Drying dissipative structures of aqueous solution of poly (ethylene glycol) on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying a series of poly (ethylene glycol) (PEG) having molecular weights ranging from 1,000 to 2×10⁶ in aqueous solution have been studied on a cover glass. The broad ring patterns of the hill accumulated with the polymers are formed irrespective of the molecular weights of PEG molecules. The single round hills are formed also in the center in the macroscopic scale, when the molecular weight is large. The characteristic convection flow of the polymers and the interactions among the polymers and substrate are important for the macroscopic pattern formation. Cross-like fractal patterns are observed, especially for the diluted solutions in the microscopic scale. These patterns are determined mainly by the electrostatic and polar interactions between the polymers and/or between the polymer and the substrate in the course of solidification. Interestingly, these microscopic patterns are reflected based on the shape and size of the PEG polymers.     

Dissipative structures formed in the course of drying an aqueous solution of poly(allylamine hydrochloride) on a cover glass

Macroscopic and microscopic dissipative structural patterns formed in the course of drying a deionized aqueous solution of cationic polyelectrolyte, poly(allylamine hydrochloride) on a cover glass have been observed. Drying times range from 40 min at 45 °C to 450 min at 5 °C, and are insensitive to the polymer concentration. Pattern area shrinks toward the center at the low polymer concentrations, and increases as the concentration increases. A macroscopic broad ring pattern, where the polymer accumulates densely, forms in many cases. Beautiful fractal patterns are observed at the microscopic scale. The fractal dimension increases from 1.2 to 1.6 as polymer concentration increases from 10^-6 monoM to 10^-2 monoM. The relative rates between the water flow at the drying front and the convection flow of water accompanying the movement of polymer are important for the macroscopic and microscopic pattern formation.     

Drying dissipative structures of the thermosensitive gels of poly(N-isopropyl acrylamide) on a cover glass

Drying dissipative structural patterns of the thermosensitive gels of poly(N-isopropyl acrylamide) were studied on a cover glass. As the temperature of suspension and room rose from 25 to 50 °C, the small size of drying pattern area extended to the beautiful flickering spoke-like ones transitionally at the critical temperature ca. 35 °C. The principal patterns at 25 °C were the single or multiple broad rings of the hill accumulated with the gels. At 50 °C, on the other hand, the flickering spoke-like patterns were observed at the inner area of the broad ring especially at the gel concentrations higher than 1 × 10⁻³ g/ml. These observations support that the extended gels at low temperatures apt to associate weakly to each other, whereas the gels at high temperatures shrink and move rather freely with the convectional flow of water, though the very weak intergel attractions still remain. In the presence of sodium chloride at high temperatures, the cooperative patterns formed between the gel spheres and the salt. The gravitational and Marangoni convectional flow of the gels and the very weak interactions between the gels and substrate (cover glass) are important for the flickering spoke-like pattern formation.     

Sedimentation and drying dissipative patterns of colloidal crystals of poly(methyl methacrylate) spheres in a glass dish

In a series of our studies on the dissipative structure formation, this work focused on the sedimentation and drying patterns of colloidal crystals of poly(methyl methacrylate) colloidal spheres with different sizes (100, 200, 300, and 1,000 nm in diameter) in a glass dish. During the course of dryness, the brilliant iridescent colors changed. Drying frontier grew from the central area of the cell toward the outside edge. Macroscopic and microscopic drying patterns of the resulting film from dried colloidal suspensions showed outer and inner broad rings. Size of the outer rings increased with increasing sphere concentration but did not altered sphere size, while these factors affected the inner ring size. These observations do not support the pinning effect proposed by Deegan et al.     

Convectional,sedimentation and drying dissipative patterns of colloidal crystals of poly(methyl methacrylate) spheres on a watch glass

Direct observation of the convectional dissipative patterns at room temperature was successful on a cover glass during the course of dryness of colloidal crystals of poly(methyl methacrylate) colloidal spheres. Formation processes of the convectional patterns of spoke-like lines were observed as a function of sphere size and also sphere concentration. During dryness of the suspensions, the brilliant iridescent colors changed beautifully. Macroscopic and microscopic drying patterns of the dried film were observed. Multiple broad ring-like patterns were observed especially at low sphere concentrations. The water evaporation accompanied with the convectional flow of water and the colloidal spheres played an important role for the dissipative structure formation.     

