Preparation of poly(methyl methacrylate) grafted hydroxyapatite nanoparticles via reverse ATRP

Surface-initiated reverse atom transfer radical polymerization (reverse ATRP) technical was successfully employed to modify hydroxyapatite (HAP) nanoparticles with poly(methyl methacrylate) (PMMA). The peroxide initiator moiety for reverse ATRP was covalently attached to the HAP surface through the surface hydroxyl groups. Reverse ATRP of methyl methacrylate (MMA) from the initiator-functionalized HAP was carried out, and the end bromide groups of grafted PMMA initiated ATRP of MMA subsequently. Fourier transformation infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) were employed to confirm the grafting and to characterize the nanoparticle structure. The grafted PMMA gave HAP nanoparticles excellent dispersibility in MMA monomer. As the amount of grafted PMMA increased, the dispersibility of surface-grafted HAP and the compressive strength of HAP/PMMA composites were improved.     

A successive route to amphiphilic graft copolymers with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic polystyrene side chains

A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]₀ = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (M_w /M_n = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000     

Iron-mediated AGET ATRP of styrene and methyl methacrylate using ascorbic acid sodium salt as reducing agent

Atom transfer radical polymerization of styrene(St) and methyl methacrylate(MMA) in bulk and in different solvents using activators generated by electron transfer(AGET ATRP) were investigated in the presence of a limited amount of air using FeCl3·6H2O as the catalyst, ascorbic acid sodium salt(AsAc-Na) as the reducing agent, and a cheap and commercially available tetrabutylammonium bromide(TBABr) as the ligand. It was found that polymerization in THF resulted in shorter induction period than that in bulk and in toluene for AGET ATRP of St, while referring to AGET ATRP of MMA, polymerization in THF showed three advantages compared with that in bulk and toluene: 1) shortening the induction period, 2) enhancing the polymerization rate and 3) having better controllability. The living features of the obtained polymers were verified by chain end analysis and chain-extension experiments.     

Polymerization of vinyl monomers by the reaction products of diphenyl sulphoxide with potassium

Diphenyl sulphoxide (DPSO) reacts with an equimolar amount of potassium (K) in tetrahydrofuran (THF) at ?78° to form a reddish-black solution, giving an electron spin resonance (ESR) signal only below ?70°. The signal is attributed to a very labile DPSO anion radical. The solution of DPSO-K (1/1) reaction products reacts further with another molecular amount of K at this temperature to give no ESR signal. The DPSO-K (1/1) reaction products initiates the polymerization of acrylonitrile (AN), but not the polymerizations of methyl methacrylate (MMA), styrene (St) or isoprene (IP). The active species of the solution initiating the polymerization of AN is assumed to be potassium benzene sulphenate from analyses of the solution and the infra-red spectrum of AN oligomers obtained using the complex. The DPSO-K (1/2) reaction products solution initiates the polymerization of MMA, St and IP as well as AN. The active species initiating the polymerization of MMA, St or IP is assumed to be phenylpotassium.     

种子乳液聚合法制备多孔乳胶粒

用批量乳液聚合法制备了苯乙烯（Ｓｔ）———甲基丙烯酸甲酯（ＭＭＡ）二元共聚种子乳液Ｓ１以及Ｓｔ ＭＭＡ 丙烯酸（ＡＡ）三元共聚种子乳液Ｓ２,通过连续法无皂种子乳液聚合合成了一系列不同ＡＡ或ＭＡＡ（甲基丙烯酸）含量的Ｓｔ、ＭＭＡ三元共聚乳液．将所得复合胶乳进行碱／酸分步处理,得到具有多孔结构的乳胶粒．用透射电镜对胶粒形态进行了表征,考察了不饱和酸种类和用量、碱处理初始ｐＨ值及溶胀剂对胶粒成孔的影响．     

