Influence of HMTA ligand in MMA AGET ATRP emulsion polymerization

Interactions of hexamethylenetetramine ligand in atom transfer radical polymerization initiated by activator generated by electron transfer were studied. Polymerization of methyl methacrylate was done using two-step experimental procedure in 2 L emulsion batch reactor at 50, 60, and 80°C. The selection of reactant ratios was quite challenging for a reactor of this size. Replicate runs were conducted for data reproducibility purpose. Gravimetry method and gel permeation chromatography were used to determine monomer conversion, Mn, and PDI of polymer samples. PMMA produced was also characterized by means of dynamic light scattering, Fourier-transform infrared spectroscopy and nuclear Magnetic Resonance spectroscopy. Results showed high monomer conversion up to 93% and Mn ranging 243–274 kg/mol with PDI from 1.45 to 1.60. Besides, combining HMTA with sodium dodecyl sulfate, an anionic surfactant, a well-controlled polymer with a lower Mn of 201 kg/mol and PDI of 1.56 was obtained in 3 hr reaction time.     

Synthesis and characterization of functional gradient copolymers of glycidyl methacrylate and butyl acrylate

Epoxy-functional spontaneous gradient copolymers of glycidyl methacrylate (G) and n-butyl acrylate (B) were synthesized via atom transfer radical polymerization (ATRP). The copolymerization reactions were carried out in toluene solution at 70 °C, using methyl 2-bromopropionate (MBrP) as initiator and copper chloride with N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The kinetic behaviour of the statistical copolymerizations was studied in a wide composition interval with molar fractions of G ranging from 0.10 to 0.75. The synthesized copolymers were characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. ¹H NMR was employed to determine the copolymer composition, demonstrating the gradient character of the copolymers along the main chain in the whole monomer conversion interval. Apart from this, the sequence distribution and stereoregularity were analyzed. These microstructural experimental data agreed well with those calculated from Mayo-Lewis terminal model (MLTM) and a Bernoullian statistic with an isotacticity parameter of σ_G = 0.28 and a coisotacticity parameter of σ = 0.30.     

A novel poly(p-phenylene vinylene)-b-poly(methyl methacrylate) rod-coil diblock copolymer

In this letter, a novel well-defined PPV-b-PMMA rod-coil diblock copolymer, consisting of PPV oligomer as its rod block and PMMA as its coil block, respectively, was prepared via ATRP for the first time. The structure of the copolymer was determined by the measurements of FTIR, ¹H NMR and gel permeation chromatography (GPC). The thermal and optical properties of the copolymers are investigated by DSC, TGA, UV-Vis and photoluminescence (PL) spectra. The results showed that, the introduction of PMMA coil block can improve both the thermal stability and optical properties of PPV oligomer. The highly ordered hexagonally honeycomb-structured film of the copolymer fabricated by vaporizing solvent is also investigated by optical microscope and SEM.     

Fabrication of poly(PEGMA) surface with controllable thickness gradient and its mediation on the gradient adhesion of cells

The gradient surface shows enormous potential in the development of tissue engineering, biosensor, microfluidic control, and particle sorting. In this work, a poly(polyethyleneglycol methacrylate) (poly(PEGMA)) gradient surface was prepared through surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-AGRET ATRP). The effect of various parameters on the thickness growth of poly(PEGMA) film were analyzed, among which the excessive reducing agent was utmost important. The reducing agents supported the regeneration of Cu^I and eliminated the disturbance of air, maintaining the "living polymerization" of poly(PEGMA) up to 73.1 nm under tested conditions. The physicochemical properties of the fabricated surfaces were characterized by ellipsometry, X-ray photoelectron spectroscopy, water contact angle. The thickness slope of gradient poly(PEGMA) was controllable in a nanoscale range. The gradient surface was further grafted with CRGD (Cys-Arg-Gly-Asp) peptides onto the poly(PEGMA-co-[glycidyl methacrylate]) blocks via the ring-opening reaction between epoxy and amino groups, which showed a gradient change in water contact angle and adhesion of endothelial cells.     

