二醋酸纤维素 -聚乙二醇接枝共聚物的核磁共振表征

用^1H NMR和^13C NMR核磁共振技术研究了二醋酸纤维素和聚乙二醇的接枝反应,并确定了^1H NMR和^13C NMR谱中各谱峰的归属,为证明二醋酸纤维素和聚乙二醇的接枝反应提供了依据。     

New Possibilities of the Acetosulfation of Cellulose

Regioselectively substituted cellulose sulfates in C2/3-, C2/6-, or C6-position of the anhydroglucose unit are accessible by certain synthesis routes. Thereby, products with different properties and various application areas are resulted. Important characteristics of cellulose sulfates regarding their applications are solubility (e.g. in water), rheological behavior, different interaction with low or high molecular cations, thermo reversible gel formation, enzymatic degradability, anticoagulant and antiviral activity. In C6-position substituted cellulose sulfates can be synthesized in principle by acetosulfation. The acetosulfation is a quasi-homogeneous synthesis proceeding under gradually dissolution of the cellulose by using different reactivity of the primary and secondary OH-groups as soon as converting cellulose acetate sulfates. After precipitation of the polymer the acetyl groups are cleaved in alkaline solution. The focus of our study was firstly the investigation of the acetosulfation in different polar aprotic solvents by various sulfating and acetylating agents. In general it should be investigated if C6 substituted cellulose sulfates can be obtained by acetosulfation with different solvents and agents. The products were characterized by ¹³C-NMR and Raman spectroscopy.     

Polymeric membranes based on cellulose acetate loaded with candle soot nanoparticles for water desalination

This study is concerned with modifying cellulose acetate (CA)/polyethylene glycol (PEG) membranes prepared via phase inversion technique in the presence of carbon nanoparticles; candle soot (CS) resulting from combusted candle. CS nanoparticles were analyzed via Fourier transform infrared spectroscopy and transmission electron microscopy. The developed membranes were characterized for their surface morphology, mechanical properties as well as thermal stability. CS nanoparticles contributed in improving the salt rejection % with a slight reduction in the water flux behavior. Employing the annealed cellulose acetate/polyethylene glycol membranes loaded with candle soot nanoparticles provides an adequate approach towards water desalination implementations.     

Interactions of ionic liquids with polysaccharides 9. Hydroxyalkylation of cellulose without additional inorganic bases

Water-soluble hydroxyalkyl cellulose with a molar degree of substitution of up to 2.79 was prepared under completely homogeneous reaction conditions in various ionic liquids without addition of inorganic bases. In acetate containing solvents the IL acts as a catalyst. The substitution patterns of the cellulose ethers were analyzed by ¹³C NMR spectroscopy, ¹H NMR spectroscopy after peracetylation and GLC/MS after permethylation and depolymerization. A diminished tendency towards the formation of side chains compared to heterogeneously prepared hydroxyalkyl celluloses in the presence of inorganic bases was found.     

Preparation and pore-size control of hydrophilic monodispersed polymer microspheres for size-exclusive separation of biomolecules by the SPG membrane emulsification technique

This paper describes an experiment directed toward the preparation of monodispersed porous polymer microspheres with a diameter of ca. 50 m, which is applicable to the chromatographic separation of biomolecules such as proteins and peptides by size exclusion. Fairly monodispersed polymer microspheres were successfully prepared by suspension copolymerization of polyethylene glycol monomethacrylate and ethylene glycol dimethacrylate as monomer and cross-linker, respectively. Monodispersed O/W emulsion was prepared by the SPG membrane emulsification technique, and was used in the subsequent droplet-swelling process in which monodispersed seed droplets were swollen by adsorbing the secondary emulsion droplets. The effects of the organic diluent in suspension polymerization and comonomer on the porous structure of the polymer microspheres were investigated by scanning electron microscopy and mercury-intrusion porosimetry, and the separation performances of polystyrene, polyethylene glycol, and various biomolecules by size-exclusion chromatography. As a result, it was evident that benzene, 1-butanol, and butyl acetate worked as nonsolvents for the polymer prepared in this study, and that polymer microspheres prepared with these solvents had larger pores. Size-exclusion chromatography revealed that the exclusive limiting molecular weight was 1.9×10⁵ when polystyrene was used as a standard polymer, and 3.5×10⁴ when polyethylene glycol was used as a standard polymer. Furthermore, we confirmed that the monodispersed polymer microspheres with defined pores clearly separated the six representative kinds of biomolecules with molecular weights ranging from 75 to 6.4×10⁵.     

