Controlled drug release studies of atenolol using differently sulfonated acryloxyacetophenone and methyl methacrylate copolymer resins as drug carriers

2-Acryloxyacetophenone(AAP) was prepared and subjected to suspension polymerization with methyl methacrylate(MMA) using azobisisobutyronitrile(AIBN) as free radical initiator.The differently sulfonated AAP-MMA cross-linked copolymer cationic exchange resins were prepared by sulfonation with concentrated sulphuric acid at 70 °C.Several characteristics of the prepared resins were evaluated,i.e.FTIR,the ion-exchange capacity(IEC),thermo gravimetric analysis(TGA),particle size distribution and microscopic morphology.The resin characteristics were altered with degree of sulfonation,providing that differently sulfonated resins could be prepared.The behavior of atenolol(ATL) loading and in vitro release in the USP stimulated gastric and intestinal fluids of the obtained resins were evaluated.The drug loaded in the resin increased with increasing degree of sulfonation and hence the drug binding site in resin employed.The drug release was lower from the resins with higher content of sulfonic group due to the increase in the diffusive path depth.The drug release was a little lower in stimulated gastric fluid(SGF) than in stimulated intestinal fluids(SIF).The basic groups,ionized to a little greater extent in SGF and preferred binding with the resin rather than releasing.Hence,the differently sulfonated resins could be utilized as novel carriers for drug delivery.     

Optoelectronic properties of fluorene-co-4,7-difuran-2,1,3-benzothiadiazole copolymers

Light-emitting and photovoltaic properties of copolymers(PFO-FBT) based on 9,9-dioctylfluorene and 4,7-difuran-2,1,3-benzothiadiazole(FBT) units were investigated.The copolymers show two absorbance peaks at around 382 nm and 530 nm,respectively.The relative absorbance at around 530 nm of the PFO-FBT copolymers increases with the increasing FBT content.The EL emissions are red-shifted from 611 nm to 702 nm by increasing the FBT content in the copolymer.The highest EL external quantum efficiency ach...     

CO2-sensitive amphiphilic triblock copolymer self-assembly morphology transition and accelerating drug release from polymeric vesicle

A series of triblock copolymers,containing a CO2-switchable block poly(2-(dimethylamino)ethyl methacrylate) (PDM) block and two symmetrical hydrophilic blocks polyacrylamide (PAM),were synthesized using atom transfer radical polymerization (ATRP) method.The pH and conductivity tests showed that the triblock copolymer exhibited switchable responsiveness to CO2,i.e.a relatively low conductivity of solution could be switched on and off by bubbling and removing of CO2,and the triblock copolymer aqueous solution displayed a CO2-switchable viscosity variation.The changes were all attributed to protonation of tertiary amine groups in PDM blocks and proven by 1H-NMR.Cryogenic transmission electron microscopy and dynamic light scattering characterization demonstrated that the viscosity variation was the result of a unilamellar vesicle-network aggregate structure transition.The release of rhodamine B from the vesicles with and without CO2 stimuli showed the potential application in drug delivery domains;after CO2 bubbling,the drug release rate could be accelerated.Finally,reasonable mechanism of CO2-switchable morphology changes and CO2-induced drug release was proposed.     

铁系亚胺基吡啶复配催化乙烯原位共聚产物的表征

Branched polyethylene from ethylene as single monomer was prepared by the tandem catalyst system of {2-[2-Me C6 H4 N=Me)]2 C5H3N} FeCl2 (1) and {2,6-[1-(2,6-Me2-4-Br-C6H4N=(Me)]2C5H3N} FeCl2 (2) activated with methylaluminoxane (MAO) . The products of polymerization were characterized by DSC, GPC and ^13C-NMR. The results revealed that the copolymer produced by in situ copolymerization of ethylene was a mixture of branched polyethylene and α-olefin. The content of α-olefin in the mixture was increased with increasing the molar ratio of catalysts 1/2. The MWD paramelers of polyethylene and copolymer were 28.6 and 7.9, respectively. ^13C-NMR spectra showed that there were ethyl groups, butyl groups and long chain alkyl groups in the copolymer. The average degree of branching of such branched polyethylene was less than 5C/1000C.     

