原子转移自由基聚合法合成PS-g-PMMA

以氯乙酰化聚苯乙烯微球（PS-acyl-Cl）为大分子引发剂,甲基丙烯酸甲酯（MMA）为单体,CuCl/CuCl₂及N,N,N′,N′-四甲基乙二胺（TMEDA）为催化体系的原子转移自由基聚合反应,成功在PS-acyl-Cl表面接枝上PMMA分子链而获得聚苯乙烯 接枝 聚甲基丙烯酸甲酯（PS-g-PMMA）。考察了催化剂、反应温度、溶剂用量等条件对接枝反应的影响,优化的反应条件下,使用氯乙酰基担载量3.44 mmol.g^-1的PS-acyl-Cl,15 h可获得增重率687% 的PS-g-PMMA,且反应表现出一级动力学特征（k=513×10^-5 s^-1）。通过改变反应条件,可得到不同PMMA接枝链长的PS-g-PMMA。反应得到的PS-g-PMMA经水解后有望作为高担载量弱酸型离子交换树脂或进一步功能化后作为酶的柔性固定化载体。     

Micron‐sized membrane reactors: Multicompartment semipermeable polymer particles containing palladium nanoparticles

Multicompartment polymer microparticles are prepared encapsulating palladium nanoparticles within closed‐shell compartments, using a double‐emulsion (W₁/O/W₂), evaporative limited coalescence process. The encapsulation efficiency in some cases is as high as 99%, and very little Pd leaches from the particles. The Pd nanoparticles dispersed in an aqueous environment within the closed‐shell compartments of the microparticles catalyze hydrogenation reactions of low molar mass substrates in water at substantial rates. The microparticle walls serve as semipermeable membranes, permitting diffusion of small molecules into the compartments while retaining the larger metal nanoparticles. The microparticles can be reused after simple filtration. The catalytic activity increases on recycling, possibly because of plasticization of polymer walls by the reactant and products, resulting in increased diffusion. In a second demonstration of catalytic activity, the microparticles efficiently decompose hydrogen peroxide. These nanoparticle‐containing microparticles serve as convenient, reusable catalyst carriers, and prevent inadvertent human and environmental contact with nanoparticles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42021.     

Effect of Basic Factors of Preparation on Characteristics,Hydrolytic Degradation,and Drug Release From Poly(ester-anhydride) Microspheres

Functional poly(ester-anhydride) microspheres were prepared using emulsion solvent evaporation (ESE) and phase inversion methods (PIM). The poly(ester-anhydride)s were obtained by polycondensation of sebacic acid (SBA) and oligo(3-allyloxy-1,2-propylene succinate) terminated with carboxyl groups (OSAGE). The effects of various parameters, including: polymer and emulsifier concentrations, stirring speed and molecular weight of polyvinyl alcohol (PVA) used as emulsifier on size, size distribution and morphology of microspheres obtained by ESE technique were examined. The size of microspheres obtained was in the range 2–30 µm and depended mainly on the stirring rate in emulsion formulation process, as well as concentration of polymer solution used. Molecular weight of PVA, and its concentration in aqueous phase, significantly influenced tendency to agglomeration of microparticles formed, but only slightly changed the size of microspheres. The present study demonstrated that the ESE method can be useful to formulate, from functional poly(ester-anhydride)s, small (2–3 µm) or large (20–30 µm) microspheres with relatively narrow size distribution. Such microspheres were loaded with three model compounds (rhodamine B, p-nitroaniline, and piroxicam) with different water solubility and their release characteristics were examined. In the present study microparticles were also obtained by alternative phase inversion method to compare mainly stability of polymers during formulation of microspheres by both techniques.     

Material encapsulation in poly(methyl methacrylate) shell: A review

Material encapsulation is a relatively new technique for coating a micro/nanosize particle or droplet with polymeric or inorganic shell. Encapsulation technology has many applications in various fields including drug delivery, cosmetic, agriculture, thermal energy storage, textile, and self-healing polymers. Poly(methyl methacrylate) (PMMA) is widely used as shell material in encapsulation due to its high chemical stability, biocompatibility, nontoxicity, and good mechanical properties. The main approach for micro/nanoencapsulation of materials using PMMA as shell comprises emulsion-based techniques such as emulsion polymerization and solvent evaporation from oil-in-water emulsion. In the present review, we first focus on the encapsulation techniques of liquid materials with PMMA shell by analyzing the effective processing parameters influencing the preparation of PMMA micro/nanocapsules. We then describe the morphology of PMMA capsules in emulsion systems according to thermodynamic relations. The techniques to investigation of mechanical properties of capsule shell and the release mechanisms of core material from PMMA capsules were also investigated. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48039.     