Biodegradable Cellulose Graft Copolymers. I. Condensation-Type Graft Reactions

The synthesis of cellulose graft copolymers using condensation reactions to graft onto the cellulose backbone is described. Cellulose acetate (D.S. 2.27) was grafted with MDI and TDI. The cellulose acetate-MDI copolymer was further reacted with hydroxy-terminated poly(butadiene-styrene) copolymer and polyethylene glycol. Grafting was confirmed by Pmr and IR spectroscopy. The copolymers were easily deacetylated with NaOMe. The deacetylated products were readily degraded by cellulysin, faster than cellulose itself.     

Monomeric dioxouranium(VI), chromium(III), cobalt(II), nickel(II) and copper(II) complexes with primary cellulose acetate (PCA)

Monomeric UO ₂ ²⁺ , Cr^III, CO^II, Ni^II and Cu^II complexes with primary cellulose acetate (PCA) have been prepared and characterized. Infrared,¹H NMR, UV/visible spectroscopy, elemental analysis, therniogravimetry, conductance and magnetic measurements were used to assign the mode of coordination in the isolated species. The investigation revealed that PCA exhibits octahedral coordination with Cr^III, Co^II, Ni^II and a square planar form with Cu^II whereas the UO₂ moiety is virtually linear. PCA acts as a neutral bidentate chelating agent via the two oxygen atoms of the vicinal ester groups in the secondary positions forming a five-membered chelate ring. A comparative study between chelates of PCA and those previously prepared with secondary cellulose acetate (SCA) has been undertaken.     

Preparations of regioselectively methylated cellulose acetates and their 1H and 13C NMR spectroscopic analyses

Seven possible regioselectively methylated cellulose acetates (RS‐MCAs)—2,3,6‐tri‐O‐methyl cellulose acetate, 3,6‐di‐O‐methyl cellulose acetate, 2,6‐di‐O‐methyl cellulose acetate, 2,3‐di‐O‐methyl cellulose acetate, 6‐O‐methyl cellulose acetate, 3‐O‐methyl cellulose acetate, and 2‐O‐methyl cellulose acetate—were prepared for the first time from chemically synthesized cellulose derivatives obtained by cationic ring‐opening polymerization and then were analyzed by ¹H and ¹³C NMR spectroscopy. The chemical shifts of ring protons and carbons were influenced by substituent groups (methyl or acetyl) and clearly reflected the pattern of substituent distribution in anhydroglucose units. These data may conveniently be used for the determination of the substituent distribution of methyl cellulose. The synthesized RS‐MCAs also may be used for the elucidation of the structure–property relationship. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4167–4179, 2002     

Regularities of formation of emboli of liquid polymer solutions in aqueous medium

Work on creating the basis for embolic compositions for the treatment of a wide range of pathologies of various organs was conducted. This basis is a solution of a biocompatible water-insoluble polymer in a biocompatible water-soluble solvent. Formation of the embolus in such an aqueous medium takes place in the transition of the solvent into the aqueous phase and the formation of a solid polymer clot occluding a blood vessel. Criteria for selection of the polymer and the solvent for the basis were formulated, and a number of polymers and solvents that meet these criteria were selected for further research. Research on the solubility of the selected polymers in solvents was carried out, and the rheoviscometric characteristics of polymer solutions, as well as parameters of solid emboli formation of polymer solutions in aqueous media, were found. The solution of cellulose acetate plasticized with OPADRY CA 500F190000 polyethylene glycol in dimethylsulfoxide with concentration of no less than 60 g/L was recognized as optimal for further studies.     