RANDOM COPOLYMER OF PROPYLENE OXIDE AND ETHYLENE OXIDE PREPARED BY DOUBLE METAL CYANIDE COMPLEX CATALYST

Copolymerization of propylene oxide (PO) and ethylene oxide (EO) using double metal cyanide (DMC) complexas the catalyst was carried out. The structure of random copolymers was confirmed by ~(13)C-NMR and IR spectra. ~1H-NMRanalysis shows that the EO content in the copolymer is the same as that in the initial monomer feed. Moderate molecularweight copolymers with various EO content were obtained and their values of molecular weigh distribution (MWD) fell inthe range of 1.21-1.55. It was found that the molecular weight of copolymers is controlled by the mass ratio of EO + PO toinitiator moles used. The reaction rate as well as polymer yield decrease with increasing EO content in the feed composition.     

Hydrophilicity Modification of Addition-cured Room Temperature Vulcanization Silicone Rubber

Allyl terminated polyether was used to improve the hydrophilicity of addition-cured room temperature vulcanization silicone rubber. With the increasing of the polyether, both the hydrophilicity and water absorbed of the vulcanizates were increased. The mechanical properties were also improved by adding the polyether. The result showed that 1.5wt% of the polyether provided the silicone rubber with proper hydrophilicity.     

PREPARATION OF POLYMER DISPERSED LIQUID CRYSTALS USING PHOTOPOLYMERIZATION

2-Hydroxycthyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electro-optical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser andscanning electron microscopy, respectively. With increasing E7 content in the copolymer, droplet size increased, thresholdvoltage decreased,     

SYNTHESES OF STYRENE-METHYL METHACRYLATE BLOCK COPOLYMER BY POLYAZOAMIDE AS INITIATOR

Polyazoamide(PAA) was used as initiator to prepare block copolymer P(MMA-b-St) byfree radical polymerization. The fraction of block copolymer was about 50%. The structureof the block-copolymer was characterized by IR and the results of ~1H-NMR and GPCshowed that the content of the block and the molecular weight (M_w) of the prepolymerand block copolymer could be controlled by varying the mol ratio of styrene/PAA andMMA/prepolymer. DSC and TEM results revealed that the block copolymer has twoseparated glass transition temperatures and phase separation within the domain structure.     

Photo cross-linked biodegradable hydrogels for enhanced vancomycin loading and sustained release

A series of biodegradable hydrogels based on dextran and poly（L-glutamic acid） were fabricated for effective vancomycin loading and release. The preparation of hydrogels was simply achieved by photo cross-linking of methacrylated dextran and poly（L-glutamic acid）-g-hydroxyethyl methacrylate （PGH） in the presence of photoinitiator 12959. The structures of hydrogels were characterized by FTIR and SEM. The swelling and enzymatic degradation behaviors of hydrogels were examined to be dependent on the poly（L-glutamic acid） content in the hydrogels. The higher content of poly（L-glutamic acid） in the gel, the higher swelling ratio and quicker degradation were observed. More interestingly, the hydrogel with higher PGH ratio showed higher vancomycin （VCM） loading content, which might be due to the electrostatic interaction between carboxylate groups in hydrogel and ammonium group of VCM. In vitro drug release from the VCM-loaded hydrogels in aqueous solution exhibited sustained release of VCM up to 72 h, while the in vitro antibacterial test based on the VCM-loaded hydrogel showed an efficient Methicillin-Resistant S. aureus （MRSA） inhibition extending out to 7 days. These results demonstrated that the biodegradable hydrogels which formed by in situ photo-cross linking would be promising as scaffolds or coatings for local antibacterial drug release in tissue engineering.     

Redox-responsive polymer prodrug/AgNPs hybrid nanoparticles for drug delivery

The redox-responsive hybrid nanoparticles of P(MACPTS-co-MAGP)@AgNPs is developed for drug delivery and fluorescence monitoring of the drug release by applying the NSET-based strategy.     

Comparison of drug delivery properties of PEG-<Emphasis Type="Italic">b</Emphasis>-pdhpc micelles with different compositions

An anti-tumor drug doxorubicin was encapsulated in micelles of poly（ethylene glycol）-b-poly（2,2-dihydroxyl-methyl propylene carbonate）（PEG-b-PDHPC） diblock copolymers.The morphology of both blank micelles and drug loaded micelles was characterized by TEM.The in vitro drug release profiles of micelles were investigated.The cytotoxicity of the micelles was evaluated by incubating with Hela tumor cells and 3T3 fibroblasts.The drug loaded micelles were co-cultured with HepG2 cells to evaluate the in vitro anti-tumor efficacies.The results showed that the mean sizes of both micelles with different copolymer compositions increased after being loaded with drugs.The drug release rate of PEG₄₅-b-PDHPC₃₄ micelles was faster than that of mPEG₁₁₄-b-PDHPC₂₆,micelles.Both of the two block copolymers were non-toxic.The confocal laser scanning microscopy and flow cytometry results showed that both the drug loaded micelles could be internalized efficiently in HepG2 cells.The PEG₄₅-b-PDHPC₃₄ micelles exhibited higher anti-tumor activity comparing to mPEG₁₁₄-b-PDHPC₂₆ micelles.     