单分散油包水乳液制备的研究进展

单分散油包水(W/O)乳液在食品、化妆品、药剂以及高分子微球微囊合成等方面具有广泛的应用。该文综述了近年来单分散W/O乳液的主要制备方法及其基本原理,此外还简要介绍了其在单分散温敏性微球微囊和可生物降解微球微囊合成方面的应用,以期为单分散W/O乳液的制备提供参考。     

Two‐component “Onionlike” micelles with a PPO core,a PDMAEMA shell and a PEO corona: formation and crosslinking

BACKGROUND: Chemical or physical crosslinking of supramolecular assemblies gives them stability in a wide range of environments. Much attention is paid to multilayer (onion‐like) polymeric micelles because their functionality is higher than classic core‐shell micelles. This work reports on the formation and crosslinking of onion‐like micelles prepared by mixing two different block copolymers containing a crosslinkable poly(dimethylaminoethyl methacrylate) (PDMAEMA) block. RESULTS: Block copolymers of a crosslinkable PDMAEMA block were synthesized by atom transfer radical polymerization of 2‐(dimethylamino)ethyl methacrylate (DMAEMA) from poly(propylene oxide) (PPO) or poly(ethylene oxide) (PEO) macroinitiators. The (PDMAEMA₁₃)‐block‐PPO₆₉‐block‐(PDMAEMA₁₃) triblock formed wormlike core‐shell micelles, which were converted into ellipsoidal onion‐like micelles on mixing with the PEO₄₅‐block‐P(DMAEMA₈‐co‐MMA₄) diblock. Onion‐like micelles were crosslinked by quaternization of DMAEMA units. CONCLUSION: Formation of onion‐like micelles by mixing two different AB (ABA) and B′C block copolymers and their subsequent crosslinking is a valuable approach towards stabilized supramolecular assemblies of a higher complexity and functionality than the individual constitutive components. Copyright © 2008 Society of Chemical Industry     

Poly(methylphenylphosphazene)–Graft–Poly(methyl Methacrylate) Copolymers Via Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) was used to graft poly(methyl methacrylate), PMMA, onto poly(methylphenylphosphazene), [(Me)(Ph)PN] _n , PMPP. A two-step process was used to convert a portion of the methyl substituents on [(Me)(Ph)PN] _n to –CH₂C(CH₃)₂OH groups and then to bromoalkyl groups, –CH₂C(CH₃)₂OC(=O)C(CH₃)₂Br, the latter of which served as initiation sites for ATRP of methyl methacrylate (MMA) in the presence of CuCl/bipyridine. Variations in the length of the grafted chains were investigated and the graft copolymers were compared to the parent polymer and blends of similar composition. The new bromoalkyl derivatives of [(Me)(Ph)PN] _n and the PMPP–graft–PMMA copolymers were characterized by elemental analysis, ¹H and ³¹P NMR spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). We dedicate this paper to Professor Harry R. Allcock for consistently maintaining the highest standards in his creative, pioneering work in inorganic rings and polymers.     

Creating monodisperse polymer microspheres using membrane emulsification

This study used membrane emulsification (ME) as a pre‐treatment step to suspension polymerization to produce polystyrene microspheres with diameters from 200 to 300 µm and coefficient of variation (CV) as low 20%. Limited scientific information is available on utilizing suspension polymerization to prepare monodisperse polystyrene microspheres with diameters greater than 100 µm. Microspheres were produced by pumping monomer solution through uniform pores of nickel membranes to form dispersed phase droplets that were transferred to a reactor for suspension polymerization. Systematic studies were done to understand the roles of continuous phase composition, ME unit process parameters, and polymerization reactor stir speed on microsphere size and CV. For a specific microsphere size, there were particular stir speeds in each unit that minimized CV. The methodology developed in this study is being used to prepare monodisperse polymer resin beads to improve detection efficiency and accuracy in flow‐cell sensors for quantifying waterborne radioactivity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44593.     

