两亲性无规聚合物P（MMA-co-MAA）的合成及其自组装研究

由疏水性单体甲基丙烯酸甲酯（MMA）和亲水性单体甲基丙烯酸（MAA）进行自由基溶液共聚,合成了一系列配比不同的两亲性无规聚合物P（MMA-co-MAA）,用红外光谱、核磁共振和凝胶渗透色谱对聚合物结构进行了表征。采用一种操作过程简单、快捷、环保的新方法制备了聚合物胶束,即将一定质量的聚合物溶于碱性水溶液中,通过中和原理进行自组装,并得到球形胶束。通过透射电子显微镜（TEM）和激光光散射（DLS）法,研究了聚合物中基团摩尔比例不同时对胶束形貌和流体动力学半径（Rh）的影响。     

两亲性无规聚合物P(MMA-co-MAA)的合成及其自组装研究

由疏水性单体甲基丙烯酸甲酯(MMA)和亲水性单体甲基丙烯酸(MAA)进行自由基溶液共聚,合成了一系列配比不同的两亲性无规聚合物P(MMA-co-MAA),用红外光谱、核磁共振和凝胶渗透色谱对聚合物结构进行了表征。采用一种操作过程简单、快捷、环保的新方法制备了聚合物胶束,即将一定质量的聚合物溶于碱性水溶液中,通过中和原理进行自组装,并得到球形胶束。通过透射电子显微镜(TEM)和激光光散射(DLS)法,研究了聚合物中基团摩尔比例不同时对胶束形貌和流体动力学半径(Rh)的影响。     

Amphiphilic block copolymers with pendant thiol groups in side chains by RAFT polymerization

A new synthetic approach to thiol functional, well-defined amphiphilic block copolymers, which can be used to prepare multifunctional polymers and polymeric nanoparticles, is presented. Starting with a hydrophilic macroRAFT transfer agent and hydrophobic (meth)acrylate monomers that possess protected thiol groups, amphiphilic block copolymers are prepared in high yield. It is proven that the protected thiol groups in the monomer do not interfere with the RAFT polymerization process. Polymers with defined molecular weight, narrow polydispersities (PDI < 1.30) and varying length of the hydrophobic block are presented. Polymers with thiol groups in side chains and chain ends are obtained by aminolysis. With pyrene fluorescence spectroscopy and NMR measurements, it is shown that all synthesized polymers self-assemble into micelles. Furthermore, the possible application of these new polymers is exemplified by the preparation of polymer nanoparticles.     

Synthesis of phenylphosphinic acid-containing amphiphilic homopolymers by reversible addition-fragmentation transfer (RAFT) polymerization and its aggregation in water

A novel amphiphilic phosphorus-containing polymer was prepared by RAFT polymerization of 3-[2-(acryloyloxy)ethoxy]-3-oxopropyl(phenyl) phosphinic acid (AOPA). The monomer was first synthesized by esterification of 3-[hydroxy(phenyl)phosphoryl]propanoic acid and 2-hydroxyethyl acrylate, and then the polymerizations were performed at 60 °C. The polymerization was well controlled, and the polymers with “well-defined” structures were successfully synthesized. The polymers can self-assemble to form the micelles in distilled water due to the special amphiphilic structure, and the shell of the micelles could be cross-linked by the coordination of phosphinic acid with cations. The property may promote the polymers to be used in the ionic exchange for the environment protection.     

Supramolecular structures of an amphiphilic hairy-rod conjugated copolymer bearing poly(ethylene oxide) side chain

The structures of an amphiphilic conjugated graft copolymer, poly(2,3-diphenyl-5-(trimethylene-heptadeca(oxyethylene)-methoxy-phenylene vinylene) (denoted as PVEO₁₇) composing of a conjugated DP-PPV backbone and PEO side chains, in bulk and solutions with tetrahydrofuran (THF) and water have been investigated by small-angle X-ray scattering (SAXS). In bulk state, the DP-PPV main chains in PVEO₁₇ stacked to form flat disk microdomains dispersed in the PEO side-chain matrix. The corresponding wide angle X-ray scattering pattern revealed the existence of crystallinity of the PEO side chains. The structure of the polymer in solution was affected by the solvent quality and the polymer concentration. PVEO₁₇ chains were relatively well dispersed in THF. In aqueous solutions, however, the amphiphilic PVEO₁₇ chains aggregated significantly over the concentration range of 1–8 wt%, where the polymer was found to self-organize to form cylindrical micelles with the aggregation number increasing with the increase of concentration. The photophysical properties characterized by UV–Vis and photoluminescence spectroscopy were strongly affected by the aggregation state of the polymer.     