Temperature and pH Dually-responsive Poly(β-amino ester) Nanoparticles for Drug Delivery

Stimuli-responsive polymers have undoubtedly been of great interest in the past decades due to a variety of their potential applications in biomedical territory. However, their non-degradability limits their in vivo applications. Herein, we report a novel pH and temperature dual-stimuli responsive-poly(β-amino ester). The pH/temperature sensitivities are interrelated and can be easily tuned by changing PEG-diacrylate chain length and the percentage of biamines in the feed ratio. These dual-responsive polymers are very useful in drug delivery. Reaction of methyl ether poly(ethylene glycol)(MPEG) and poly(β-amino ester) resulted in an amphiphilic MPEG-PBAE block copolymer which could form nanoparticles by selfassembly. A hydrophobic drug(DOX) was loaded in the self-assembled nanoparticles at low temperature without using organic solvents. The loaded drug was released very slowly and steadily at 37 ℃ under physiological conditions(p H 7.4), but rapidly released from the micelles in weakly acidic environments(pH 6.4 and 5.0) for intracellular drug release. Thus, these poly(β-amino ester) polymers constitute ideal drug carriers since their thermal sensitivity allows the drug loadings without using organic solvent and their pH sensitivity permits fast intracellular drug release.     

IONIC CONDUCTIVITY IN THE COMPLEXES OF COMB-SHAPED POLYETHER WITH LITHIUM AROMATIC SULFONATE

Complexes of comb-shaped polyether and lithium aromatic sulfonates bearing different negative charge number were prepared by in situ thermal polymerization. Their conductivity depends deeply on salt content, ambient temperature and negative charge number of the added salts. Results show that anions can be partly immobilized by increasing their negative charges at lower temperature. Against discharge time the short circuit current of the battery (Li/complex film/Li_x V_3O_8) is stabilized by increasing the anionic charge number of the complex.     

Structures and oxygen storage/release capacities of Ce_xZr_(1-x)O_2: Effects of Zr content and preparation method

Ceria-zirconia solid solution has been prepared by the urea grind combustion and citric acid sol-gel methods for catalytic applications as oxygen storage/release materials in this study. The properties and oxygen storage/release capacities of samples with different Zr contents were characterized and evaluated by X-ray diffraction(XRD), N_2 adsorption, scanning electron microscopy(SEM), Raman spectroscopy, and insitu CO–CO_2 looping test. The results demonstrate that the samples prepared by two methods are all of excellent lattice [O] release/storage properties and maintain good long-term cycle stability. But the preparation method significantly impacts the homogeneity of samples related to their redox properties and the content of Zr over 20%, which greatly changed the properties of ceria-zirconia solid solutions and caused their changing of crystalline symmetry from cubic to tetragonal. The samples prepared by citric acid solgel method are of more homogeneous particle sizes and higher specific surface areas than that by urea grind combustion method, which is benefit to the oxygen release rather than oxygen storage. The bulk oxygen amount migrated to surface increases with the increasing Zr content, however, the amount of lattice oxygen migration decreases when Zr content is over 20%. When Zr content is 20%, the differences of storage/release capacities from two different preparation methods are reduced at high temperature in the long-term loop reaction.     

SYNTHESIS AND CHARACTERIZATION OF COPOLYMER OF 2,5-BIS[（4-METHOXYPHENYL）OXYCARBONYL]STYRENE AND STYRENE WITH HIGH MOLECULAR WEIGHT

The random copolymers of styrene and 2,5-bis[(4-methoxyphenyloxycarbonyl)styrene] (MPCS) with different copolymerization ratio were synthesized by conventional free radical polymerization. The copolymer having high molecular weight was experimentally elucidated using a combination of proton nuclear magnetic resonance spectroscopy and gel permeation chromatography. The liquid crystalline behavior of the copolymer was studied using differential scanning calorimetry, X-ray diffractometry and polarized optical microscopy. It was found that the liquid crystalline behavior was dependent on the content of styrene. Experimental results show that the copolymer could turn into a liquid crystalline phase at about 180℃ when the content of styrene was less than 20%. The mechanical properties of the copolymer were also studied. Preliminary results indicate that the tensile strength decreases while the tensile modulus increases as the content of MPCS is increased.     

