Water‐soluble star‐like poly(vinyl alcohol)/C60 and poly{[poly(ethylene glycol) acrylate]‐co‐(vinyl acetate)}/C60 nanohybrids are prepared by grafting macroradicals onto C60 and are assessed as photosensitizers for photodynamic therapy. The photophysical and biological properties of both nanohybrids highlight key characteristics influencing their overall efficiency. The macromolecular structure (linear/graft) and nature (presence/absence of hydroxyl groups) of the polymeric arms respectively impact the photodynamic activity and the stealthiness of the nanohybrids. The advantages of both nanohybrids are encountered in a third one, poly[(N‐vinylpyrrolidone)‐co‐(vinyl acetate)]/C60, which has linear grafts without hydroxyl groups, and shows a better photodynamic activity.
Summary: Poly(vinyl acetate) chains end‐capped by a Co(acac)2 complex [PVAc‐Co(acac)2] were prepared by bulk cobalt‐mediated radical polymerization (CMRP) of vinyl acetate and used for grafting fullerene (C60) with four PVAc arms at low temperature (30 °C). A photoactive water‐soluble poly(vinyl alcohol)/C60 nanohybrid was then prepared by hydrolysis of the PVAc arms of the nanohybrid. Because of photoactivity and very low cytotoxicity, this type of water‐soluble nanohybrid is very promising for the photodynamic cancer therapy.
Strategy for the preparation of PVAc/C60 nanohybrid and hydrolysis of PVAc/C60 nanohybrid into PVOH/C60 nanohybrid. 相似文献
Summary: Poly(vinyl acetate) macroinitiators end‐capped by a Co(acac)2 complex (PVAc–Co(acac)2), prepared in bulk by cobalt‐mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high‐molecular‐weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.‐% are prepared within unusually short reaction times (∼1 h) at low temperatures (0–30 °C).
SEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion). 相似文献
Summary: we have investigated by DSC and FTIR the miscibility and phase behaviour of binary and ternary blends of different ratios of poly(styrene-co-methacrylic acid) containing 15 mol% of methacrylic acid (SMA15) with poly(styrene-co-N,N-dimethylacrylamide) containing 17 mol% of N,N,-dimethylacrylamide (SAD-17) and poly(styrene- co-4-vinylpyridine) containing 15 mol% of 4-vinylpyridine. SMA15 is miscible with both SAD17 and S4VP15 and interacts more strongly with S4VP15 than with SAD17 as evidenced by the positive deviations from linear average line observed with these blends and the appearance of new bands in the 1800–1550 cm−1 region. This behaviour is known as ΔK effect. The FTIR study confirms that though the specific intermolecular interactions that occurred with each pair of the SMA15/S4VP15 and SMA15/SAD17 binary components are of different strength, they still exist in the ternary blend. Even though the three binary polymer pairs are individually miscible, the ternary system of SMA15/S4VP15/SAD17 exhibits only partial miscibility with small loop of immiscibility due to a significant ΔK effect. These results obtained by DSC and FTIR are in a fair agreement with theoretical prediction applying the Painter-Coleman association model. 相似文献
Poly(ethylene oxide) (PEO)/LiClO4/poly(vinyl acetate) (PVAc) and PEO/LiClO4/poly(vinyl pyrrolidone) (PVP) complexes were prepared with various weight ratios of PVAc and PVP to PEO. The conductivity (σ) of the PEO/LiClO4 complex was increased in a nonlinear fashion by the presence of up to 60 wt% PVAc. PEO/LiClO4/PVAc complexes with weight percents of PVAc greater than 60 had σ's less than that of PEO/LiClO4. The σ of PEO/LiClO4 was decreased by the presence of any PVP. 相似文献
The crystallization process of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA)and PEO/poly(vinyl acetate) (PVAc) blends has been characterized by Fourier Transform Infrared(FTIR) spectra in conjunction with Differential Scanning Calorimeter (DSC) measurements. Thecrystallinity of PEO varies consistently with PEO content in PEO/PVAc blends and the PEO/PMMAblends containing 50 wt% or less PMMA. For the PEO/PMMA blends containing 60 wt% ormore PMMA, the crystallinity of PEO decreases more than PEO content but develops with crystal-lization time. These results can be explained in terms of difference between the crystallization tem-perature (T_c) and glass transition temperature (T_g) of the blends as a function of content of amorphouscomponent. 相似文献
