Synthesis and properties of star‐shaped polymers by the ring‐opening polymerization of cyclic carbonate initiated with a trifunctional,poly(ethylene glycol)‐based surfactant

Amphiphilic, star‐shaped copolymers were synthesized by the ring‐opening polymerization of trimethylene carbonate initiated with a trifunctional, poly(ethylene glycol)‐based surfactant (polyoxyethylene sorbitan monolaurate) in the absence of any catalysts. The metal‐ and solvent‐free polymerization proceeded at 150 °C and afforded polyoxyethylene sorbitan monolaurate‐block‐poly(trimethylene carbonate) with number‐average molecular weights of 4500–11,900 in excellent yields. The copolymers successfully dispersed in a water/ethyl acetate (10/1 v/v) mixture, and the uniform suspension could contain a hydrophobic pigment and pyrene. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6633–6639, 2006     

Synthesis of new graft copolymers containing polyisobutylene by a combination of the 1,1‐diphenylethylene technique and cationic polymerization

The synthesis of macroinitiators for the cationic polymerization of isobutylene via radical polymerization is presented. The 1,1‐diphenylethylene system was used to obtain macroinitiators consisting of 4‐chloromethylstyrene and methyl methacrylate units. The resulting polymers were used for the cationic polymerization of isobutylene, yielding graft copolymers that were characterized by gel permeation chromatography and NMR. The dependence of the molar mass and polydispersity on the temperature and monomer concentration was studied. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3725–3733, 2002     

Polymer Cages as Universal Tools for the Precise Bottom‐Up Synthesis of Metal Nanoparticles

A template synthesis allows the preparation of monodisperse nanoparticles with high reproducibility and independent from self‐assembly requirements. Tailor‐made polymer cages were used for the preparation of nanoparticles, which were made of cross‐linked macromolecules with pendant thiol groups. Gold nanoparticles (AuNPs) were prepared in the polymer cages in situ, by using different amounts of cages versus gold. The polymer cages exhibited a certain capacity, below which the AuNPs could be grown with excellent control over the size and shape. Control experiments with a linear diblock copolymer showed a continuous increase in the AuNP size as the gold feed increased. This completely different behavior regarding the AuNP size evolution was attributed to the flexibility of the polymer chain depending on cross‐linking. Moreover, the polymer cages were suitable for the encapsulation of AgNPs, PdNPs, and PtNPs by the in situ method.     

Synthesis of poly(n‐hexyl isocyanate‐b‐N‐vinylpyrrolidone) block copolymers by the combination of anionic and nitroxide‐mediated radical polymerizations: Micellization properties in aqueous solutions

A combination of anionic and nitroxide‐mediated radical polymerizations (dual initiator) was employed for the synthesis of poly(n‐hexyl isocyanate‐b‐N‐vinylpyrrolidone) (PHIC‐b‐PNVP) block copolymers. The samples were characterized with a size exclusion chromatograph equipped with refractive‐index and light scattering detectors as well as ¹H NMR spectroscopy. Relatively good control over the molecular weights was achieved. However, rather broad molecular weight distributions were obtained. The micellar properties of the PHIC‐b‐PNVP block copolymers were studied in water, which is a selective solvent for the poly(N‐vinylpyrrolidone) blocks. Static and dynamic light scattering revealed the presence of equilibrium between the micelles and clusters. The clusters partially deaggregated with increasing temperature. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5719–5728, 2006     

Synthesis of nanocylinders consisting of graft block copolymers by the photo‐induced ATRP technique

Photoinduced atom transfer radical polymerizations (ATRP) of t‐butyl methacrylate (BMA) were carried out, initiated by model initiator benzyl N,N‐diethyldithiocarbamate (BDC) in the presence of CuCl/bipyridine (bpy) under UV irradiation. We performed the first‐order time‐conversion plots in this polymerization system, and the straight line in the semilogarithmic coordinates indicated a first‐order in the monomer. The molecular weight of poly(t‐butyl methacrylate) (PBMA) increased in direct proportion to monomer conversion. The molecular weight distribution (M_w/M_n) of PBMA was about 1.3. The initiator efficiency, f, was close to 1.0, which indicated that no side reactions occurred. A copper complex, CuCl/bpy, reversibly activated the dormant polymer chains via a N,N‐diethyldithiocarbamate (DC) transfer reaction such as Cu(DC)Cl/bpy, and it was dynamic equilibrium that was responsible for the controlled behavior of the polymerization of BMA. On the basis of this information, we established a preparation method of nanocylinders consisting of graft block copolymers by grafting from photoinduced ATRP of multifunctional polystyrene having DC pendant groups with vinyl monomers [first monomer, BMA; second monomer, styrene or methyl methcrylate (MMA)]. We have carried out the characterization of such nanocylinders in detail. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 63–70, 2005     

The use of a new,modified Dittmer–Lester spray reagent for phospholipid determination by the TLC image analysis technique

A new phospholipid‐specific spray reagent is described. A new phospholipid‐specific spray reagent, which is a modification of the Dittmer–Lester reagent, is described in authors' studies. The difference between these two reagents is in the addition of tin (II) chloride to the proposed spray reagent. The use of the described spray reagent together with an image analysis technique allows not only for qualitative, but also for quantitative, determination of major phospholipid classes. Separation of phosphatidylserine (PS), phosphatidylethanolamine (PE) and phosphatidylcholine (PC) was conducted on an HPTLC plate with a mixture of chloroform, methanol and 25% ammonia solution in a volume ratio of 65:25:4 as mobile phase. The calibration curves were linear in the ranges of 5.0–25.0, 1.5–15.0 and 1.0–20.0 µg/spot for PC, PS and PE, respectively. The use of the new spray reagent resulted also in lower limits of detection than the standard molybdenum method for the investigated phospholipids. The proposed method was used to determine the amount of PS in the dietary supplement ‘Session’, and of PS, PE and PC in biological samples, with good results. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,characterization of layered double hydroxide‐poly(methylmethacrylate) graft copolymers via activators regenerated by electron transfer for atom transfer radical polymerization and its effect on the performance of poly(lactic acid)

Layered double hydroxide‐poly(methylmethacrylate) (LDH‐PMMA) graft copolymers were prepared via activators regenerated by electron transfer for atom transfer radical polymerization. The results showed that the hydrophobicity of LDH‐PMMA was improved by the incorporation of hydrophilic groups. Moreover, poly(lactic acid) (PLA)/LDH‐PMMA nanocomposites were prepared by melt blending to enhance the performances of PLA. The crystallization and mechanical properties of the PLA/LDH‐PMMA nanocomposites were studied by differential scanning calorimetry, tensile testing, and polarized optical microscopy, respectively. Results of mechanical testing showed that the tensile strength, elongation at break, and impact strength of PLA/LDH‐PMMA nanocomposites were increased by 5.64%, 37.95%, and 49.70%, respectively, compared with PLA. The differential scanning calorimetry results indicated that LDH‐PMMA eliminated the cold crystallization of PLA matrix and improved the crystallinity of PLA by 37.26%. The polarized optical microscopy of PLA/LDH‐PMMA nanocomposites demonstrated that LDH‐PMMA increased the crystallization rate of PLA. It was also found that the rheological behaviors of the PLA nanocomposites were significantly enhanced. Based on these results, a new choice for modified LDHs was provided and used as a nucleating agent to improve the properties of PLA.