Low‐Temperature Synthesis of Thermoresponsive Diblock Copolymer Nano‐Objects via Aqueous Photoinitiated Polymerization‐Induced Self‐Assembly (Photo‐PISA) using Thermoresponsive Macro‐RAFT Agents

Photoinitiated reversible addition‐fragmentation chain transfer (RAFT) dispersion polymerization of 2‐hydroxypropyl methacrylate is conducted in water at low temperature using thermoresponsive copolymers of 2‐(2‐methoxyethoxy) ethyl methacrylate and oligo(ethylene glycol) methacrylate (M_n = 475 g mol⁻¹) as the macro‐RAFT agent. Kinetic studies confirm that quantitative monomer conversion is achieved within 15 min of visible‐light irradiation (405 nm, 0.5 mW cm⁻²), and good control is maintained during the polymerization. The polymerization can be temporally controlled by a simple “ON/OFF” switch of the light source. Finally, thermoresponsive diblock copolymer nano‐objects with a diverse set of complex morphologies (spheres, worms, and vesicles) are prepared using this particular formulation.

     

PEG‐Modified Macroporous Poly(Glycidyl Methacrylate) and Poly(2‐Hydroxyethyl Methacrylate) Microspheres to Reduce Non‐Specific Protein Adsorption

To minimize non‐specific protein adsorption on macroporous poly(glycidyl methacrylate) and poly(2‐hydroxyethyl methacrylate) microspheres containing amino and/or carboxyl groups, the microspheres are coated with α,ω‐bis‐carboxy poly(ethylene glycol) and amino‐terminated poly(ethylene glycol‐co‐propylene glycol) or α‐methoxy‐ω‐amino poly(ethylene glycol). Adsorption of bovine serum albumin (BSA), γ‐globulin, ¹²⁵I‐BSA, pepsin, and chymotrypsin on neat and PEGylated microspheres is determined by UV–VIS spectroscopy of supernatants and eluates or by measurement of radioactivity in an ionization chamber. Neat and PEGylated microspheres adsorb 0.8–70% and 0.02–44% of protein, respectively.

     

Synthesis of Photocrosslinkable and Amine Containing Multifunctional Nanoparticles via Polymerization‐Induced Self‐Assembly

Photo‐crosslinkable and amine‐containing block copolymer nanoparticles are synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization‐induced self‐assembly of a multifunctional core‐forming monomer, 2‐((3‐(4‐(diethylamino)phenyl)acryloyl)oxy)ethyl methacrylate (DEMA), using poly(2‐hydroxypropyl methacrylate) macromolecular chain transfer agent as a steric stabilizer in methanol at 65 °C. By tuning the chain length of PDEMA, a range of nanoparticle morphologies (sphere, worm, and vesicle) can be obtained. Since cinnamate groups can easily undergo a [2 + 2] cycloaddition of the carbon–carbon double bonds upon UV irradiation, the as‐prepared block copolymer nanoparticles are readily stabilized by photo‐crosslinking to produce anisotropic nanoparticles. The crosslinked block copolymer nanoparticles can be used as templates for in situ formation polymer/gold hybrid nanoparticles.

     

Further Studies on the Anionic Copolymerization of Styrene and Glycidyl Methacrylate in Toluene

Sequential anionic copolymerization of styrene and glycidyl methacrylate (GMA) was performed with the protection of argon under normal pressure, where styrene, GMA, toluene, THF, n-butyllithium and a small amount of lithium chloride (LiCl) were used as first monomer, second monomer, solvent, polar reagent, initiator and additive, respectively. Polystyrene-b-poly(glycidyl methacrylate) diblock copolymers (PS-b-PGMA) with well-defined structure and narrow molecular weight distribution were prepared by the copolymerization reaction of poly(styryl)lithium with GMA under certain temperatures. The copolymers were characterized using gel permeation chromatography (GPC), ¹H-NMR, ¹³C-NMR, thin layer chromatography (TLC) and hydrochloric acid-dioxane argentimetric methods. The effects of additives, copolymerization temperature and THF dosage on the copolymerization were studied. No chain transfer reaction of anionic polymerization of styrene in toluene was observed. Slightly broader molecular weight distribution of PS-b-PGMA was observed with the increase the GMA repeat units. Using THF/toluene blend solvent could reduce the polydispersity index (M _w /M _n ) and dissolve the copolymer better than toluene alone. Lower temperature (< -40°C) and LiCl are required to prepare PS-b-PGMA with narrower molecular weight distribution.     