Convectional,sedimentation, and drying dissipative patterns of colloidal crystals of poly (methyl methacrylate) spheres on a cover glass

Direct observation of the convectional dissipative patterns was successful during the course of dryness of colloidal crystals of poly (methyl methacrylate) spheres on a cover glass. Formation processes of the convectional patterns of spoke-like lines were observed as a function of sphere size and also sphere concentration. During dryness of the suspensions, the brilliant iridescent colors changed beautifully. Macro- and microscopic drying patterns and thickness profiles of the dried film were observed. Sharp broad rings were observed especially at low sphere concentrations. The water evaporation accompanied with the convectional flow of water and the colloidal spheres played an important role for these dissipative structure formation.     

Drying dissipative structures of Chinese black ink on a cover glass and in a dish

Macroscopic and microscopic dissipative structural patterns are formed in the course of drying a suspension of Chinese black ink on a cover glass and in a dish. The time for the drying and the pattern area increased as the particle concentration increased. The broad ring patterns of the hills accumulated with the particles formed around the outside edges on a macroscopic scale. The height and the width of the broad ring increased as the particle concentration increased. The spokelike patterns of the rims accumulated with particles were also formed on a macroscopic scale. Microscopic patterns of colloidal accumulation were observed over the whole region of the pattern area. Various types of convection cells were observed on a cover glass and in a dish at 25–80 °C. A time-resolved observation of the drying process was also made. The convections of water and the colloidal particles at different rates under gravity and the translational and rotational Brownian movement of the particles were important for the macroscopic pattern formation. Microscopic patterns were determined by the translational Brownian diffusion of the particles and the electrostatic and the hydrophobic interactions between the particles and/or between the particles and the cell wall in the course of the solidification of the particles.     

New architectures of poly(ethylene glycol) and poly(methylthiirane) in block copolymers

Two synthetic ways were experimented to prepare new architectures of block copolymers made of poly(ethylene glycol) (PEG) and poly(methylthiirane). The coupling of both blocks conveniently end-capped as well as anionic polymerization of methylthiirane initiated by PEG-thiols gave readily the copolymers. Their characterization by ¹H NMR, SEC and IR confirmed the expected structures.     

Crystallization of photo-chain extended poly(ethylene glycol)

Coumarin-functionalized poly(ethylene glycol) (PEG) monols and diols were isothermally crystallized at temperatures between 20 and 35 °C before and after exposure to approximately 110 J cm⁻² of ultra-violet A (λ > 300 nm, UVA) irradiation. Irradiation dimerized the coumarin groups and chain-extended the coumarin-functionalized PEG oligomers. The higher molecular weights reduced the crystal growth rate by as much as 50% compared to the non-irradiated coumarin-functionalized PEG oligomers under ambient crystallization conditions. Hoffman’s kinetic nucleation theory was utilized to evaluate the types of nucleation that occurred for the coumarin-functionalized PEG diols (COU-PEG-COU). Crystallization regimes II and III were observed for the coumarin-modified PEG oligomers before and after exposure to UVA light.     

Effect of temperature on the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions

In this work the intrinsic viscosity of poly(ethylene glycol)/poly(vinyl pyrrolidone) blends in aqueous solutions were measured at 283.1–313.1 K. The expansion factor of polymer chain was calculated by use of the intrinsic viscosities data. The thermodynamic parameters of polymer solution (the entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer–solvent interaction parameter and second osmotic virial coefficient) were evaluated by temperature dependence of polymer chain expansion factor. The obtained thermodynamic parameters indicate that quality of water was decreased for solutions of poly(ethylene oxide), poly(vinyl pyrrolidone) and poly(ethylene oxide)/poly(vinyl pyrrolidone) blends by increasing temperature. Compatibility of poly(ethylene oxide)/poly(vinyl pyrrolidone) blends were explained in terms of difference between experimental and ideal intrinsic viscosity and solvent–polymer interaction parameter. The results indicate that the poly(ethylene glycol)/poly(vinyl pyrrolidone) blends were incompatible.     