Polymerized high internal‐phase emulsions: Properties and interaction with water

The synthesis and characterization of novel polymerized high internal‐phase emulsions (polyHIPE) materials are described. Homogeneous, highly porous, low‐density, open‐cell crosslinked copolymers were prepared by polymerizing the continuous phase of HIPE containing styrene and varying amounts of 2‐ethylhexyl methacrylate. The glass transition temperatures (T_gs) of the homopolymers were similar to the literature values, but the copolymer T_gs were lower than expected. These results indicate that the copolymer composition is richer in 2‐ethylhexyl methacrylate than the feed composition. The homopolymer moduli, calculated from the foam moduli, were similar to the literature values. The influence of composition and surface treatment on the water absorbed by the foams was investigated. For example, washing a polyHIPE based on poly(ethylhexyl acrylate) in water at 70°C increased water absorption because of the removal of the residual salt. Adding a fluorinated comonomer to the HIPE reduced hydrophilicity and, thus, water absorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2018–2027, 2002; DOI 10.1002/app.10555     

Catalytic transfer hydrogenation of poly(acryloylmorpholine)-based peptide-resin assemblies and of derived peptide segments

Catalytic transfer hydrogenation using in situ generated Pd black has been used to cleave benzyl ester linked peptides from poly(acryloylmorpholine)-peptide solid (gel) phase assemblies with concurrent removal of peptide N-terminal and side-chain protecting groups. Generation of Pd black in situ also facilitates peptide deprotection by catalytic transfer hydrogenation in free solution.     

A novel amphiphilic AB2 star copolymer synthesized by the combination of ring-opening metathesis polymerization and atom transfer radical polymerization

A new amphiphilic AB₂ star copolymer was synthesized by the combination of ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP). Two different routes (methods A and B) were employed firstly to prepare the poly(oxanorbornene)-based monotelechelic polymers as the hydrophobic arm bearing dibromo-ended group via ROMP in the presence of two different terminating agents catalyzed by first generation Grubbs catalyst. The values of capping efficiency (CE) of the polymers were determined by NMR, which were 94% and 67% for methods A and B, respectively. Then, the dibromo-ended ROMP polymers were used as the macroinitiators for ATRP of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to produce two hydrophilic arms. The prepared amphiphilic AB₂ star copolymers poly(7-oxanorborn-5-ene-exo,exo-2,3-dicarboxylic acid dimethyl ester)-block-bis[poly(2-(dimethylamino)ethyl methacrylate)] (PONBDM_n-b-(PDMAEMA_m)₂) with a fixed chain length of hydrophobic PONBDM and various hydrophilic PDMAEMA chain lengths can self-assemble spontaneously in water to form polymeric micelles, which were characterized by dynamic light scattering, atom force microscopy, and transmission electron microscopy measurements.     

Chitosan‐g‐Polyester Microspheres: Effect of Length and Composition of Grafted Chains

Hydrophobic segments made of oligo(l,l ‐ or d,l ‐lactides) or poly(l,l ‐lactide) are grafted onto chitosan backbone in order to use their amphiphilic behavior to prepare degradable microcarriers intended to be used for tissue engineering. Hydrophilic–lipophilic balance of these copolymers is adjusted playing on the respective length of their hydrophilic and hydrophobic moieties. Thanks to their self‐emulsifying properties, these graft copolymers are processed into microspheres in the absence of hydrophilic emulsifier commonly added in the aqueous phase of the oil/water emulsion. The copolymers containing amorphous oligolactide segments of medium length are demonstrated to be the most effective ones for microparticle fabrication. The microparticles are characterized using SEM, EDX, and FTIR. The reactivity of amine group is demonstrated using fluorescein isothiocyanate staining. The resulting microspheres disclose a porous core and a shell enriched by the hydrophilic polysaccharide moieties. Stabilization of the oil/water interface during the microsphere fabrication, total yield, size distribution, and microparticle surface morphology are mainly affected by the macromolecular features of the copolymers.     