Functionalization of Styrene-Olefin Block Copolymers by Melt Radical Grafting of Glycidyl Methacrylate and Reactive Blending with PET

Blocks copolymers styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) and styrene-b-(ethylene-co-propylene) (SEP, SEPSEP), with different styrene content and number of blocks in the chain, were functionalized with glycidyl methacrylate (GMA) by melt radical grafting. The influence of monomer concentration, radical initiator and copolymer structure on the grafting degree was examined. The grafted copolymers were characterised by DSC and capillary rheometry. Blends of PET with functionalized SEBS and SEPSEP showed a marked improvement of phase morphology and elongation at break when compared to blends with unfunctionalized copolymers.     

Amphiphilic Diblock Copolymer with Dithienylethene Pendants: Synthesis and Photo‐Modulated Self‐Assembly

In this work, an amphiphilic diblock copolymer (PEG₄₃‐b‐PSDTE₂₉) bearing photochromic dithienylethene (DTE) pendants is synthesized by reversible addition fragmentation chain transfer radical polymerization. The diblock copolymer was characterized by spectroscopic methods and gel permeation chromatography. The analyses proved the well‐defined structure and narrow molecular weight distribution of the diblock copolymer. The DTE pendants could undergo reversible photoisomerization between their open and closed forms in solution when irradiated with UV and visible light as indicated by ¹H NMR and UV‐vis spectroscopy. Hollow vesicle‐like structures were formed by gradually adding deionized water to the colorless PEG₄₃‐b‐PSDTE_29open (DTE in open form) tetrahydrofuran solution. Under the same conditions, the aggregates formed in the blue PEG₄₃‐b‐PSDTE_29close (DTE in closed form) solution were colloidal spheres with solid interiors. The isomerization of DTE pendants could cause the deformation of the vesicle‐like structures. The above results demonstrate a kind of novel photo‐modulated self‐assembly behavior of the amphiphilic diblock copolymer, which could be used for drug‐delivery and other applications.

     

Soft Matter Nanoparticles with Reactive Coronal Pentafluorophenyl Methacrylate Residues via Non‐Polar RAFT Dispersion Polymerization and Polymerization‐Induced Self‐Assembly

Soft matter nanoparticles exhibiting rich polymorphism with reactive pentafluorophenyl methacrylate (PFPMA) units in their coronae were prepared via non‐polar reversible addition‐fragmentation chain transfer dispersion polymerization and polymerization‐induced self‐assembly. Poly(stearyl methacrylate‐stat‐PFPMA) macro‐CTAs, containing up to 12 mol % PFPMA, were used in n‐octane and n‐tetradecane for the subsequent copolymerization of 3‐phenylpropyl methacrylate. Both formulations gave the full, common family of nanoparticles (spheres, worms, and vesicles) as determined by transmission electron microscopy. Reaction of the PFP ester repeating units in the coronal layer of spherical nanoparticles with benzylamine, tetrahydrofurfurylamine, N,N‐dimethylethylenediamine, and an amine functional methyl red dye yielded a new library of functional spherical nano‐objects. The success of the nucleophilic acyl substitution reactions was confirmed using a combination of ¹H/¹⁹F NMR and Fourier transform infrared spectroscopies as well as dynamic light scattering. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2326–2335     