Biodegradable brushlike graft polymers. I. Polymerization of ϵ‐caprolactone onto water‐soluble hydroxypropyl cellulose as the backbone by the protection of the trimethylsilyl group

After the protection of partial hydroxyl groups with trimethylsilyl (TMS) groups, hydroxypropyl cellulose becomes soluble in organic solvents, and the number of hydroxyl groups as initiating groups can be controlled. As a result, a new brushlike graft poly(?‐caprolactone) can be prepared with hydroxypropyl cellulose as the backbone polymer by homogeneous ring‐opening graft polymerization and deprotection. The protection and deprotection of the TMS group during the entire procedure were carefully monitored with Fourier transform infrared (FTIR) and NMR, and the final graft copolymers were characterized with FTIR, ¹H NMR, ¹³C NMR, gel permeation chromatography, and differential scanning calorimetry. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 273–280, 2003     

聚氧乙烯交联网络-硫氰化钠络合体系离子电导的研究

合成了甲基丙烯酸聚氧乙烯酯大分子单体,其中含有少量双端酯化的单体。大分子单体经热交联,形成交联网络型聚氧乙烯,其与硫氰化钠形成的络合物的室温电导率较同类线型聚合物高二个数量级以上(～10^-5Ω^-1cm^-1/298K)。红外光谱表明:交联网络含较高的非晶成份。不同络合溶剂对形成的络合物聚集态有明显影响;络合盐浓度也对络合物结晶性有影响。     

Cellulose acetate graft copolymers with nano-structured architectures: Synthesis and characterization

Cellulose acetate is a very good film-forming polymer with major applications in cigarette filters, photographic films, cosmetics and pharmaceutics formulations and membrane separation processes. Nevertheless, its rigidity and relative hydrophobic character can be limiting drawbacks for some applications. In this work, new cellulose acetate materials with highly flexible and hydrophilic grafts were obtained with different hydrophilic/hydrophobic balances. Cellulose acetate was grafted with methyl diethylene glycol methacrylate (MDEGMA) from brominated macroinitiators by atom transfer radical polymerization (ATRP) in two steps. The first step consisted of introducing ATRP initiator groups on cellulose acetate by reacting hydroxyl side groups with 2-bromoisobutyryl bromide. A preliminary study was then carried out to determine the experimental conditions for the controlled ATRP of MDEGMA homopolymerization in a solvent (cyclopentanone) compatible with cellulose acetate grafting. In these conditions, the MDEGMA homopolymerization followed Hanns Fischer’s kinetics model accounting for the radical persistent effect. The ATRP grafting was then investigated for two cellulose acetate macroinitiators differing in the number of their ATRP initiator groups. Two families of graft copolymers with nano-structured architectures were obtained. The first family corresponded to copolymers with a high number of short grafts. The copolymers of the second family had almost the same graft weight fractions but a small number of long grafts. The morphology of the graft copolymers was then investigated by synchrotron X-ray scattering. The most informative results showed that the phase segregation depended upon the number and length of the poly(MDEGMA) grafts. The copolymer with 44 wt.% of long grafts showed a segregated morphology of nano-domains with sharp interfaces and a radius of gyration of 11.5 nm (from Guinier’s law). These cellulose acetate copolymers eventually led to strong films with potential applications in membrane separations.     