A series of amphiphilic graft copolymers of poly (vinylidene fluoride‐co‐chlorotrifluoroethylene)‐g‐poly(2‐vinyl pyridine), P (VDF‐co‐CTFE)‐g‐P2VP, with different degrees of P2VP grafting (from 26.3 to 45.6 wt%) was synthesized via one‐pot atom transfer radical polymerization (ATRP). The amphiphilic properties of P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers allowed itself to self‐assemble into nanoscale structures. P (VDF‐co‐CTFE)‐g‐P2VP graft copolymers were introduced into neat P (VDF‐co‐CTFE) as additives to form blending membranes. When two different solvents, N‐methyl‐2‐pyrrolidone (NMP) and dimethylformamide (DMF), were used, specific organized crystalline structures were observed only in the NMP systems. P (VDF‐co‐CTFE)‐g‐P2VP played a pivotal role in controlling the morphology and pore structure of membranes. The water flux of the membranes increased from 57.2 to 310.1 L m?2 h?1 bar?1 with an increase in the PVDF‐co‐CTFE‐g‐P2VP loading (from 0 to 30 wt%) due to increased porosity and hydrophilicity. The flux recovery ratio (FRR) increased from 67.03% to 87.18%, and the irreversible fouling (Rir) decreased from 32.97% to 12.82%. Moreover, the pure gas permeance of the membranes with respect to N2 was as high as 6.2 × 104 GPU (1 GPU = 10–6 cm3[STP]/[s cm2 cmHg]), indicating their possible use as a porous polymer support for gas separation applications. 相似文献
Summary: A multistep synthetic procedure for preparing novel C60‐anchored two‐armed poly(tert‐butyl acrylate) was developed. First, two‐armed poly(tert‐butyl acrylate) bearing a malonate ester core with well‐controlled molecular weight was synthesized through atom transfer radical polymerization. The effective Bingel reaction between C60 and the well‐defined polymer was then carried out to yield C60‐anchored polymer. GPC, 1H NMR, and UV‐vis spectroscopy indicated that the C60‐anchored polymer was a monosubstituted and ‘closed’ 6,6‐ring‐bridged methanofullerene derivative.
Schematic of a novel C60‐anchored two‐armed polymer. 相似文献
Fullerene (C60), the third carbon allotrope, has shown great potential in photoelectric materials and drug delivery. However, the low solubility of C60 in polar solvents, especially in water, is the major limiting factor for further applications. The use of ultrasound and amphiphilic block copolymers, poly(ethylene glycol)-block-poly(4-vinylpyridine) (PEG-b-P4VP), helped to disperse C60 in acidic aqueous solutions. As characterized by dynamic light scattering, transmission electron microscopy, and UV-visible spectroscopy, the C60 colloids had a core-shell structure with C60 aggregated in the micellar cores. The photosensitized generation of singlet oxygen using C60-bound polymer micelle was confirmed by the iodide method. More importantly, C60 and metalloporphyrin complexes could be synthesized by the self-assembly between PEG-b-P4VP/C60 micelle and metalloporphyrin. The stability of metalloporphyrin increased in the presence of the PEG-b-P4VP/C60 micelle. This study provides a method for the solubilization of C60 with many potential applications in biomedicals and photovoltaics. 相似文献
Composites of a polyindole (PIN) and poly(vinyl acetate) (PVAc) were prepared chemically using FeCl3 as an oxidant agent in anhydrous media. The composite compositions were altered by varying the indole monomer during preparation. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), stress‐strain experiments and conductivity measurements. Moreover, the film of PVAc and PIN/PVAc composites were prepared by casting on glass Petri dishes to examine their stress‐strain properties. PIN/PVAc composites are thermally more stable than PIN. It was found that the conductivities of PIN/PVAc composites depend on the indole content in the composites. 相似文献