Ultra-thin films of cationic amphiphilic poly(2-(dimethylamino)ethyl methacrylate) based block copolymers as surface wettability modifiers

Ultra-thin films of cationic amphiphilic block and statistical copolymers were applied on silica surfaces from aqueous solutions through electrostatic interactions, and the resulting modification in the wettability of the surfaces was studied. A copolymer series from 2-(dimethylamino)ethyl methacrylate with methyl methacrylate and butyl methacrylate was polymerized by ATRP. Subsequently, the conformation of the polymers in aqueous solutions was studied by surface tension measurements, dynamic light scattering, ¹H NMR and cryogenic transmission electron microscopy. Unimeric conformation, equilibrium micelles or frozen micellar structures were observed, depending on polymer composition and the ionic strength of the solution. The polymers were applied on silica from aqueous solutions by either spin coating or adsorption. The formed ultra-thin film surfaces were studied by AFM and water contact angle measurements. The spin-coated surfaces were highly hydrophilic with rapidly dropping contact angles, whereas the surfaces prepared by adsorption had stable water contact angles between 30-60°, depending on polymer. The difference between the spin-coated and adsorbed surfaces is explained by the formation of a monolayer in the adsorbed surfaces.     

Controlled grafting of poly(vinyl acetate) onto starch via RAFT polymerization

A structure‐exact starch‐based xanthate agent was prepared and used as chain transfer agent to mediate RAFT polymerization of vinyl acetate, which offered a convenient way to well control the structure and composition of starch‐g‐poly(vinyl acetate). The structures of the intermediate and the polymer were verified with FTIR and ¹H‐NMR. Gel permeation chromatography measurement results indicated that the polymerization was performed as expected. It was found that the relationship between number average molecular weight and monomer conversion was linear. The polydispersity index of grafted side‐chain ranged from 1.19 to 1.53 and most of them were around 1.2. There was one more degradation stage appeared on the thermogravimetric analysis profile of starch‐g‐poly(vinyl acetate) than that of starch. TEM observation exhibited that the product was able to self‐assemble into micelles in aqueous solution, which suggested the copolymer was amphiphilic. Both the thermal and amphiphilic properties demonstrated the starch‐g‐poly(vinyl acetate) was successfully synthesized as well. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

HPAM-g-P(NIPA-co-DMAM)的合成与温敏行为

利用端基转换法合成了不同组成及相对分子质量的端丙烯酰胺基聚（N-异丙基丙烯酰胺-co-N,N-二甲基丙烯酰胺）［poly(NIPA-co-DMAM), PID］大分子单体;与丙烯酰胺聚合后再水解，得到以PID为侧链，浊点在37～63℃的接枝共聚物［HPAM-g-P(NIPA-co-DMAM), HGPID］。利用¹H NMR及端基分析等对大分子单体和接枝物的组成及结构进行了表征;考察了接枝共聚物侧链的组成和链长、共聚物质量浓度和外加盐浓度等因素对其水溶液的热敏特性及温敏增稠性的影响。     

两亲性超支化聚合物研究进展

介绍了两亲性超支化聚合物的合成方法,利用长链烷基和聚乙二醇对超支化聚合物端基接枝改性;或者对超支化聚合物改性引入活性位点,再利用其引发乙烯基单体,通过自由基聚合、开环聚合得到两亲性超支化聚合物。阐述了不同结构的两亲性超支化聚合物在溶液中的独特性质,如核壳型单分子胶束以及不同胶束形态的聚集体。详细介绍了两亲性超支化聚合物在药物输送载体、材料改性以及染料分子的封装等领域的应用现状,指出采用新的改性技术、聚合技术制备具有特殊性能的两亲性超支化聚合物以及探索其在生物医药领域的研究为今后的主要发展方向。     

Ring-opening polymerization of cyclic esters by cyclodextrins

Synthetic polymers, typically prepared by addition polymerization or stepwise polymerization, are used constantly in our daily lives. In recent years, polymer scientists have focused on more environmentally friendly synthetic methods such as mild reaction conditions and biodegradable condensation polymers, including polyesters and polyamides. However, challenges remain in finding greener methods for the synthesis of polymers. Although reactions carried out in water are more environmentally friendly than those in organic solvents, aqueous media can lead to the hydrolysis of condensation polymers. Furthermore, bulk polymerizations are difficult to control. In biological systems, enzymes synthesize most polymers (proteins, DNAs, RNAs, and polysaccharides) in aqueous environments or in condensed phases (membranes). Most enzymes, such as DNA polymerases, RNA polymerases, and ribosomes, form doughnutlike shapes, which encircle the growing polymer chain. As biopolymers form, the active sites and the substrate-combining sites are located at the end of the growing polymer chain and carefully control the polymerization. Therefore, a synthetic catalyst that could insert the monomers between the active site and binding site would create an ideal biomimetic polymerization system. In this Account, we describe cyclodextrins (CDs) as catalysts that can polymerize cyclic esters (lactones and lactides). CDs can initiate polymerizations of cyclic esters in bulk without solvents (even water) to give products in high yields. During our studies on the polymerization of lactones by CDs in bulk, we found that CDs function not only as initiators (catalysts) but also as supporting architectures similar to chaperone proteins. CDs encircle a linear polymer chain so that the chain assumes the proper conformation and avoids coagulation. The CDs can mimic the strategy that living systems use to prepare polymers. Thus, we can obtain polyesters tethered to CDs without employing additional solvents or cocatalysts. Although CD has many hydroxyl groups, only one secondary hydroxyl group attaches to the polyester chain. In addition, the polymerization is highly specific for monomer substrates. We believe that this is the first system in which the catalyst includes monomers initially and subsequently activates the included monomers. The catalyst then inserts the monomers between the binding site and the growing chain. Therefore, this system should provide a new environmentally friendly route to produce biodegradable functional polymers.     