Phase behavior and properties of poly(methyl methacrylate)/poly(vinyl acetate) blends prepared via in situ polymerization

Polymer blends composed of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) were prepared via radical-initiated polymerization of methyl methacrylate (MMA) in the presence of PVAc. Differential scanning calorimetry and dynamic mechanical analysis were employed to investigate the miscibility and phase behavior of the blends. The PMMA/PVAc blends of in situ polymerization were found to be phase separated and exhibited a two-phase structure, although some chain transferring reaction between the components occurred. The phase separation resulted from the solvent effect of MMA during the in situ polymerization, which was confirmed by the investigation of phase behavior based on solution cast blending. Solubility analysis of the polymerized blends indicated that some chain transferring reaction between the components occurred during the polymerization. An abrupt increase in gel content from 21.2 to 72.4 wt % was observed when the inclusion of PVAc increased from 30 to 40 wt %, and the gel component consisted of the component polymers as shown by infrared spectroscopy studies. The thermogravimetric analysis study indicated that the inclusion of a small amount of PVAc gives rise to a marked stabilization effect on the thermal stability. The PMMA/PVAc blends exhibited increased notched impact properties with the inclusion of 5 wt % PVAc. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 675–684, 1998     

Morphology and thermodynamic analysis of composite polymer particles prepared by soap‐free emulsion polymerization in the presence of poly(methyl methacrylate) and polystyrene as biseeds

Biseeds emulsion polymerization was investigated with poly(methyl methacrylate) (PMMA) and polystyrene (PSt) as biseeds and styrene (St) as second‐stage monomer, as well as with thermodynamic analysis; namely, the principle of minimum interfacial free‐energy change was utilized to explain the competitiveness of different seeds for second‐stage monomer and the final equilibrium morphology of composite polymer particles. The experimental results indicated the polymeric particles prepared had bimodal size distribution and the PMMA seed particles showed a higher chance of obtaining St than that of the PSt seed particles, which was in agreement with the computational outcome by the principle of minimum interfacial free‐energy change. Owing to the kinetic factors, the equilibrium morphology could not be reached in the experiments. However, the results demonstrated that double or multiple seeds emulsion polymerization could be used as a model experiment to study the morphology of polymer particle and the morphological prediction. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2675–2680, 2004     

Surface-initiated nitroxide-mediated radical polymerization of 2-(dimethylamino)ethyl acrylate on polymeric microspheres

2-(Dimethylamino)ethyl acrylate (DMAEA) was grafted from the surface of alkoxyamine-functionalized crosslinked poly(styrene-co-chloromethylstyrene) microspheres by nitroxide-mediated radical polymerization (NMRP). Latex particles (∼60 nm diameter) bearing chloromethyl groups were synthesized by emulsion polymerization. N-tert-butyl-N-(1-diethyl phosphono-2,2-dimethylpropyl)nitroxide (SG1) was then immobilized on the particle surface. Microspheres grafted with the homopolymer pDMAEA, as well as block copolymers poly(styrene-b-DMAEA) and poly(butyl acrylate-b-DMAEA) were prepared by surface-initiated NMRP in N,N-dimethylformamide at 112 °C, with the addition of free SG1 to ensure that control is maintained. Particle size increases with number average molecular weight (M_n) of untethered polymers. The polymerizations exhibit linear first order kinetic plots and slight curvature of evolution of M_n with conversion. The functional microspheres were analyzed by infrared spectroscopy, transmission electron microscopy and thermal analysis, as well as their dispersibility in water; the results support the formation of surface-grafted pDMAEA on the microspheres.     

Novel synthesis of poly(methyl methacrylate) brush encapsulated silica particles

Silica (SiO₂)‐crosslinked polystyrene (PS) particles possessing photofunctional N,N‐diethyldithiocarbamate (DC) groups on their surface were prepared by the free‐radical emulsion copolymerization of a mixture of SiO₂ (diameter = 20 nm), styrene, divinyl benzene, 4‐vinylbenzyl N,N‐diethyldithiocarbamate (VBDC), and 2‐hydroxyethyl methacrylate with a radical initiator under UV irradiation. In this copolymerization, the inimer VBDC had the formation of a hyperbranched structure by a living radical mechanism. The particle sizes of such core–shell structures [number‐average particle diameter (D_n) = 35–40 nm] were controlled by the variation of the feed amounts of the monomers and surfactant, or emulsion system. The size distributions were relatively narrow (weight‐average particle diameter/D_n ≈ 1.05). These particles had DC groups on their surface. Subsequently, poly(methyl methacrylate) brush encapsulated SiO₂ particles were synthesized by the grafting from a photoinduced atom transfer radical polymerization approach of methyl methacrylate initiated by SiO₂‐crosslinked PS particles as a macroinitiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The beneficial effect of small amount of water in the ambient temperature atom transfer radical homo and block co-polymerization of methacrylates