ENHANCED MECHANICAL PROPERTIES OF POLYPROPYLENE/SILICA NANOCOMPOSITES WITH SURFACE MODIFICATION OF NANO-SILICA VIA IN SITU COPOLYMERIZATION OF METHYL METHACRYLATE AND BUTYL ACRYLATE

Nano-sized silica particles were modified with methacryloxy-propyltrimethoxysilane(MPS) followed by in situ copolymerization of methyl methacrylate(MMA) and butyl acrylate(BA).These modified nanoparticles were compounded with polypropylene(PP) to prepare PP/silica nanocomposites.PMMA grafted on nano-silica enhances the dispersion of the nanoparticles and interfacial adhesion,decreases the size of PP spherulites in nanocomposites and leads to increasing the Young's modulus and toughness of PP/silica nanoc...     

甲基丙烯酸甲酯/纳米SiO_2粒子分散液的细乳化和细乳液聚合

对包含纳米SiO2粒子的甲基丙烯酸甲酯(MMA)的细乳化和细乳液聚合行为进行了研究.发现在超声细乳化过程中,90%以上的分散于MMA相的纳米SiO2粒子将从油相逃逸到水相.采用甲基丙烯酸3-(三甲氧基甲硅烷基)丙酯(MPS)偶联剂处理SiO2粒子,可以增加其表面亲油性,抑止这种逃逸,经测定几乎全部SiO2粒子在超声细乳化后仍稳定停留在细乳化亚微液滴中.通过进一步细乳液聚合,得到了分散稳定、界面清晰的包裹有纳米SiO2粒子的聚甲基丙烯酸甲酯复合粒子乳液.     

Free-radical cross-linking polymerization of unsymmetrical divinyl compounds 2. Steric effect on gelation in the copolymerizations of allyl methacrylate with several alkyl methacrylates

As an extension of our continuing studies concerned with the free-radical cross-linking polymerization and copolymerization of multivinyl compounds, this article deals with the gelation in the copolymerization of allyl methacrylate (AMA), a typical unsymmetrical divinyl compound containing two types of vinyl groups such as methacryloyl and allyl ones having quite different reactivities, with several alkyl methacrylates, especially focusing on the steric effect of long-chain alkyl groups. Thus, AMA was copolymerized in bulk with methyl methacrylate (MMA), butyl methacrylate (BMA), lauryl methacrylate (LMA), and stearyl methacrylate (SMA) using azo-initiator at 50 °C in the presence of lauryl mercaptan as a chain transfer agent. The actual gel point was compared with the calculated one according to Stockmayer's equation by tentatively supposing equal reactivity of both vinyl groups. In the copolymerizations with LMA and SMA, the suppressed occurrence of intermolecular cross-linking reaction caused by the steric effect of long-chain alkyl groups was clearly observed as a reflection of delayed gelation, whereas the copolymerizations with MMA and BMA were roughly governed by the predominant occurrence of intermolecular cross-linking. These were supported by the conversion dependencies of the molecular-weight distribution profiles, the correlation curve of molecular weight versus elution volume, and the correlation of intrinsic viscosity versus molecular weight of resulting precopolymers.     

Polymerization of vinyl monomers by diphenylsulfone–potassium complexes

Diphenylsulfone (DPSO₂) was found to react with an equimolar amount of potassium in tetrahydrofuran (THF), dimethoxyethane (DME), or diglyme (DG) at reflux or an elevated temperature to yield a reddish-black solution, giving an electron spin resonance (ESR) signal. The signal was attributed to the formation of relatively labile DPSO₂ anion radical. The apparent effects of solvents on the reactivity of DPSO₂ with potassium depended on the polarities and the solvation powers: benzene ? toluene ? dioxane ? tetrahydrofuran < monoglyme < diglyme. The monopotassium complex was found to react further with another molecular amount of the metal to yield a dark blue solution giving no ESR signal. The monopotassium complex initiated the polymerization of acrylonitrile (AN). It did not, however, initiate the polymerization of methyl methacrylate (MMA), styrene (St), or isoprene (IP). The active species of the monopotassium complex that initiated the polymerization of AN was found from analyses of the reaction products and the infrared spectrum of oily oligomer of AN obtained by the complex to be potassium benzenesulfinate. The dipotassium complex was found to initiate the polymerization of MMA, St, IP and AN. The active species of the dipotassium complex that initiated the polymerization of MMA, St, or IP was found from analyses of the reaction products and the infrared spectrum of the oily oligomer of MMA obtained by the complex to be phenyl potassium.     