Self-assembly and sol-to-gel transition of thermosensitive methoxy-polyethylene glycol-polyalanine block copolymer hydrogels

Certain amphiphilic polymers can self-assemble to form various structures, such as micelles and hydrogels in aqueous medium, depending on the concentration or temperature. These different structures have found many applications in biomedical and material processing fields. The assembly processes of the polypeptide-containing diblock copolymer, methoxy poly(ethylene glycol)-block-poly(L-alanine) (mPEG-PA), was studied to elucidate the relationship between different structures with parameters such as chain lengths (volume fraction) of the two blocks, molecular weights, medium polarity, temperature, and concentration. Gelation mechanism was especially focused in the study. Various solution-cast morphologies observed by scanning electron microscopy (SEM) imaging including cylinders and micelles aggregates can be obtained by using solvents with different polarity for casting with simply tuning the chain lengths. The sol-to-gel transition mechanism can be best explained by phase separation between polymer-rich and water-rich phases. It might be spinodal decomposition process to cause the phase separation. Furthermore, the branch and flack structures can be observed due to phase separation mechanism and different chain lengths by SEM images. This result offers new insights into behavior of mPEG-PA system, enabling more controlled manipulation to various applications.     

Investigation of local viscosity in polymer solutions by means of electrolytic conductivity

The local viscosity in aqueous solutions of polymers (dextran and hydroxyethl cellulose) and low-molecular weight viscogenic compounds (glycerol and d-glucose) has been studied by measuring the electrolytic conductivity of probe electrolytes. For low-molecular weight viscogenic compounds the local viscosities determined were close to the macroscopic viscosities of the solutions, whereas pronounced differences exist for polymer solutions. Of particular interest was the finding that the local viscosity for dextran was only marginally higher than the local viscosity for the corresponding monomer, d-glucose. The local viscosity for hydroxyethyl cellulose was somewhat higher than the local viscosity for dextran, indicating greater flexibility of the dextran chain.     

Synthesis, characterization and evaluation of amphiphilic diblock copolymer emulsifiers based on methoxy hexa(ethylene glycol) methacrylate and benzyl methacrylate

Linear, amphiphilic diblock copolymers based on the nonionic, hydrophilic monomer methoxy hexa(ethylene glycol) methacrylate (HEGMA) and the hydrophobic monomer benzyl methacrylate (BzMA) of different molecular weights and compositions were synthesized by group transfer polymerization. The molecular weights and comonomer compositions of these copolymers were characterized by gel permeation chromatography and proton nuclear magnetic resonance (¹H NMR) spectroscopy, respectively. Dynamic light scattering on aqueous solutions of the diblock copolymers indicated that all the copolymers formed aggregates whose size increased with the % w/w BzMA composition and with the overall molecular weight of the linear chains. Turbidimetry on 1% w/w aqueous copolymer solutions was used to determine the cloud points, which were found to increase with the composition in hydrophilic units and the linear chain molecular weight. After polymer characterization, xylene/water and diazinon (pesticide)/water emulsions were prepared using the above polymers as stabilizers at 1% w/w polymer concentration and at different overall organic phase/water ratios. At an organic phase/water mass ratio of 4/1, the lower molecular weight (2500 and 5000 g mol⁻¹) diblock copolymers provided stable single-phase o/w emulsions, matching the behavior of commercially available hydrophilic Pluronics.     

Liquid crystalline polysurfactant

Summary A new kind of amphiphilic polymer (PAMC₁₆S) has been synthesized where the amphiphilic moiety is attached as a side chain via the hydrophilic end to the polymer backbone. DSC, POM, and WAXD study revealed that the polysurfactant formed thermotropic liquid crystalline phase. The liquid crystalline domains appeared after annealed at the melt for a period of time, and evolved with annealing. It was indicated that the thermodynamic effect played a significant role on the self—aggregation of hydrophobic ends, so as to form liquid crystalline structure. X—ray investigation suggested that the mesophase structure could be described as smectic with lamellar type of packing, in which alkyl tails aggregated to form layer. A model of supermolecular structure was given.     