ATRP of several methacrylates viz. methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), t-butyl methacrylate (tBMA), benzyl methacrylate (BzMA) and (N,N-dimethylamino)ethyl methacrylate (DMAEMA) has been studied in neat as well as aqueous (up to 12 vol% water) acetone at 35 °C using CuCl/bipyridine (bpy) catalyst and ethyl 2-bromoisobutyrate as the initiator. Addition of water significantly enhances the rate of polymerization without losing control. Unlike CuCl/bpy the CuBr/bpy catalyst gives poor control which is attributed to the lower solubility and consequent heterogeneity in the latter case. Of the other ligands used with the CuCl catalyst viz. o-phenanthroline (o-phen), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), Me₆TREN only o-phen offers reasonably good control. The CuCl/bpy catalyst system has been used also in preparing some di- and tri-block copolymers with reasonably low polydispersity index (PDI) at ambient temperature (35 °C) using aqueous acetone as the solvent. The following block copolymers have been prepared PMMA-tBMA, PMMA-b-tBMA-b-MMA, PMMA-DMAEMA, by this method.     

聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子的制备

由种子乳液聚合法制备了聚苯乙烯-聚甲基丙烯酸甲酯核-壳粒子。以过硫酸钾(KPS)为引发剂,辛基酚聚氧乙烯醚(OP-10)为乳化剂,合成了聚苯乙烯(PS)种子核;连续滴加甲基丙烯酸甲酯(MMA),在核表面富集MMA,制备了粒径范围在0.16~0.67μm的核-壳粒子;当单体苯乙烯与甲基丙烯酸甲酯(St/MMA)的比为30∶70(质量比)时,所得粒径在0.18μm,粒径分布为0.012。差示扫描量热(DSC)研究显示,复合粒子的玻璃化转变温度(Tg)为97.2℃,峰形单一,表现出良好的热性能。     

高吸油性树脂的合成及其性能研究

以自制的甲基丙烯酯十六酸和双烯交联剂为单体,采用悬浮聚合方法合成了聚甲基丙烯酸十六酯高吸油性树脂。研究了悬浮聚合分散剂的种类和用量、聚合反应温度和引发剂用量等对聚合反应体系的分散稳定性和树脂性能的影响,确定了合适的聚合反应工艺条件,长对树脂的吸油性能及其对水面浮油的回收性能进行了考察。     

Effect of in situ polymerization conditions of methyl methacrylate on the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene) PMMA/AES Blends

In this study, the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene‐g‐styrene) (PMMA‐AES) blends were investigated with emphasis on the influence of the in situ polymerization conditions of methyl methacrylate. PMMA‐AES blends were obtained by in situ polymerization, varying the solvent (chloroform or toluene) and polymerization conditions: method A—no stirring and air atmosphere; method B—stirring and N₂ atmosphere. The blends were characterized by infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The results showed that the PMMA‐AES blends are immiscible and present complex morphologies. This morphology shows an elastomeric dispersed phase in a glassy matrix, with inclusion of the matrix in the elastomer domains, suggesting core shell or salami morphology. The occlusion of the glassy phase within the elastomeric domains can be due to the formation of graft copolymer and/or phase inversion during polymerization. However, this morphology is affected by the polymerization conditions (stirring and air or N₂ atmosphere) and by the solvent used. The selective extraction of the blends' components and infrared spectroscopy showed that crosslinked and/or grafting reactions occur on the elastomer chains during MMA polymerization. The glass transition of the elastomer phase is influenced by morphology, crosslinking, and grafting degree and, therefore, T_g depends on the polymerization conditions. On the other hand, the behavior of T_g of the glassy phase with blend composition suggests miscibility or partial miscibility for the SAN phase of AES and PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012