Controlled processing of polymer nanoribbons: Enabling microhelix transformations

Flow‐coated, two‐dimensional polymer ribbon structures undergo a shape‐transformation into a three‐dimensional helix upon their release into a solution. Driven by surface forces and due to geometric asymmetry, the helix radius and spring constant depend upon the ribbon cross‐section dimensions, surface energy, and material elastic modulus. Such spring‐like microhelices offer multiple functionalities combined with mechanical stretching and shape recovery. Fabricating such microhelices requires a sequence of processing steps, beginning with flow‐coating of ribbons on a substrate, followed by etching of a “scum layer” to allow for an independent release into a solution, upon which shape‐transformation occurs. During the deposition‐etch‐release sequence, various control parameters influence the nanoribbon size and geometry, hence the helix properties. The experimental study presented here focuses on the influence of meniscus height, substrate velocity, substrate surface energy, and etch time on nanoribbon size (height and width), scum layer thickness, and helix radius. The results show that meniscus height and contact angle dictate flux toward the meniscus edge and volume available for spatial assembly, allowing control over the aspect ratio of ribbons. We vary the aspect ratio by two orders of magnitude, while maintaining geometric asymmetry needed for helix shape‐transformation. We provide robust scaling for the nanoribbon size and geometry and report the advantages and disadvantages of different parameters, in the control of polymer nanoribbon and helix fabrication. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1270–1278     

聚合物纳米杂化材料的控制合成、自组装及功能化

聚合物纳米杂化材料的制备及功能化是当前国际前沿研究课题之一.特殊结构的聚合物可以通过分子间特殊相互作用,在纳米尺度上自发地组装成具有特殊结构和形态的集合体,这类材料在新材料、电子以及生物医学等领域具有广泛的应用前景.本文介绍国内外,特别是厦门大学在双亲性分子及嵌段共聚物的模板自组装、基于POSS单体纳米构筑单元以及POSS嵌段聚合物自组装的有机/无机纳米杂化材料、模板控制导电高分子材料纳米形态构筑等领域材料的可控合成和组装,与此同时对相关材料的性能及功能化应用进行了简要的讨论.     

偶氮苯基两亲性聚合物的自组装行为研究进展

偶氮苯基两亲性聚合物结合了偶氮苯基团的光响应、酶响应、主客体识别特性和两亲性聚合物的自组装特性,能够在选择性溶剂中发生聚合物可控自组装行为,这使得其在药物控释、纳米技术和生物医学材料等领域受到了广泛的关注。本文从结构类型和合成方法出发,综述了新型偶氮苯基两亲性聚合物在溶液中的自组装研究进展,并对该领域的发展前景进行了展望。     

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。     

Dynamic self-assembly of nanoparticles using thermotropic liquid crystals

ABSTRACT

3D nanoparticle-based materials with reconfigurable structure have gained vast attention due to the unique possibility of tailoring nanoparticle-related quantum confinement effects. These properties make active nanoparticle assemblies promising candidates for future optoelectronic and metamaterial technologies; however, integration of these materials into real-world applications is still challenging. In this context, the use of stimuli responsive liquid-crystals (LCs) offers a fascinating and industrially feasible strategy for active directing of NPs. Here, we briefly review LCs/NPs hybrid systems in which dynamic behaviour is achieved by affecting either LC matrix or LC ligands. We also experimentally evaluate a complementary strategy based on directly affecting metallic core of LC-covered NPs in an Ostwald ripening process.     

Preparation and self-assembly of amphiphilic polymer with aggregation-induced emission characteristics

An amphiphilic polymer bearing tetraphenylethene (TPE) moiety was synthesized by convenient reactions. The polymer exhibits unique aggregation-induced emission (AIE) characteristics and can self-assemble to size-tunable particles in DMF/water mixtures. The polymer nanoparticles can be used for cell imaging, which provides a potential stable fluorescent tool to monitor the distribution of drugs and bioconjugates in living cells.     

Self-assembly of an alkylated guanosine derivative into ordered supramolecular nanoribbons in solution and on solid surfaces

We report on the synthesis and self-assembly of a guanosine derivative bearing an alkyloxy side group under different environmental conditions. This derivative was found to spontaneously form ordered supramolecular nanoribbons in which the individual nucleobases are interacting through H-bonds. In toluene and chloroform solutions the formation of gel-like liquid-crystalline phases was observed. Sub-molecularly resolved scanning tunneling microscopic imaging of monolayers physisorbed at the graphite-solution interface revealed highly ordered two-dimensional networks. The recorded intramolecular contrast can be ascribed to the electronic properties of the different moieties composing the molecule, as proven by quantum-chemical calculations. This self-assembly behavior is in excellent agreement with that of 5'-O-acylated guanosines, which are also characterized by a self-assembled motif of guanosines that resembles parallel ribbons. Therefore, for guanosine derivatives (without sterically demanding groups on the guanine base) the formation of supramolecular nanoribbons in solution, in the solid state, and on flat surfaces is universal. This result is truly important in view of the electronic properties of these supramolecular anisotropic architectures and thus for potential applications in the fields of nano- and opto-electronics.     