Transformation of “living” carbocationic and other polymerizations to controlled/“living” radical polymerization

Transformation of “living” carbocationic polymerization of styrene and isobutene to controlled atom transfer radical polymerization (ATRP) is described and formation of the corresponding AB and ABA block copolymers with styrene (St), methyl methacrylate (MMA, methyl acrylate (MA) and isobornyl acrylate (IBA) was demonstrated. A similar approach was applied to the cationic ring opening polymerization of tetrahydrofuran leading to the AB and ABA block copolymers with St, MMA and MA using ATRP. Site transformation approach was also used for the ring opening metathesis polymerization of norbornene and polycondensation systems using polysulfone as an example. In both cases, AB and ABA block copolymers were efficiently formed with styrene and acrylates.     

ANIONIC POLYMERIZATION OF ALKYL METHACRYLATES INITIATED BY nBuCu(NCy2)Li

Anionic polymerization of methyl methacrylate(MMA),n-butyl methacrylate(nBMA)and glycidyl methacrylate (GMA)initiated by nBuCu(NCy_2)Li(1)in tetrahydrofuran(THF)at-50℃to-10℃was investigated.It was found that the polymerization of MMA and nBMA initiated by 1 proceeded quantitatively in THF to afford PMMA and PBMA with polydispersity index 1.15-1.30 and nearly 100%initiator efficiencies at-10℃.The molecular weights increased linearly with the ratio of[monomer]/[1].However,a post-polymerization experiment c...     

Preparation of Al(OH)3/PMMA nanocomposites by emulsion polymerization

Al(OH)₃/PMMA nanocomposites were prepared by the emulsion polymerization of methyl methacrylate (MMA) in the presence of surface‐functionalized Al(OH)₃ particles. Nanosized Al(OH)₃ particles were previously functionalized with a silane coupling agent, 3‐(trimethoxysilyl) propyl methacrylate (γ‐MPS), which was confirmed by FT‐IR and XRF analysis. The average size of seed particles was around 70 nm, and the density of the coupling agent on the particles was calculated to be 8.9 µmol m^?2. The emulsion polymerization was attempted at relatively high solid content of 40–46 wt%. The ratio of the seed particles to MMA had a strong influence on the stability of latex as well as the morphology of composites. Nanocomposites where several PMMA nodules were attached on the surface of Al(OH)₃ core were produced with stable latex emulsion when the weight percents of Al(OH)₃ to MMA were below 20. In the case of higher ratio of 30%, however, the latexes became unstable with an aggregation, and the product morphology was in the shape of large composite. Thermogravimetric analysis showed an improved thermal stability of PMMA composites with the incorporation of Al(OH)₃ nanoparticles. Copyright © 2008 John Wiley & Sons, Ltd.     

丙烯酸酯和甲基丙烯酸酯基团转移共聚研究

研究了三种丙烯酸酯分别和四种甲基丙烯酸酯的基团转移共聚，用１Ｈ ＮＭＲ法测定共聚物组成，扩展的Ｋｅｌｅｎ Ｔｕｄｏｓ法测定竞聚率，结果为γＭＡ＝９２３、γＭＭＡ＝００６；γＥＡ＝１４１５、γＭＭＡ＝００１；γＢＡ＝７５１、γＭＭＡ＝００２；γＭＡ＝１４４１、γＥＭＡ＝００１；γＭＡ＝１３９６、γＢＭＡ＝０２３；γＭＡ＝８６６、γｉ ＢＭＡ＝００８，表明基团转移聚合同阴离子聚合有明显的相似之处．     