Application of cellulose acetate butyrate-based membrane for osmotic drug delivery

The release rate of drugs from an OROS^® is controlled by semipermeable membranes composed typically of cellulose acetate (CA) with various flux enhancers. Cellulose acetate butyrate (CAB) was identified as a viable alternative. The CAB membrane matched the CA membrane in robustness but had superior drying properties, offering particular advantages for thermolabile formulations. Studies were conducted to characterize CAB membrane properties with respect to performance of OROS^® systems. Four different membrane formulations with varying plasticizer type and concentration were investigated. The CAB based membranes exhibited superior drying characteristics and similar functionality to the CA:polyethylene glycol (PEG) membranes used as a control. A linear relationship was observed between the level of flux enhancer and release rate. The stability of the membrane was evaluated based on release profiles after system storage at various conditions. The CAB membranes appeared to have stability comparable to the standard CA membrane. A linear relationship between membrane weight and release rate as well as the time required to release 90% of a drug from the system [T₉₀] for a model formulation was observed. In conclusion, the newly identified alternative membrane composition allows for the use of thinner membranes, thereby reducing cost of goods, coating time and, most importantly, membrane drying time.     

Membrane selectivity for an aqueous system by dynamic osmometry

Commercial and fractionated samples of poly(ethylene glycol) and a sample of Dextran were used as standards to show the limitation of a cellulose acetate membrane for osmotic pressure determination of molecular weight in an aqueous system. The leakage of this membrane was much greater in the aqueous system than in organic solvents.     

Synthesis and properties of amphiphilic vinyl acetate triblock copolymers prepared by copper mediated living radical polymerisation

Polymerisation of vinyl acetate by conventional free radical polymerisation using a diazo initiator followed by copper mediated living radical polymerisation with a range of monomers was studied. This method led to the synthesis of triblock copolymers. We have thus successfully prepared several new ABA triblock copolymers where B is poly(vinyl acetate) and A is (dimethylamino)ethyl methacrylate (DMAEMA), (polyethylene glycol) methyl ether methacrylate (MeO(PEG)MA) or solketal methacrylate (SMA). The sequential conventional/living radical polymerisation approach provided an efficient route to synthesis of new block copolymers. The properties of these amphiphilic polymers have been subsequently investigated by ¹H NMR, fluorescence spectroscopy, tensiometry and dynamic light scattering to investigate their behaviour as potential surfactants.     

Copolymerization of methacrylic acid with methyl methacrylate on a polyethylene glycol matrix

Copolymerization of methacrylic acid with [¹⁴C]-methyl methacrylate was carried out in the presence of polyethylene glycol (PEG) as a matrix. Composition and structure of complexes were determined using NMR techniques and radiometric measurements. It was found that the complexes consist of copolymer and PEG. Dependence of the composition of the copolymer on the composition of the initial mixture of monomers was examined. The reactivity ratios were calculated and compared with those for copolymerization without matrix. It was found that the influence of polyethylene glycol results in changing reactivity ratios of comonomers and kinetics of the process.     

Cold NaOH/urea aqueous dissolved cellulose for benzylation: Synthesis and characterization

Cold NaOH/urea aqueous dissolved cellulose was studied for the synthesis of benzyl cellulose by etherification with benzyl chloride. By varying the molar ratios of benzyl chloride to OH groups in cellulose (1.5–4.0) and reaction temperatures (65–70 °C), benzyl cellulose with a degree of substitutions (DS) in the range of 0.29–0.54 was successfully prepared under such mild conditions. The incorporation of benzyl groups into cellulose was evidenced by multiple spectroscopies, including FT IR, ¹H NMR, ¹³C NMR, CP/MAS ¹³C NMR and XRD. In addition, the thermal stability and surface morphology of the benzyl cellulose was also investigated with regard to the degree of substitution. The results indicated that the benzyl cellulose product with a low DS (0.51) in the present study reached the same solubility in many organic solvents as compared to those prepared in heterogeneous media. After benzylation, the sample decomposed at a lower temperature with a wider temperature range, which indicated that the thermal stability of benzyl cellulose was lower than that of the native cellulose. In addition, benzylation resulted in a pronounced reduction in crystallinity as well as a fundamental alteration of morphology of the native cellulose.     