Evaluation of poly([2‐(acryloyloxy)ethyl]trimethylammonium chloride) cationic polymer capillary coating for capillary electrophoresis and electrokinetic chromatography separations

Capillary electrophoresis and electrokinetic chromatography are typically carried out in unmodified fused‐silica capillaries under conditions that result in a strong negative zeta potential at the capillary wall and a robust cathodic electroosmotic flow. Modification of the capillary wall to reverse the zeta potential and mask silanol sites can improve separation performance by reducing or eliminating analyte adsorption, and is essential when conducting electrokinetic chromatography separations with cationic latex nanoparticle pseudo‐stationary phases. Semipermanent modification of the capillary walls by coating with cationic polymers has proven to be facile and effective. In this study, poly([2‐(acryloyloxy)ethyl]trimethylammonium chloride) polymers were synthesized by reversible addition‐fragmentation chain transfer polymerization and used as physically adsorbed semipermanent coatings for capillary electrophoresis and electrokinetic chromatography separations. An initial synthesis of poly([2‐(acryloyloxy)ethyl]trimethylammonium chloride) polymer coating produced strong and stable anodic electroosmotic flow of –5.7 to –5.4 × 10⁻⁴ cm²/V⋅s over the pH range of 4–7. Significant differences in the magnitude of the electroosmotic flow and effectiveness were observed between synthetic batches, however. For electrokinetic chromatography separations, the best performing batches of poly([2‐(acryloyloxy)ethyl]trimethylammonium chloride) polymer performed as well as the commercially available cationic polymer polyethyleneimine, whereas polydiallylammonium chloride and hexadimethrine bromide did not perform well.     

Topological polymer chemistry by programmed self-assembly and effective linking chemistry

Ongoing challenges in topological polymer chemistry are reviewed. In particular, we focus on recent developments in an “electrostatic self-assembly and covalent fixation (ESA–CF)” process in conjunction with effective linking/cleaving chemistry including a metathesis process and an alkyne–azide click reaction. A variety of novel cyclic polymers having specific functional groups and unprecedented multicyclic macromolecular topologies have been realized by combining intriguing synthetic protocols.     

水溶性聚合物和两亲聚合物——10.两亲聚合物PAMC_(16)S的自组装有序膜

用自组装技术在金(纯金和经阳极氧化的金)表面上获得了新型两亲聚合物PAMC_(16)S的有序膜。用接触角测试,XPS谱和电化学分析等方法对自组装膜进行了表征。根据膜表面的润湿性,金表面的自组装膜是疏水的,亲水的磺酸基团连于金表面,而疏水的碳氢链从表面伸展出。XPS实验结果支持金表面上单层膜的疏水结构。聚合物单层膜复盖的金电极起到含有针孔缺陷的阻膈型电极的作用。单层膜在法拉第反应中显示很强的吸附稳定性,说明聚合物LB膜在潜在应用中有其特有的特点。     

Facile and controllable one-step fabrication of molecularly imprinted polymer membrane by magnetic field directed self-assembly for electrochemical sensing of glutathione

Based on magnetic field directed self-assembly (MDSA) of the ternary Fe₃O₄@PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe₃O₄@PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe₃O₄@PANI into the graphene oxide layers via π–π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe₃O₄@PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N–H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe₃O₄@PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L⁻¹ (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples.     

Crystallization-driven self-assembly of semicrystalline block copolymers and end-functionalized polymers: A minireview

Self-assembly has been a powerful method to fabricate the polymer materials with well-defined structures and morphologies. Such assembled materials have shown wide potential applications in many fields such as nanomaterial, nanomedicine, lithography, and microelectronic. Crystallization has been a general behavior of stereoregular polymers. Besides the various noncovalent interactions, crystallization of polymer blocks or end groups can be an efficient way to manipulate the self-assembly pathway and assembled structures of polymers in both solid and solution. Crystallization-driven self-assembly has been widely implemented for the semicrystalline block copolymers (BCPs) and end-functionalized polymers. This minireview briefly presents the recent progresses in the crystallization-driven self-assembly of BCPs and end-functionalized polymers in both solid and solution states. Formation process, mechanism, and hierarchical structure of the crystallization-induced assemblies for BCPs and end-functionalized polymers are highlighted.     

