侧基带有L-苯丙氨酸的手性两亲嵌段共聚物的合成及其自组装行为

N3-苯丙氨酸与嵌段共聚物聚乙二醇-b-聚炔丙基缩水甘油(MPEO-b-PGPE)发生click反应,合成了具有光学活性的两亲嵌段共聚物聚乙二醇-B-聚L-苯丙氨酸三唑基缩水甘油(MPEO-b-PGTP),用1H-NMR和元素分析对其结构和组成进行表征.并对其自组装行为进行研究,滴体积法测定MPEO-b-PGTP溶...     

Supramolecular self-assembly of conjugated diblock copolymers

This paper describes the synthesis and characterization of a novel series of copolymers with different lengths of oligo(phenylene vinylene) (OPV) as the rod block, and poly(propylene oxide) as the coil block. Detailed characterization by means of transmission electron microscopy (TEM), atomic force microscopy (AFM), and small-angle neutron scattering (SANS) revealed the strong tendency of these copolymers to self-assemble into cylindrical micelles in solution and as-casted films on a nanometer scale. These micelles have a cylindrical OPV core surrounded by a poly(propylene glycol) (PPG) corona and readily align with each other to form parallel packed structures when mica is used as the substrate. A packing model has been proposed for these cylindrical micelles.     

具有特殊相互作用的聚合物共混物在选择性溶剂中的自组装行为

研究了磺化聚苯乙烯(SPS)/聚4-乙烯基吡啶(P4VP)在选择性溶剂甲醇中的自组装行为。用动态光散射的方法考察了P4VP/甲醇初始浓度以及Cu^2^+的加入对溶液中粒子尺寸的影响,并研究了Cu^2^+的加入对聚合物溶液粘度的影响。     

Synthesis of pH-responsive amphiphilic diblock copolymers containing polyisobutylene via oxyanion-initiated polymerization and their multiple self-assembly morphologies

 Two pH-responsive amphiphilic diblock copolymers, namely polyisobutylene-block-poly[2-(N,N-dimethylamino)ethyl methacrylate] (PIB-b-PDMAEMA) and polyisobutylene-block-poly(metharylic acid) (PIB-b-PMAA), were synthesized via oxyanion-initiated polymerization, and their multiple self-assembly behaviors have been studied. An exo-olefin-terminated highly reactive polyisobutylene (HRPIB) was first changed to hydroxyl-terminated PIB (PIB-OH) via hydroboration-oxidation of C＝C double bond in the chain end, and then reacted with KH to yield a potassium alcoholate of PIB (PIB-O^-K⁺). PIB-O^-K⁺ was immediately used as a macroinitiator to polymerize DMAEMA monomer, resulting in a cationic diblock copolymer PIB-b-PDMAEMA. With the similar synthesis procedure, the anionic diblock copolymer PIB-b-PMAA could be prepared via a combination of oxyanion-initiated polymerization of tert-butyl methacrylate (tBMA) and subsequent hydrolysis of tert-butyl ester groups in PtBMA block. The functional PIB and block copolymers have been fully characterized by ¹H-NMR, FT-IR spectroscopy, and gel permeation chromatography (GPC). These samples allowed us to systematically investigate the effects of block composition on the pH responsivity and various self-assembled morphologies of the copolymers in THF/water mixed solvent. Transmission electron microscopy (TEM) images revealed that these diblock copolymers containing small amount of original PIB without exo-olefin-terminated group are able to self-assemble into micelles, vesicles with different particle sizes and cylindrical aggregates, depending on various factors including block copolymer composition, solvent polarity and pH value.     

Polymerization-induced self-assembly of metallo-polyelectrolyte block copolymers

Cobaltocenium-containing polyelectrolyte block copolymer nanoparticles were prepared via polymerization-induced self-assembly (PISA) using aqueous dispersion RAFT polymerization. The cationic steric stabilizer was a macromolecular chain-transfer agent (macro-CTA) based on poly(2-cobaltocenium amidoethyl methacrylate chloride) (PCoAEMACl), and the core-forming block was poly(2-hydroxypropyl methacrylate) (PHPMA). Stable cationic spherical nanoparticles were formed in aqueous solution with low dispersity without adding any salts. The chain extension of macro-CTA with HPMA was efficient and fast. The effects of block copolymer compositions, solid content, charge density, and addition of salts were studied. It was found that the degree of polymerization of both the stabilizer PCoAEMACl and the core-forming PHPMA had a strong influence on the size of nanoparticles. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 77–83     