苯乙烯-甲基丙烯酸甲酯嵌段共聚物的合成与表征

采用阴离子聚合技术合成了一系列苯乙烯-甲基丙烯酸甲酯的两嵌段共聚物(PS－b－PMMA)．采用GPC、FTIR、NMR(¹HNMR、¹³CNMR和固体NMR)和DMA等手段进行了表征．结果表明,所得产物为高分子量、窄分布、具有微相分离结构的两嵌段共聚物．     

Synthesis and Characterization of a Block Copolymer Containing Regioregular Poly(3‐hexylthiophene) and Poly(γ‐benzyl‐L‐glutamate)

Poly(3‐hexylthiophene)‐b‐poly(γ‐benzyl‐L ‐glutamate) (P3HT‐b‐PBLG) rod–rod diblock copolymer was synthesized by a ring‐opening polymerization of γ‐benzyl‐L ‐glutamate‐N‐carboxyanhydride using a benzylamine‐terminated regioregular P3HT macroinitiator. The opto‐electronic properties of the diblock copolymer have been investigated. The P3HT precursor and the P3HT‐b‐PBLG have similar UV–Vis spectra both in solution and solid state, indicating that the presence of PBLG block does not decrease the effective conjugation length of the semiconducting polythiophene segment. The copolymer displays solvatochromic behavior in THF/water mixtures. The morphology of the diblock copolymer depends upon the solvent used for film casting and annealing results in morphological changes for both films deposited from chloroform and trichlorobenzene.

     

Preparation of Cross‐Linked Micelles from Glycidyl Methacrylate Based Block Copolymers and Their Usages as Nanoreactors in the Preparation of Gold Nanoparticles

This study reports the synthesis of poly(ethylene glycol)methyl ether‐block‐poly(glycidyl methacrylate) (MPEG‐b‐PGMA) diblock, and poly(ethylene glycol)methyl ether‐block‐poly(glycidyl methacrylate)‐block‐poly(methyl methacrylate) (MPEG‐b‐PGMA‐b‐PMMA) triblock copolymers via atom transfer radical polymerization and their self‐assembly behaviors in aqueous media by using acetone as cosolvent. These block copolymers formed near monodisperse core–shell micelles having cross‐linkable cores. Two types of cross‐linked micelles, namely spherical MPEG‐b‐PGMA core cross‐linked (CCL) micelles and MPEG‐b‐PGMA‐b‐PMMA interlayer cross‐linked (ILCL) micelles, were also successfully prepared from these block copolymers by using various bifunctional cross‐linkers such as hexamethylenediamine (HMDA), ethylenediamine (EDA), and 2‐aminoethanethiol (AET). Cross‐linking was successfully carried out via ring‐opening reactions of epoxy residues of hydrophobic‐cores with primary amine or thiol groups of bifunctional cross‐linkers. Finally, these cross‐linked micelles were successfully used as nanoreactors in the synthesis of gold nanoparticles (AuNPs) in aqueous media. Both CCL and ILCL micelles were found to be good stabilizers for AuNPs in aqueous media. Both CCL‐ and ILCL‐stabilized AuNP dispersions were stable for a long time without any size changes and flocculation at room temperature. These cross‐linked stabilized AuNPs exhibited good catalytic activities in the reduction of p‐nitrophenol. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 514–526.     

Synthesis of Hydroxy‐Functionalized Cyclic Olefin Copolymer and Its Block Copolymers with Semicrystalline Polyolefin Segments

Synthesis of hydroxy‐functionalized cyclic olefin copolymer (COC) is achieved with remarkably high activity (up to 5.96 × 10⁷ g‐polymer mol‐Ti⁻¹ h⁻¹) and controlled hydroxy group in a wide range (≈17.1 mol%) by using ansa‐dimethylsilylene (fluorenyl)(amido)titanium complex. The catalyst also promotes living/controlled copolymerization to afford novel diblock copolymers consisting of hydroxy‐functionalized COC and semicrystalline polyolefin sequence such as polyethylene and syndiotactic polypropylene, where the glass transition temperature of the norbornene/10‐undecen‐1‐ol segment and each block length are controlled by comonomer composition and copolymerization time, respectively.