A Carbohydrate–Anion Recognition System in Aprotic Solvents

A carbohydrate–anion recognition system in nonpolar solvents is reported, in which complexes form at the B‐faces of β‐D ‐pyranosides with H1‐, H3‐, and H5‐cis patterns similar to carbohydrate–π interactions. The complexation effect was evaluated for a range of carbohydrate structures; it resulted in either 1:1 carbohydrate–anion complexes, or 1:2 complex formation depending on the protection pattern of the carbohydrate. The interaction was also evaluated with different anions and solvents. In both cases it resulted in significant binding differences. The results indicate that complexation originates from van der Waals interactions or weak CH ??? A^? hydrogen bonds between the binding partners and is related to electron‐withdrawing groups of the carbohydrates as well as increased hydrogen‐bond‐accepting capability of the anions.     

Dioxouranium (VI) complexes with cellulose acetate

Dioxouranium [UO₂(VI)] complexes with three degrees of substitution of cellulose acetate, prepared from viscose pulp (DS = 2.2, 2.45 and 2.86), have been synthesis and characterized. Degree of substitution (DS) is defined as the average number of CH groups substituted on each anhydrocellulose repeat unit. Probable structures of the cellulose acetate complexes were inferred from the elemental analysis data, conductance measurements, IR, electronic and ¹H NMR spectra. The results obtained show that the formula of UO₂(VI) complex with cellulose acetate of DS = 2.2 and 2.45 [(CA)₄.UO₂] is more probable than [(CA)₂.UO₂].2(CH₃COO), while the reverse is true for the case of a UO₂ complex with CA of DS = 2.86. For the former formula, cellulose acetate acts as a uni-negatively charged bidentate ligand and reacts with UO₂²⁺ through the ether-carbon-oxygen of the secondary acetylated hydroxyl group of the anhydroglucose unit and the oxygen atom of the residual secondary unacetylated hydroxyl group, forming a five-membered chelate ring. For the later formula, cellulose acetate of DS = 2.86 acts as a neutral bidentate chelating agent through the two ether oxygen atoms of the vicinal ester groups of secondary acetylated hydroxyl groups in anhydroglucose units also forming a five-membered chelate ring. The uranium atom in these complexes is 8-coordinate. The thermal behaviour of cellulose diacetate (DS = 2.2) and cellulose triacetate (DS = 2.86) and their complexes with uranyl acetate in nitrogen atmosphere has been also studied by differential thermal analysis from room temperature to 600 °C. The obtained DTA curves were analyzed using the Prout-Tompkins law. The method of least squares was applied to estimate the appropriate order of the reaction (n), and consequently the thermodynamic parameters. The results revealed that chelation of cellulose acetate with uranyl acetate led to increased thermal stability.     

Multidimensional chromatographic techniques for hydrophilic copolymers II. Analysis of poly(ethylene glycol)-poly(vinyl acetate) graft copolymers

A large variety of hydrophilic copolymers is applied in different fields of chemical industry including bio, pharma and pharmaceutical applications. For example, poly(ethylene glycol)-poly(vinyl alcohol) graft copolymers that are used as tablet coatings are responsible for the controlled release of the active compounds. These copolymers are produced by grafting of vinyl acetate onto polyethylene glycol (PEG) and subsequent hydrolysis of the poly(ethylene glycol)-poly(vinyl acetate) graft copolymers. The poly(ethylene glycol)-poly(vinyl acetate) copolymers are distributed with regard to molar mass and chemical composition. In addition, they frequently contain the homopolymers polyethylene glycol and polyvinyl acetate. The comprehensive analysis of such complex systems requires hyphenated analytical techniques, including two-dimensional liquid chromatography and combined LC and nuclear magnetic resonance spectroscopy. The development and application of these techniques are discussed in the present paper.