Morphologies of microphase-separated conformationally asymmetric diblock copolymers

The equilibrium morphological behavior of a series of conformationally asymmetric linear diblock copolymers is characterized via small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The linear diblock molecules of polyisoprene and poly(t-butylmethacrylate) (PtBMA) are prepared anionically over a range of PtBMA volume fractions 0.17 to 0.85. Solution light-scattering experiments are performed on PtBMA homopolymer at theta conditions, and the results were compared with PI data in the literature in order to characterize the degree of conformational asymmetry between the respective blocks. This conformational asymmetry is quantified by an ε of 0.75. The experimental results are compared with morphological behavior calculated utilizing self-consistent mean field theory for a diblock system with ε = 0.75. At middle to high PtBMA volume fractions, ϕ_PtBMA > 0.30, the experimental morphological behavior agrees well with the calculated behavior; the microphase boundaries are slightly shifted to higher volume fractions of the PtBMA block due to its larger Kuhn length. At ϕ_PtBMA < 0.30, however, discrepancies are found in the volume fraction dependence of experimentally determined morphological behavior and that calculated theoretically. Interestingly, extremely well-ordered cylindrical microstructures were observed for PI cylinder domains embedded in PtBMA matrices; these samples were prepared by solvent casting with no treatment, such as shearing, to enhance long-range order. These well-ordered cylinder structures contrast with PtBMA cylinders in a PI matrix on the opposite side of the phase diagram that have very poor long-range order. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2629–2643, 1997     

Synthesis and characterization of amphiphilic antibacterial copolymers

Macromolecule antimicrobials have been explored in foundational research and practical application due to their potential merit for reducing the residual toxicity, increasing their efficiency, selectivity, and prolonging the lifetime of the antimicrobial material. In this work, the quaternized poly(styrene)‐b‐poly(DMAEMA) diblock polymers are synthesized by reversible addition‐fragmentation chain transfer polymerization (RAFT). The minimum inhibitory concentration (MIC) evaluation and optical density (OD) method demonstrated that the amphiphilic antibacterial biomaterials have exceptional antibacterial properties. The amphiphilic polycation has an admirable antibacterial property, and these quaternized diblocks are potent biocides and nonhemolytic. The relationship between the structure and activity is discussed with respect to molecular weight of the diblocks and bacteria structural dependence. Copyright © 2011 John Wiley & Sons, Ltd.     

Zinc ion induced polymorphism in macromolecular self-assembly of diblock copolymers

A novel interconnected cylindrical micellar network was prepared from a diblock copolymer, poly(maleic anhydride-alt-styrene)-b-polystyrene, in ethanol under a self-assembly directing agent: Zn²⁺ ions. The solution containing interconnected cylindrical network is bluish and transparent, which is stable for more than 6 months at room conditions without any observable macroscopic phase separation. In aqueous solution, however, hydrolysis of the anhydride yields hydrophilic carboxyl groups, which result in formation of uniform positive spherical micelles from the same diblock polymer. The nanostructures of both the spherical micelles and cylindrical assemblies are characterized with light scattering and transmission electron microscopy (TEM).     

Organized polymerization of functional diblock copolymers possessing central isoprene groups

Functional diblock copolymers possessing central isoprene groups were synthesized by anionic addition in a three-stage process using styrene, isoprene, and 2-vinylpyridine monomers. These diblock copolymers formed microphase-separated structure in the solid state. Where the central isoprene groups are organized regularly at the domain interface of the microphase-separated structure, this is due to the functional groups being located at the block junction position. Addition-condensation of diblock copolymer film with sulfur monochloride formed A_nB_n star block copolymers by organization effects. © 1993 John Wiley & Sons, Inc.     

Biodegradable anastomotic tube prepared from diblock copolymers of mPEG-b-PLA and mPEG-b-PLGA

During the healing and reconstruction process of digestive tract, biodegradable anastomat plays an important role. Various of materials have been explored to prepare suitable anastomat. However, the biodegradable ratio or biocompatibility could not meet the requirement of wound healing in clinical application. To overcome these obstacles, we synthetized methoxy-poly(ethylene glycol)-block-polylactide (mPEG-b-PLA) and methoxy-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (mPEG-b-PLGA) with different molecular weight. Biodegradable anastomotic tubes were prepared from these diblock copolymers using electrospinning technique. The thickness of anastomotic tube could be regulated by spinning conditions. Anastomotic tubes had exhibited excellent hemocompatibility (hemolysis ratios were ranged from 0.5% to 1.5%) and cytocompatibility. After 3?days, epithelial cells were adhered closely and covered fully on the surface of nanofibrous tubes. Moreover, mPEG-b-PLGA₃ based anastomotic tube had play an important role to improve the healing and reconstruction process of cecal incision. The biodegradable anastomotic tubes from diblock copolymers of mPEG-b-PLA and mPEG-b-PLGA could promote healing and reconstruction of digestive tract and might play an important role after operation.     