Determination of poly(ethylene glycol)s by both normal-phase and reversed-phase modes of high-performance liquid chromatography

A normal-phase HPLC system using an amino column has been developed to characterise oligomers of poly(ethylene glycol)s (PEGs) of average M_r 400 to 2000 with derivatisation by dinitrobenzoate. Normal-phase HPLC with gradient elution using ternary solvents of hexane, dichloromethane and methanol has produced a baseline resolution for oligomers of PEG 400, 600 and 1000, while PEG 1000 and 2000 were analysed by using binary solvents of acetonitrile and water. Mixtures of PEGs have been determined by these HPLC systems. PEG 400 in a textile finish has also been determined with satisfactory recovery. It has been found that the hydroxyl group of solvents in normal-phase HPLC plays an important role in resolution and retention of PEG oligomers. Derivatisation efficiency for PEGs by dinitrobenzoyl chloride and quantitative determination of derivatised PEGs by HPLC have been studied. A reversed-phase (RP) mode of HPLC was examined for determination of PEG 400 oligomers. The normal-phase system provided greater resolution for oligomers of PEGs.     

An analysis of the complexation between poly(aspartic acid) and poly(ethylene glycol)

The compatibility between poly(aspartic acid) and poly(ethylene glycol) for the formation of an interpolymer complex (IPC) was investigated by dynamic rheology and evaluation of zeta potential values. The homogeneity of the realized IPC was observed by near infrared chemical imagistic (NIR-CI) technique. The data were sustained and underlined by the assessment of the compatibility between the polymeric compounds.     

Synthesis and properties of polymer brushes composed of poly(diphenylacetylene) main chain and poly(ethylene glycol) side chains

Novel cylindrical polymer brushes consisting of poly(diphenylacetylene) main chain and poly(poly(ethylene glycol) methyl ether monomethacrylate) (PPEGMA) side chains were synthesized by the diphenylacetylene macromonomer or side chain initiated atom transfer radical polymerization (ATRP) of poly(ethylene glycol) methyl ether monomethacrylate (PEGMA) from an bromo isobutyryl-bearing poly(diphenylacetylene) (poly(BrDPA)) method. The diphenylacetylene macromonomer, namely, DPA-PPEGMA, were prepared by the ATRP of PEGMA from bromo isobutyryl-bearing diphenylacetylene. DPA-PPEGMA was polymerized successfully with WCl₆-Ph₄Sn catalyst to give high molecular weight polymer brushes poly(DPA-PPEGMA). Meanwhile, polymer brushes (PDPA-g-PPEGMA) were obtained by ATRP of PEGMA from poly(BrDPA). The molecular weight of the side chains of PPEGMA could be controlled simply by modulating the ATRP time. The macromonomer and polymer brushes are soluble in nonpolar solvents such as toluene and chloroform. The polymers of poly(BrDPA) and poly(DPA-PPEGMA) absorb in the longer wavelength region, with two peaks at around 370 and 414 nm. The polymers are thermally stable and exhibit double crystallization and melting peaks during the cooling and heating scans.     

Preparation, characterization and biocompatibility of poly(ethylene glycol)-poly(n-butyl cyanoacrylate) nanocapsules with oil core via miniemulsion polymerization

A new type of nanocapsules with an oil core, coated by poly(ethylene glycol) (PEG) was designed. The loading efficiency and the biocompatibility of the polymeric nanocapsules were evaluated when it was used as a carrier for hydrophobic agent paclitaxel. The nanocapsules were synthesized through miniemulsion polymerization of butylcyanoacrylate (BCA) with PEG as initiator. The particle size and zeta potential of nanocapsules were influenced by the PEG content in the polymerization system. Fourier transform infrared (FTIR) spectra and ¹H NMR demonstrated the chemical coupling between PEG and poly(butylcyanoacrylate) (PBCA). Thermal characteristics of the copolymer were investigated by differential scanning calorimetry (DSC). The encapsulation efficiency increased concurrently with the increase of the PEG content in the system. The hemolytic assay and the cytotoxicity measurement showed that the PEG coating could significantly reduce the hemolytic potential and cytotoxicity of the nanocapsules. The results showed that the PEG-PBCA nanocapsules could be an effective carrier for hydrophobic agents.     