Preparation and characterization of acrylic polymer–nanogold nanocomposites from 3-mercaptopropyltrimethoxysilane encapsulated gold nanoparticles

In this study, acrylic polymer–nanogold nanocomposites and their cast films were prepared from an acrylic copolymer and 3-mercaptopropyltrimethoxysilane (MPS) stabilized gold nanoparticles by a sol–gel reaction. The acrylic copolymer was synthesized from methyl methacrylate (MMA) and 3-(trimethoxysilyl)propyl methacrylate (MSMA). The Si–OMe groups of MPS on the surface of gold nanoparticles (MPS–Au) provided the further reaction with the same groups of MSMA, hence the covalent bonds between polymers and MPS–Au nanoparticles were formed. FE-SEM images show MPS–Au nanoparticles are dispersed well in the prepared nanocomposites, and no large aggregation is occurred. TGA results indicate that the decomposed temperatures (T_d) of low Au-content (0.1 wt.%) nanocomposites are higher than these of the acrylic copolymer and high Au-content (1.0 wt.%) nanocomposites. The temperature of maximum decomposed rate (T_p) of each prepared nanocomposite is higher than that of the acrylic copolymer. The hardness of the cast film increases with increasing the Au content. The results show the improved thermal stability and application potentials of the prepared acrylic polymer–nanogold nanocomposites.     

甲基丙烯酸甲酯的反向原子转移自由基聚合反应 研究

在较低的温度(60℃)和较低的AIBN/CuCl~2/配位剂摩尔比(1:2:4)条件下,用乙腈为溶剂,实现了甲基丙烯酸甲酯(MMA)的反向原子转移自由基聚合(RATRP)。联二吡啶(bpy)为配位剂时,所合成的聚甲基丙烯酸甲酯(PMMA)的分子量分布可低至1.08。用1,10-菲咯啉(phen)代替bpy,MMA的聚合反应速率加快,但其分子量分布稍宽(1.40左右),并进一步研究了bpy和phen作为混合配位剂时对MMA反向ATRP聚合的影响。用RATRP反应所得的带有卤素端基的PMMA作为苯乙烯ATRP的大分子引发剂,成功地合成了具有预期结构的苯乙烯与甲基丙烯酸甲酯嵌段共聚物,大分子引发剂的引发效率接近于1,说明在RATRP过程中由自由基引发剂引发MMA进行一般自由基聚合反应的可能性甚微。     

Degradable polymer networks and star polymers based on mixtures of two cleavable dimethacrylate crosslinkers: Synthesis,characterization, and degradation

Mixtures of two cleavable dimethacrylate crosslinkers, the hydrolyzable di(methacryloyloxy‐1‐ethoxy)methane (DMOEM) and the thermolyzable 1,1‐ethylenediol dimethacrylate (EDDMA), were used for the preparation of neat crosslinker polymer networks, randomly crosslinked polymer networks of methyl methacrylate (MMA), and star polymers of MMA, using group transfer polymerization in tetrahydrofuran (THF). All star polymers and randomly crosslinked polymer networks containing mixtures of the hydrolyzable DMOEM and the thermolyzable EDDMA crosslinkers gave THF‐soluble final products when subjected to sequential thermolysis and hydrolysis, in this order. When applying sequential hydrolysis and thermolysis, only the star polymers with an EDDMA crosslinker content equal to or higher than 50% gave THF‐soluble final products. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5853–5870, 2009     

无皂乳液聚合法制备P(St-MMA-SPMAP)单分散乳胶颗粒

利用无皂乳液聚合 ,分别用一步法和两步法合成了单分散的聚 (苯乙烯 甲基丙烯酸甲酯 甲基丙烯酸丙基磺酸钾 ) (P(St MMA SPMAP) )乳胶颗粒 .在该聚合体系中 ,当水溶性磺酸基单体SPMAP的浓度小于 17mmol L时 ,为均相成核过程 ,能制备单分散的乳胶颗粒 .其中 ,用两步法制备的乳胶颗粒相互之间无粘连 .此外 ,还对一步法合成苯乙烯 甲基丙烯酸甲酯 甲基丙烯酸辛基磺酸钠 (P(St MMA SOMAS) )乳胶颗粒进行了初步研究 .     