Three different types of quasi-model networks: synthesis by group transfer polymerization and characterization

Summary Group transfer polymerization (GTP) chemistry was employed for the preparation of polymethacrylate networks of controlled structure (quasi-model networks) of three different types: (a) regular quasi-model networks, in which all polymer chains were linked at their ends, leaving, in principle, no free chain ends, (b) crosslinked star polymer quasi-model networks, in which star polymers were interlinked via half of their chains, letting the other half free (dangling), and (c) shell-crosslinked polymer quasi-model networks, in which the outer part of the network contained polymer arms (dangling chains). Combination of hydrophilic and hydrophobic monomers led to amphiphilic networks whose aqueous swelling behavior was characterized gravimetrically.     

Photosensitive micelles based on polysiloxanes containing azobenzene moieties

Photosensitive micelles based on amphiphilic azo-polysiloxanes were obtained and characterized. The amphiphilic polymers were synthesized in a two-step reaction, starting from a polysiloxane containing chlorobenzyl groups in the side chain. In the first step, the polysiloxane was modified with azo-aromatic groups (35–45% substitution degree) and in the second step the unreacted chlorobenzyl groups were quaternized, using different tertiary amines. The structure of the polysiloxanes and their aggregation/disaggregation capacity were evaluated by 1H-NMR, DSC, fluorescence and UV–VIS spectroscopy, dynamic light scattering and transmission electron microscopy. All the amphiphilic polysiloxanes are capable of generating micelles, the critical concentration of the aggregation values being situated in the range 10⁻³–10⁻² g/L. As a function of the ternary amine structure used in the quarterisation reaction, the micellar aggregation process is different, individual micelles or micellar clusters being obtained. The clusters' dimension cannot be controlled, the polydispersity index having high values. The disaggregation processes of the micelles under UV irradiation reveal that the polymer chemical structure influences the aggregates stability. A total micelles disaggregation was obtained for the polysiloxane modified with azophenol and amine containing a long hydrocarbon segment. In the other cases, only a partially disaggregation process takes place.     

Refractive index changes in polyacrylates bearing alkyl sulfur groups through the sulfur oxidation reaction

Four polyacrylates with sulfur-containing side chains were prepared to examine the changes in refractive index (RI) induced by sulfur oxidation. Linear alkyl sulfides and alicyclic sulfides, such as 1,3-dithiolane and 1,4-dithiane, were introduced to impart large RIs to polyacrylates. Oxidation of the sulfur polymers by O₃ and m-chloroperoxybenzoic acid led to the formation of the corresponding sulfoxide and sulfone polymers, respectively. Sulfur oxidation occurred completely, which was highlighted by the oxidized polymer exhibiting a refractive index comparable to a polymer that was synthesized using a sulfone monomer. The RI of the linear sulfur polymer increased and decreased due to the formation of sulfoxide and sulfone polymers, respectively. The Abbe number of the polymer with a linear sulfide side chain was 33.4, which increased to 48.7 after oxidation.     

Synthesis of an amphiphilic copolymer bearing rhodamine moieties and its self-assembly into micelles as chemosensors for Fe in aqueous solution

We report on the fabrication of an amphiphilic random copolymer-based colorimetric and fluorescent chemosensor for Fe³⁺ ions that was prepared by free radical polymerization of a novel rhodamine-based Fe³⁺-recognizing monomer, R6GEM, with N-vinylpyrrolidone (NVP). Because of its amphiphilic property, the copolymer P(NVP-co-R6GEM) can self-assemble into micelles, which allows it to be used as a chemosensor in aqueous solution. Upon addition of Fe³⁺ ions to the micelle solution, visual color change and fluorescence enhancement were observed. Moreover, other metal ions did not induce obvious changes to the absorption and fluorescence spectra. The water dispersibility and biocompatibility of these polymer micelles could provide a new strategy for detecting analytes in environmental and biological systems.     

Polymer–surfactant interactions in graft copolymer solutions

Graft copolymers composed of water-soluble cellulosic backbones and > 0.4% (by weight) alkyl grafts are insoluble in water but soluble in surfactant solutions. Studies of the bulk viscosity and stability of polymer-surfactant solutions at 49°C indicate that the mechanism for solubilization of the polymer is the incorporation of the alkyl side chains into surfactant micelles. The tendency for side chains to combine with micelles appears to depend at least in part on the geometry of the surfactant tail group such that surfactants containing straight-chain tail groups solubilize alkyl side chains more readily than olefinic surfactants. The presence of small solutes near the surface of the micelle also inhibits incorporation of side chains from the polymer. Unsolubilized side chains remain in the aqueous phase of the solution, where they form thermally unstable intermolecular aggregates.