Synthesis and characterization of random or gradient butadiene-p-methylstyrene copolymers via anionic polymerization

Copolymers of 1,3-butadiene and p-methylstyrene （p-MS） were synthesized via anionic polymerization. A benzophenone-potassium complex was added to tune the reactivity ratio of the two monomers, leading to random and gradient composition alonglthe copolymer chain. The overall composition and microstructure could be controlled and well characterized by GPC and H-NMR. The p-MS was distributed from gradient to random with increasing the content of the benzophenone-potassium complex, and the 1,2-microstrucmre in the polybutadiene sequence increased at the same time. The hydrogenation of the copolymer of 1,3-butadiene and p-MS resulted in the corresponding saturated copolymer with well- defined structure and narrow molecular weight distribution.     

聚肽接枝共聚物的自组装行为研究

Polymeric micelles of poly(γ-benzyl L-glutamate)(PBLG)-poly(ethylene oxide)(PEO) graft copolymer were prepared by the dialysis method in deionized water. Fluorescence spectroscopy, nuclear magnetic resonance(NMR) and transmission electron microscope(TEM) were used for the investigation of the self-assembly of PBLG-PEO graft copolymer. Fluorescence spectrosco0y measurements suggest that PBLG-PEO graft copolymer associates to form polymeric micelles in water. ^1H NMR measurements further prove that in aqueous medium PBLG-PEO graft copolymer could assemble into polymeric micelles with PBLG segments as the hydrophobic inner core and PEO segments as the hydrophilic shell. The results of the TEM observations show that the polymeric micelles of PBLG-PEO graft copolymer are almost spindly shaped, which are different from the morphology of the spherical micelles formed by PBLG-PEO block copolymer. Polymeric micelles formed by polypeptide copolymer have potential application as drug carrier in controlled-release delivery system.     

STUDIES ON POLY(ETHYLENE TEREPHTHA LATE)-POLY(TETRAMETHYLENE ETHER) MULTIBLOCK COPOLYMER.Ⅰ.COMPOSITIONAL HOMOGENEITY

The compositional homogeneity of a poly (ethylene terephthalate)-poly (tetramethylene ether) multiblock copolymer sample with low content of hard segment was examined by GPC, TLC, and solubility method. The copolymer sample was found to have a uniform composition as a function of elution volume over the major portion of sample from GPC method. However within one elution fraction, the copolymer chains, although having the same hydrodynamic volume, may have some difference in composition. Two fractions with different composition were obtained by precipitation in ethanol. Some low molar mass copolymers were also separated by a TLC technique from the copolymer sample.     

Preparation of sulphonate-containing polymer particles <Emphasis Type="Italic">via</Emphasis> semi-continuous emulsion copolymerizaion of styrene and sodium styrene sulphonate

Submicron-sized P(St-NaSS) latexes were prepared via a semi-continuous emulsion copolymerization of styrene (St) and sodium styrene sulphonate(NaSS) in the presence of anionic surfactant,in which NaSS aqueous solution and St were separately dropwise charged into the polymerization system at the same time.The hydrodynamic diameter of the latex particles was measured by dynamic light scattering(DSL) method,and the NaSS unit content of the purified copolymer by water extraction was calculated based on the elementary analysis.Results showed that the copolymerization could be performed smoothly with the monomer conversion more than 96%in the absence of crosslinker,and PNaSS homopolymer could be removed from the latex product by water extraction for 28 h.The weight loss in the water extraction tended to decrease and the NaSS unit content of the purified copolymer tended to increase with the increase of monomer feeding time, and both of them increased with the increase of NaSS/St mole ratio in the charge.The introduction of divinyl benzene (DVB) could decrease the weight loss in the water extraction and increase the NaSS unit content of the purified copolymer. When 25/75 mole ratio of NaSS/St and 11 mol%DVB of total NaSS and St were used in the recipe,and the monomer feeding time was 3 h in copolymerization,the NaSS unit content of the purified copolymer reached 7.31 mol%.     

Nucleation and crystallization of H-shaped (PS)2PEG(PS)2 block copolymers

<正>A series of H-shaped(PS)_2PEG(PS)_2 block copolymers with different PS chain lengths were prepared.The influence of different confinements active on the crystallization and self-nucleation(SN) behavior of the PEG blocks was investigated by differential scanning calorimetry(DSC).When the content of the crystalline block was high,a classical SN behavior was obtained.The block copolymer with PEG content of 49%(by weight) showed a classical SN behavior with a narrow self-nucleation domain and had bimodal crystallization exotherms.When the PEG dispersed as separated microdomains in the block copolymer,the self-nucleation domain disappeared and only annealing was observed.