第三次纳米自组装制备大孔主客体催化材料

本文提出了第三次纳米自组装的正向胶束、反向胶束法,并利用其制备了一种大孔主客体催化材料．以二次纳米自组装Al2O3为主体,根据压汞法,正向胶束法制备的催化材料孔容为0．62～0．80cm^3／g、比表面积为123～137mZ／g、平均孔径为20～23．3nm,孔径分布大于30nm范围的可达58．69％,堆积密度为0．43—0．55g／cm^3,活性金属负载量可达36．99％;由氮气吸附法,反向胶柬法制备的催化材料具有0．74cm^3／g的孔容、262m2／g的比表面积、11．8nm的平均孔径．结果显示,活性金属以球形或棒状的结晶态存在于主体表面,其中,正向胶束法中为直径2-3nm的微晶态纳米粒子,反向胶束法中为直径0．1μm、长1-2．5μm的棒状体．采用催化裂化柴油和催化裂化重循环油（1：2,体积比）混合而得油品对FA．Z20进行50h加氢评价实验,其单位体积活性金属的脱硫率、脱氮率、脱芳烃率（四环、五环）分别为参比剂的4．6、2．1和4．7倍,初活性良好,具有较强的抗结焦性能．     

Determination of pepsin by capillary electrophoresis using mixed polymer coated capillary with switchable properties toward protein adsorption/desorption

In this work, a simple online preconcentration method for quantitative detection of pepsin was realized by using the binary mixed polymer brushes coated capillary with switchable properties toward protein adsorption. Firstly, the binary mixed polymer brushes were prepared by grafting poly(2-methyl-2-oxazoline) and poly(4-vinylpyridine) onto the inner wall of the capillary through a polydopamine anchor. Then the coatings were characterized by X-ray photoelectron spectrometer and electroosmotic flow measurement. The results indicated that the composition of coating could be controlled by varying the feed ratio of poly(2-methyl-2-oxazoline) to poly(4-vinylpyridine) and the inner surface charge could be tuned toward the change of pH and ionic strength. The results showed that when the poly(2-methyl-2-oxazoline)/poly(4-vinylpyridine) mass ratio was 80/20, the highest online preconcentration effect was obtained and the sensitivity enhancement factor was 6.3. Moreover, satisfactory sensitivity (limit of detection: 7.5 ng/mL) and good repeatability were obtained with the online preconcentration method. The polymer-coated capillary was still stable for online preconcentration and detection of pepsin after 50 consecutive runs. Last, the proposed method was used successfully to online preconcentrate pepsin in the saliva matrix.     

Kinetic behavior in self-assembly process of associative polymer solutions

Using associative polymers with different micro-block length (N_H), their kinetic behaviors in the self-assembly process have been discussed with steady flow, step shear rate and dynamic light scattering (DLS) experiments. The results showed that the N_H is the most important parameter to affect rheology of associative polymers, and the equilibrium time and viscosity recovery are an obvious difference from seconds to hours after violent pre-shearing. With DLS data, the hydrophobic micro-zone size is always a polydispersion distribution, and gradually concentrated three scales of size, the associative polymers with higher N_H values have a longer time to reach equilibrium state. The kinetic behavior of associative polymers has a greater potential to apply in enhanced oil recovery (EOR) field, we conclude that the polymers with medium associative strength have a smaller shear thinning index and higher viscosity recovery, and may satisfy the polymer flooding requirements of displacement efficiency and injectivity.     

Rapid capillary electrophoretic determination of glutaraldehyde in photographic developers using a cationic polymer coating

A new capillary electrophoretic (CE) method was developed for the rapid and simple determination of glutaraldehyde in photographic developing solutions. The proposed system is based on the selective pre-capillary derivatization of glutaraldehyde with sulfite and CE determination of anionic glutaraldehyde-bisulfite adduct formed. Since the developing solutions contain large amounts of sulfite ions, the only procedure required for derivatization is a dilution of the sample with carrier electrolyte. For separations of sulfite, acetate, glutaraldehyde-bisulfite and hydroquinone sulfonate anions, capillaries coated with poly(diallyldimethylammonium chloride) prior to analysis were used. Separation of four anions was accomplished in less than 3 min in 5 mmol l⁻¹p-hydroxybenzoate-imidazole (p-HB) electrolyte at pH 6.0 using indirect UV detection at 254 nm. The optimal conditions for the derivatization reaction were established by varying concentration of sulfite, pH and reaction time. The recovery tests established for photographic developer samples were within the range 94.0-98.4%.     

Interfacial self-assembly growth of mesoporous polydopamine nanofilms for formaldehyde sensing

Mesoporous polymer nanofilms combine the advantages of the unique structure of mesopores, the quasi-2D configuration of the films, and the inherent properties of polymers, and have become a kind of ideal candidate for the high-performance micro-nano devices due to their highly accessible surface area and exposed active sites. However, the facile preparation of polymer nanofilms with well-defined mesostructures has remained a great challenge due to the lack of synthetic strategies. In this study, we developed a simple soft-template interfacial co-assembly strategy to in-situ construct mesoporous polydopamine nanofilms with uniform thickness (30 nm) and regularly distributed mesopore arrays (average pore size of 12 nm) on surfaces with different types and morphologies. Furthermore, a single-layer mesoporous polymer nanofilm was directly grown on a quartz crystal microbalance substrate and its performance for sensing formaldehyde was studied. The resulted sensor showed excellent sensing response, fast response/recovery dynamics, and great stability, presenting a great promising landscape for trace detection of formaldehyde gas.