     

In Situ Visualization of Block Copolymer Self‐Assembly in Organic Media by Super‐Resolution Fluorescence Microscopy

Analytical methods that enable visualization of nanomaterials derived from solution self‐assembly processes in organic solvents are highly desirable. Herein, we demonstrate the use of stimulated emission depletion microscopy (STED) and single molecule localization microscopy (SMLM) to map living crystallization‐driven block copolymer (BCP) self‐assembly in organic media at the sub‐diffraction scale. Four different dyes were successfully used for single‐colour super‐resolution imaging of the BCP nanostructures allowing micelle length distributions to be determined in situ. Dual‐colour SMLM imaging was used to measure and compare the rate of addition of red fluorescent BCP to the termini of green fluorescent seed micelles to generate block comicelles. Although well‐established for aqueous systems, the results highlight the potential of super‐resolution microscopy techniques for the interrogation of self‐assembly processes in organic media.     

Controlled Synthesis and Self‐Assembly of Dopamine‐Containing Copolymer for Honeycomb‐Like Porous Hybrid Particles

Dopamine‐containing monomers, N‐3,4‐dihydroxybenzenethyl methacrylamide (DMA) and dimethylaminoethyl methacrylate (DMAEMA), are successfully copolymerized in a well‐controlled manner via ambient temperature single‐electron transfer initiation and propagation through the radical addition fragmentation chain transfer (SET‐RAFT) method. The controlled behaviors of the copolymerization are confirmed by the first‐order kinetic plots, the linear relationships between molecular weights, and the monomer conversions while keeping relatively narrow molecular weight distribution (M_w/M_n ≤ 1.45). Moreover, biomimetic self‐assembly of poly(N‐3,4‐dihydroxybenzenethyl methacrylamide‐co‐dimethylaminoethyl methacrylate) PDMA‐co‐PDMAEMA and inorganic particles are employed to prepare tunable honeycomb‐like porous hybrid particles (HPHPs) by regulating the predesigned chemical composition. In addition, the inorganic sacrificial templates are successfully selective etched for the formation of porous organic materials.

     

Synthesis,Self‐Assembly,and Multi‐Stimuli Responses of a Supramolecular Block Copolymer

A supramolecular block copolymer is prepared by the molecular recognition of nucleobases between poly(2‐(2‐methoxyethoxy)ethyl methacrylate‐co‐oligo(ethylene glycol) methacrylate)‐SS‐poly(ε‐caprolactone)‐adenine (P(MEO₂MA‐co‐OEGMA)‐SS‐PCL‐A) and uracil‐terminated poly(ethylene glycol) (PEG‐U). Because the block copolymer is linked by the combination of covalent (disulfide bond) and noncovalent (A U) bonds, it not only has similar properties to conventional covalently linked block copolymers but also possesses a dynamic and tunable nature. The copolymer can self‐assemble into micelles with a PCL core and P(MEO₂MA‐co‐OEGMA)/PEG shell. The size and morphologies of the micelles/aggregates can be adjusted by altering the temperature, pH, salt concentration, or adding dithiothreitol (DTT) to the solution. The controlled release of Nile red is achieved at different environmental conditions.

     

One‐Pot Synthesis of Well‐Defined Amphiphilic and Adaptative Block Copolymers via Versatile Combination of “Click” Chemistry and ATRP

Well‐defined amphiphilic PCL‐b‐PDMAEMA block copolymers were successfully synthesized by a combination of ATRP and “click” chemistry following either a commutative two‐step procedure or a straightforward one‐pot process using CuBr · 3Bpy as the sole catalyst. Compared to the traditional coupling method, combining ATRP and click chemistry even in a “one‐pot” process allows the preparation of PCL‐b‐PDMAEMA diblock copolymers characterized by a narrow molecular weight distribution and quantitative conversion of azides and alkynes into triazole functions. Moreover, the amphiphilic character of these copolymers was demonstrated by surface tension measurements and critical micellization concentration was calculated.