Thermal,morphological, mechanical and aging properties of polylactide blends with poly(ether urethane) based on chain-extension reaction of poly(ethylene glycol) using diisocyanate

Poly(ether urethane)s(PEU), including PEUI15 and PEUH15, were prepared through chain-extension reaction of poly(ethylene glycol)(PEG-1500) using diisocyanate as a chain extender, including isophorone diisocyanate(IPDI) and hexamethylene diisocyanate(HDI). These PEUs were used to toughen polylactide(PLA) by physical and reactive blending.Thermal, morphological, mechanical and aging properties of the blends were investigated in detail. These PEUs were partially compatible with PLA. The elongation at break of the reactive blends in the presence of triphenyl phosphate(TPP)for PLA with PEUH15 or PEUI15 was much higher than that of the physical blends. The aging test was carried out at-20 °C for 50 h in order to accelerate the crystallization of PEUs. The PEUs in the PLA/PEU blends produced crystallization and formed new phase separation with PLA, resulting in the declined toughness of blends. Fortunately, under the aging condition,although PEUH15 in blends could also form crystallization, the reactive blend of PLA/PEUH15/TPP(80/20/2) had higher toughness than the other blends. The elongation at break of PLA/PEUH15/TPP(80/20/2) dropped to 287% for the aging blend from 350% for the original blend. The tensile strength and modulus of PLA/PEUH15/TPP blend did not change obviously because of the crystallization of PEUH15.     

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide),PEG-b-(PNIPAM)_2,were successfully synthesized through atom transfer radical polymerization(ATRP).A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly(ethylene glycol) monomethyl ether(PEG).The copolymers were obtained via the ATRP of N-isopropylacrylamide(NIPAM) at 30℃with CuCl/Me_6TREN as a catalyst system and DMF/H_2O(v/v = 3:1) mixture as solvent.The resulting copo...     

Polycaprolactone–poly(ethylene glycol) block copolymer,I: synthesis and degradability in vitro

A new type of biodegradable polymer material, poly(caprolactone)–poly(ethylene glycol) block copolymer (PCL-b-PEG), was synthesized by means of direct copolycondensation of ε-caprolactone with poly(ethylene glycol) in the presence of a Ti(OBu)₄ catalyst. The degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL-b-PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.     

Methoxy poly(ethylene glycol)-b-poly(valerolactone) diblock polymeric micelles for enhanced encapsulation and protection of camptothecin

Amphiphilic block copolymers, methoxy poly(ethylene glycol)-b-poly(valerolactone) (mPEG-b-PVL), were synthesized via ring opening polymerization of δ-valerolactone in the presence of methoxy poly(ethylene glycol) (mPEG). The copolymers form micelle-like nanoparticles by their amphiphilic characteristics and their structures were examined by Nuclear Magnetic Resonance (NMR). The sizes of nanoparticles ranged from 60 to 120 nm as measured by dynamic light scattering detection, and were larger with higher molecular weight of the copolymers. The Critical Micelle Concentration (CMC) of these nanoparticles in water decreased with increasing molecular weight of hydrophobic segment. Stability analysis showed that the micellar solutions maintain their sizes at 37 °C for six weeks without aggregation or dissociation. The lyophilization method was better than the evaporation method when camptothecin (CPT) was incorporated to the micelles. The former method yielded higher CPT loading efficiency and lower aggregation. The loading efficiency of CPT could be more than 96% and a steady release rate of CPT was kept for twenty six days. Moreover, the mPEG-b-PVL polymeric micelles offered good protection of CPT lactone form at 37 °C for sixteen days. The copolymers showed no cytotoxicity towards L929 mouse muscular cells when incubated for one day. Taken together, the mPEG-b-PVL copolymer has potential to be used for the delivery of CPT or other similar drugs.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Determination of poly(ethylene glycol) 300 in long chain free fatty acid mixtures by reversed-phase high-performance liquid chromatography

A rapid sensitive method has been developed for the detection and quantitation of poly(ethylene glycol) 300 (PEG 300) in long-chain free fatty acid mixtures that requires minimal sample preparation. The PEG 300 was separated from the free fatty acids by RP-HPLC using a water–tetrahydrofuran gradient. PEG and the free fatty acids were detected using evaporative light scattering detection. The minimum detectable level of PEG in a free fatty acid mixture was 0.0125%.