活性自由基乳液聚合的研究进展

活性自由基乳液聚合是一个非常新的研究领域。介绍了目前活性自由基乳液聚合领域的3种常用的方法及应用这些方法进行乳液聚合的研究进展,包括:原子转移自由基聚合(ATRP),氮氧调节自由基聚合(NMP)和可逆加成-断裂链转移自由基聚合(RAFT)。     

Surface‐initiated atom transfer radical polymerization from Mg(OH)2 nanoparticles to prepare the well‐defined polymer‐Mg(OH)2 nanocomposites

Well‐defined polymer‐Mg(OH)₂ nanocomposites were prepared by atom transfer radical polymerization (ATRP). The ATRP initiators were covalently attached to the Mg(OH)₂ by esterification of 2‐chloropropionyl chloride with hydroxyl group. The amount of polymer grafted from Mg(OH)₂ can be controlled using a different catalyst system and adding a small amount of polar solvent. The well‐defined diblock copolymer, consisting of poly(styrene) (PS) and poly(methyl methacrylate) (PMMA) were synthesized. The products were characterized by nuclear magnetic resonance, Fourier transform infrared, differential scanning calorimetry, and thermal gravimetric analysis. The morphologies of PS/PMMA and PS/PMMA/Mg(OH)₂‐g‐PS‐b‐PMMA blends are compared by using a scanning electron microscope. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3680–3687, 2007     

Synthesis and characterization of poly(vinyl chloride‐co‐vinyl acetate)‐graft‐poly[(meth)acrylates] by atom transfer radical polymerization

The graft polymerization of methyl methacrylate and butyl acrylate onto poly(vinyl chloride‐co‐vinyl acetate) with atom transfer radical polymerization (ATRP) was successfully carried out with copper(I) thiocyanate/N,N,N′,N′,N″‐pentamethyldiethylenetriamine and copper(I) chloride/2,2′‐bipyridine as catalysts in the solvent N,N‐dimethylformamide. For methyl methacrylate, a kinetic plot of ln([M]₀/[M]) (where [M]₀ is the initial monomer concentration and [M] is the monomer concentration) versus time for the graft polymerization was almost linear, and the molecular weight of the graft copolymer increased with increasing conversion, this being typical for ATRP. The formation of the graft polymer was confirmed with gel permeation chromatography, ¹H‐NMR, and Fourier transform infrared spectroscopy. The glass‐transition temperature of the copolymer increased with the concentration of methyl methacrylate. The graft copolymer was hydrolyzed, and its swelling capacity was measured. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 183–189, 2005     

Atom transfer radical polymerization of n‐butyl methacrylate in an aqueous dispersed system

Atom transfer radical polymerization of n‐butyl methacrylate (BMA) was conducted in an aqueous dispersed system with different kinds of copper complexes. The partitioning behavior of the copper complexes, including CuCl/4,4′‐di(5‐nonyl)‐2,2′‐bipydine (dNbpy), CuCl₂/dNbpy, CuCl/2,2′‐bipydine (bpy), CuCl₂/bpy, CuCl/bis(N,N′‐dimethylaminoethyl)ether (bde), and CuCl₂/bde between the monomer (BMA), and water was studied in detail with ultraviolet‐visible spectroscopy. The results show that with a less hydrophobic ligand, such as bpy or bde, most of the Cu(I) or the Cu(II) complexes migrated from the BMA phase to the aqueous phase, the atom transfer equilibrium was destroyed, and the polymerization was nearly not controlled; it converted to classical emulsion polymerization. As to the very hydrophobic ligand dNbpy, although the partitioning study of the copper complexes indicated that not all the copper species were restricted to the organic phase, the linear correlation between the molecular weight and the monomer conversion and the narrow polydispersities confirmed that the polymerization was still quite well controlled. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3175–3179, 2003     

离子化对SBS/聚(苯乙烯-甲基丙烯酸甲酯)热塑性互穿聚合物网络结构与力学性能影响的研究

采用原子转移自由基聚合（ATRP）法合成了聚（苯乙烯一甲基丙烯酸甲酯）[P（St—MMA）]，采用两步法制备了SBS／P（St—MMA）热塑性互穿聚合物网络（TIPN）。在双螺杆挤出机上通过熔融挤出方法对SBS／P（St—MMA）直接进行水解，制备了含有离子键的SBS／P（St—MMA）TIPN。离子化后TIPN的拉伸强度明显增加，在离子化程度为25％时达到最大，断裂伸长率明显下降。TIPN的中PB和PS嵌段的Tg均明显增加，PS嵌段增加更加明显，提高20℃；弹性模量E’均明显提高。