Controlling interfacial interactions for directed self assembly of block copolymers

Over the past 15 years, block copolymer lithography has emerged as its own research field within the broader block copolymer and polymer thin film communities. This distinction is associated with the unique requirements set by the semiconductor device industry, such as low-defect densities, precise feature registration, and complex pattern layouts. To achieve perfection in block copolymer lithography, the surface and substrate interactions must be carefully tuned to control domain ordering in three dimensions. This perspective discusses recent modeling efforts that underline the challenges of predicting interfacial interactions and the resulting block copolymer structures. We emphasize studies that facilitate the design and interpretation of experiments, including materials selection, guiding pattern geometry, and selecting tools for three-dimensional metrology. Finally, we propose that translation of block copolymer lithography to semiconductor manufacturing will require integrated experimental and modeling efforts to interrogate the vast parameter space that controls both lateral and out-of-plane ordering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 96–102     

Fluorinated AB diblock copolymers and their aggregates in organic solvents

This investigation reported the preparation of fluorinated and nonamphiphilic well‐defined poly(styrene)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PS‐b‐PHFBMA) diblock copolymers via atom transfer radical polymerization (ATRP). Their chemical composition, structure, and bulk morphology were thoroughly investigated. In addition, their self‐assembly behavior in a dilute organic mixture solution was investigated. It was found that that the ATRP could be used to prepare the well‐defined fluorinated and nonamphiphilic PS‐b‐PHFBMA diblock copolymers in a controlled manner. The results also showed that abundant morphologies including sphere, worm‐like structure, and vesicle could be formed with different volume ratios of these two solvents, which proves that the nonamphiphilic fluorinated diblock copolymers can self‐assemble in a dilute solution, and the aforementioned reason for self‐assembly was also discussed preliminarily in this work. Finally, the effect of temperature on the aggregates was investigated to verify whether the self‐assembly behavior was to some extent temperature sensitive. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Aggregation behavior of MPEG‐PCL diblock copolymers in aqueous solutions and morphologies of the aggregates

Poly(ethylene glycol)‐b‐polycaprolactone (MPEG‐PCL) diblock copolymers were synthesized via a ring‐opening polymerization of ε‐CL monomers with MPEG as an initiator. Their solubilities and apparent critical micelle concentrations (CMC) in aqueous solution were investigated as well as the determination of the micellar hydrodynamic diameter using dynamic light scattering (DLS). As PCL block length increased, the solubility and CMC decreased while diameters of micelles increased. The gel–sol transition behaviors were investigated using a vial tilting method. Aqueous solutions of copolymers undergo a gel to sol transition with increase in temperature when their polymer concentrations are above a critical gel concentration (CGC). The CGC of the copolymers and gel–sol transition temperature are influenced by the PCL chain length. The tapping mode AFM was performed by imaging the freeze‐dried deposits from the copolymer solutions on mica to investigate a process from free chains to micelles and to gel. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3406–3417, 2006     

Self-assembly mechanism of PEG-b-PCL and PEG-b-PBO-b-PCL amphiphilic copolymer micelles in aqueous solution from coarse grain modeling

We followed the self-assembly of high-molecular weight MePEG- b -PCL (poly(methyl ethylene glycol)-block-poly(ε-caprolactone)) diblock and MePEG- b -PBO- b -PCL (poly(methyl ethylene glycol)-block-poly(1,2-butylene oxide)-block-poly(ε-caprolactone)) into micelles using molecular dynamics simulation with a coarse grain (CG) force field based on quantum mechanics (CGq FF). The triblock polymer included a short poly(1,2-butylene oxide) (PBO) at the hydrophilic-hydrophobic interface of these systems. Keeping the hydrophilic length fixed (MePEG₄₅), we considered 250 chains in which the hydrophobic length changed from PCL₄₄ or PBO₆- b -PCL₄₃ to PCL₆₂ or PBO₉- b -PCL₆₁. The polymers were solvated in explicit water for 2 μs of simulations at 310.15 K. We found that the longer diblock system undergoes a morphological transition from an intermediate rod-like micelle to a prolate-sphere, while the micelle formed from the longer triblock system is a stable rod-like micelle. The two shorter diblock and triblock systems show similar self-assembly processes, both resulting in slightly prolate-spheres. The dynamics of the self-assembly is quantified in terms of chain radius of gyration, shape anisotropy, and hydration of the micelle cores. The final micelle structures are analyzed in terms of the local density components. We conclude that the CG model accurately describes the molecular mechanisms of self-assembly and the equilibrium micellar structures of hydrophilic and hydrophobic chains, including the quantity of solvent trapped inside the micellar core.     