Synthesis of well‐defined polymer brushes on the surface of zinc antimonate nanoparticles through surface‐initiated atom transfer radical polymerization

Zinc antimonate nanoparticles consisting of antimony and zinc oxide were surface modified in a methanol solvent medium using triethoxysilane‐based atom transfer radical polymerization (ATRP) initiating group (i.e.,) 6‐(2‐bromo‐2‐methyl) propionyloxy hexyl triethoxysilane. Successful grafting of ATRP initiator on the surface of nanoparticles was confirmed by thermogravimetric analysis that shows a significant weight loss at around 250–410 °C. Grafting of ATRP initiator onto the surface was further corroborated using Fourier transform Infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS). The surface‐initiated ATRP of methyl methacrylate (MMA) mediated by a copper complex was carried out with the initiator‐fixed zinc antimonate nanoparticles in the presence of a sacrificial (free) initiator. The polymerization was preceded in a living manner in all examined cases; producing nanoparticles coated with well defined poly(methyl methacrylate) (PMMA) brushes with molecular weight in the range of 35–48K. Furthermore, PMMA‐grafted zinc antimonate nanoparticles were characterized using Thermogravimetric analysis (TGA) that exhibit significant weight loss in the temperature range of 300–410 °C confirming the formation of polymer brushes on the surface with the graft density as high as 0.26–0.27 chains/nm². The improvement in the dispersibility of PMMA‐grafted zinc antimonate nanoparticles was verified using ultraviolet‐visible spectroscopy and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Photocrosslinking of polymethoxymethylstyrene and copolymers containing (2,2-disubstituted-1,3-dioxolan-4-yl)methoxymethylstyrene

Methoxymethylstyrene (MSt), (2,2-dimethyl-1,3-dioxolan-4-yl)methoxymethylstyrene (MMSt), and (2-ethyl-2-methyl-1,3-dioxolan-4-yl)methoxymethylstyrene (EMSt) were synthesized and homopolymerized and copolymerized. The photochemical behavior of resultant homopolymers and copolymers with methyl methacrylate (MMA) and styrene (St) were investigated. The infrared (IR) and ultraviolet (UV) spectra of poly(MSt) showed that new bands ascribed to methyl benzoate residue increase rapidly with irrdiation time in air, but no detectable changes are observed in vacuum. The solubility measurements of poly(MSt) indicate that the main factor in crosslinking is the direct coupling of the benzyl radical generated by UV irradiation, which was confirmed by photopolymerization of MMA by means of benzyl methyl ether. It was also found that copolymers of MMSt or EMSt with MMA or St are easily crosslinked by UV irradiation. From the results of solubility measurements of these copolymers irradiated both in air and in vaccum, it was concluded that not only the 1,3-dioxolane structure but also the benzyl methyl ether structure takes part in photocrosslinking, as we expected.     

COPOLYMERIZATION PROCESS OF TRIPHENYLMETHYL METHACRYLATE AND MMA WITH CHIRAL ANIONIC COMPLEX INITIATOR

The copolymerization process of triphenylmethyl methacrylate (TrMA) and methylmethacrylate (MMA) using chiral anionic complex initiator (-) SP-FlLi (Scheme 1) has beenstudied in toluene and THF, respectively. The copolymer obtained in toluene possessed muchhigher specific rotation than that in THF. These copolymers have shown a tendency to a random and a like alternating structure, respectively.