     

Synthesis and characterization of polycholesteryl methacrylate–polyhydroxyethyl methyacrylate block copolymers

We report the synthesis and characterization of a series of novel diblock copolymers, poly(cholesteryl methacrylate‐b‐2‐hydroxyethyl methacrylate) (PCMA‐b‐PHEMA). Monomers, cholesteryl methacrylate (CMA) and 2‐(trimethylsiloxy)ethyl methacrylate (HEMA‐TMS), were prepared from methyacryloyl chloride and 2‐hydroxyethyl methacrylate, respectively. Homopolymers of CMA, PCMA, with well‐defined molecular weights and polydispersity indices (PDI), were prepared by reversible addition fragmentation and chain transfer (RAFT) method. Precursor diblock copolymers, PCMA‐b‐P(HEMA‐TMS), were synthesized using PCMA as macromolecular chain transfer agent and monomer, HEMA‐TMS. Product diblock copolymers, PCMA‐b‐PHEMA, were prepared by deprotecting trimethylsilyl units in the precursor diblock copolymers using acid catalysts. Detailed molecular characterization of the precursor diblock copolymers, PCMA‐b‐P(HEMA‐TMS), and the product diblock copolymers, PCMA‐b‐PHEMA, confirmed the composition and structure of these polymers. This versatile synthetic strategy can be used to prepare new amphiphilic block copolymers with cholesterol in one block and hydrogen‐bonding moieties in the second block. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6801–6809, 2008     

Synthesis of Low‐Dimensional Polyion Complex Nanomaterials via Polymerization‐Induced Electrostatic Self‐Assembly

Nanostructured polyion complexes (PICs) are appealing in biomaterials applications. Yet, conventional assembly suffers from the weakness in scale‐up and reproducibility. Only a few low‐dimensional PICs are available to date. Herein we report an efficient and scalable strategy to prepare libraries of low‐dimensional PICs. It involves a visible‐light‐mediated RAFT polymerization of ionic monomer in the presence of a polyion of the opposite charge at 5–50 % w/w total solids concentration in water at 25 °C, namely, polymerization‐induced electrostatic self‐assembly (PIESA). A Vesicle, multi‐compartmental vesicle, and large‐area unilamellar nanofilm can be achieved in water. A long nanowire and porous nanofilm can be prepared in methanol/water. An unusual unimolecular polyion complex (uPIC)‐sphere‐branch/network‐film transition is reported. This green chemistry offers a general platform to prepare various low‐dimensional PICs with high reproducibility on a commercially viable scale under eco‐friendly conditions.     

Strain‐Induced Phase Morphology in Melt Drawn Ultrathin Highly Oriented Block Copolymer Films

A strain‐induced microphase morphology has been established by the melt drawing process in a high molecular weight asymmetric polystyrene‐block‐poly(vinyl‐2‐pyridine) (PS‐b‐P2VP) diblock copolymer. For the first time to the best knowledge of the authors, the melt drawing process has been applied to block copolymers to produce free‐standing, ultrathin block copolymer films with a thickness of ≈100 nm. Intriguingly, during the melt drawing of the polymer a global strain‐induced unidirectional order of the microphase separated needle‐like domains of the block copolymer was generated. This morphology consists of a PS matrix with embedded highly oriented P2VP needle‐like domains oriented parallel to the drawing direction. The needle‐like morphology is explained by a simplified extended chain model of the diblock copolymer chains. Annealing of the films leads to a transition from the strain‐induced needle‐like morphology toward the quasi‐equilibrium sphere‐like morphology.