Aggregation behavior of cyclic rod-coil diblock copolymers in selective solvents

The aggregation behavior of cyclic rod-coil (RC) diblock copolymers in dilute solutions is investigated through dissipative particle dynamics simulation. By varying the rod length and coil length, cyclic RC copolymers in selective solvents exhibit various morphologies, including spherical micelle, vesicle, bilayer disc, and ribbon bundle structure. Compared with the equivalent linear RC copolymer, only spherical micelle and barrel bundle phase are observed. Rod length is the major factor that controls the liquid-crystalline behavior of RC copolymer systems, while the coil length has a secondary effect on the aggregate morphology. The size of rod bundle varies with the coil length, especially for the end-toend ribbon bundle and side-by-side barrel bundle, which are assembled by cyclic and linear RC copolymer solutions. This finding indicates that the ribbon bundle or nanofiber-like structure in cyclic RC copolymers can be obtained by controlling the rod length and coil length, and thus the optical and electrical properties of RC copolymer would be further controlled and optimized. Results illustrate that cyclization of a linear RC copolymer induces remarkable differences in the rod arrangement and aggregation behavior, thereby indicating the competition between interfacial energy, rod orientational entropy, coil stretching entropy, and packing constraints.     

Novel organotin-containing diblock copolymer with tunable nanostructures: Synthesis, self-assembly and morphological change

Interesting self-assembly behavior and morphological change of a novel organotin-containing diblock copolymer were firstly reported. The organotin-containing diblock copolymer, poly(methyl methacrylate)-block-poly(acetoxydibutyltin methacrylate) (PMMA-b-PADBTMA), was prepared via RAFT polymerization of ADBTMA with PMMA as the macroCTA and AIBN as the initiator in toluene. Both the FT-IR and TG analysis revealed an incorporation of both co-monomers in the resulted polymer backbone. The ratio of two segments was determined indirectly by TG analysis, gravimetric method and derivative process. All results from the different methods were well matched. And it was found that the morphology of the diblock copolymer could be changed easily from vesicles to nano-particle or cross-linked nano-composite under the ultrasonication or additional Ph₂SnCl₂, respectively. All the morphologies were analyzed by SEM, TEM and DLS. The self-assembly and the morphological change attributed to the strong coordination action between tin atoms and the carbonyl groups among PADBTMA segments.     

Self-assembly of monodisperse polymer microspheres from PPQ-b-PEG rod-coil block copolymers inselective solvents

Self-assembly of macromolecules is a new fastdeveloping research field in recent years. So far it hasbeen known that many different forms and orderedfunctional nanometer materials, nanometer structurematerials and ordered porous materials are obtained bys…     

pH/enzyme/light triple-responsive vesicles from lysine-based amphiphilic diblock copolymers

We report the synthesis of pH- and enzyme-responsive amphiphilic diblock copolymers through reversible addition-fragmentation chain transfer polymerization of a lysine-derived methacrylate monomer comprising p-nitrobenzyl carbamate (pNBC) functionality using a poly(ethylene glycol)-modified macro-chain transfer agent. Depending on the hydrophobic block length, the diblock copolymers self-assemble to form spherical micelles, wormlike micelles, and bilayered vesicles in the aqueous solution. The responsive behaviors of the polymeric vesicles to pH, enzyme, and light are investigated in detail. As the pH lowers to pH 5.0, the polymeric vesicles undergo a morphological transition from vesicles to spherical micelles. In the presence of nitroreductase and a cofactor NADH, the decomposition of pNBC releases the ε-NH₂ of the lysine moiety and hence induces the generation of the vesicles with crosslinked membranes at pH 7.4. Moreover, owing to the degradation of pNBC moiety under UV irradiation, the polymeric vesicles also demonstrate a photo-responsive feature. As the irradiation time prolongs, it is observed a light-triggered morphological transition from vesicles to wormlike micelles with network-like structures.