or PtBMA segment were synthesized via polymerization of the selected (meth)acrylic monomer. Gel permeation chromatography was applied to determine molecular weights and polydispersity indices. The latter, for block copolymers prepared without deactivator addition, were in the range 1.2‐1.6 with a high degree of polymerization (150‐500). The chemical compositions of the block copolymers were characterized with ¹H nuclear magnetic resonance. The kind of combined segments and their lengths influenced the glass transition temperature (T_g) determined by differential scanning calorimetry. Copyright © 2012 Society of Chemical Industry     

紫杉醇-SIBS体外药物释放动力学研究

采用聚（苯乙烯-b-异丁烯-b－苯乙烯）三嵌段共聚物（SIPS）作为紫杉醇药物载体,研究了紫杉醇释放动力学行为。对紫杉醇-SILKS载药共聚物进行了差示量热扫描仪分析（DSC）和原子力显微镜（AFM）的表征;研究了不同苯乙烯（St）含量的紫杉醇-SIBS载药共聚物在pH=7．4磷酸缓冲液（PBS）（37℃）中的动力学。结果表明紫杉醇-SIRS载药共聚物随着St含量的增加,紫杉醇的释放率较低,且其释药率在8d以后趋于平稳;在体外释药过程中随着磷酸缓冲液的置换量越大,紫杉醇的释放率越高。     

Synthesis and characterization of polyoxazoline-polysulfone triblock copolymers

Amphiphilic triblock poly(2-ethyl-2-oxazoline-b-sulfone-b-2-ethyl-2-oxazoline) (PEOX-b-PSF-b-PEOX) and poly(2-ethyl-2-oxazoline-co-ethyleneimine-b-sulfone-b-2-ethyl-2-oxazoline-co-ethyleneimine) (PEOXcoPEI-b-PSF-b-PEOXcoPEI) copolymers were synthesized for potential use as water purification membranes. Poly(arylene ether sulfone) (polysulfone) oligomers of controlled molecular weight were prepared by nucleophilic step polymerization of 4,4′-dichlorodiphenyl sulfone with a molar excess of bisphenol-A. The phenolate endgroups were then reacted with ethylene carbonate to afford telechelic aliphatic hydroxyethyl groups. These were tosylated to produce macroinitiators for ring-opening cationic polymerization of 2-ethyl-2-oxazoline. Subsequently, the pendent amides on the hydrophilic PEOX blocks were also hydrolyzed to generate positively charged PEOXcoPEI-b-PSF-b-PEOXcoPEI copolymers. Compositions with high polysulfone compositions relative to the hydrophilic blocks were of particular interest because they maintained good mechanical integrity in water. Water uptake at room temperature increased up to 18 wt% for copolymers with 22 wt% of the hydrophilic components. Solid-state thermal properties suggested some phase mixing of the components in the PEOX-b-PSF-b-PEOX copolymers but better phase separation of the blocks in the partially hydrolyzed PEOXcoPEO-b-PSF-b-PEOXcoPEI materials.     

Synthesis and characterization of nylon-polyisobutylenenylon triblock copolymers

Nylon-6-polyisobutylene-nylon-6 triblock copolymers have been synthesized by converting telechelic polyisobutylene diols to , -diisocyanate polyisobutylenes and using these macroactivators, in conjunction with strong base, to induce the subsequent anionic polymerization of -caprolactam. Pure block copolymer was obtained by suitable sequential extraction. Products were characterized by composition, molecular weight and DSC.     

Orientation of triblock copolymers in planar extension

Three commercial styrenic triblock copolymers were subjected to planar extension in a lubricated channel die, as a model for the orientation that may occur during processing operations. Materials that contain cylinders of polystyrene show a pronounced orientation of the cylinder axis in the flow direction, as revealed by small-angle X-ray scattering in the three orthogonal directions. This anisotropy produces small-strain tensile moduli that differ by a factor of 10 or more in the two in-plane directions. A material that contains lamellae of polystyrene shows pronounced orientation of the lamellae in the plane of the sample; in particular, lamellar normals are strongly forbidden from pointing along the flow direction. For similar strains, planar extension is much more effective in orienting these materials than simple shear.