Phase Behavior of Poly(Oxyethylene)–Poly(Oxypropylene)–Poly(Oxyethylene) Block Copolymer in Water and Water–C12EO5 Systems

Abstract

The binary phase diagram of a triblock copolymer poly(oxyethylene) (PEO) poly(oxypropylene) (PPO) poly(oxyethylene) (PEO), (PEO)₃₇(PPO)₅₈(PEO)₃₇ or P105 in water and the ternary system of P105, water, and pentaoxyethylene dodecyl ether (C₁₂EO₅) has been studied to understand the miscibility of a small amphiphile, C₁₂EO₅ and a copolymer, as well as the mixing effect on the formed liquid crystalline structures. Phase diagrams, small angle x‐ray scattering (SAXS) and differential scanning calorimetry (DSC) were used to characterize these systems. The phase diagram of the binary system is presented together with the characteristic parameters for founded phases, namely, cubic, hexagonal, and lamellar phases. In the ternary system it was found that the small amphiphile and the block copolymer, despite having very different chain lengths are essentially miscible forming single phases. A large amount of C₁₂EO₅ can be solubilized in the P105 aggregates whereas P105 is most difficult to dissolve in the C₁₂EO₅ aggregates because of the difference in the molecular size. The copolymer is practically insoluble in the lamellar phase of C₁₂EO₅ due to the packing constraint. Hence, two lamellar phases coexist in a surfactant‐rich region, at W _s  = 0.66, where W _s is the weight fraction of the total amphiphile in the system. This indicates that the thickness of the lipophilic part of the C₁₂EO₅ lamellar phase is too small to allocate the large lipophilic chain of the P105 triblock copolymer.     

The Synthesis of Soluble Copolymer of Poly(p-Phenylene Vinylene)

Poly(p-phenylenevinylene)rePV)anditsderivahveshavearousedgreatinterest,'sinceBurroughes:discoveredthatPPVshowedexcellentelectrolulninescent(EL)propenies.However,PPVanditsderivativessynfllesizedbyconventionalpolylnerizationreachons3areusuallyinsolubleandidesible,whichshowsinferiormechanicalpropelles.AlthoughtheprecursorpolymerroutecancircmnventfileinsolubilityofPPV,thestrategyneedsamuhStCpreachonandlhghtemperaturewlticllaffordslowyieldandoillerdisadvantages.'So,theSynthesisofsolublePPVd…     

Synthesis and Characterization of Amphiphilic Block Copolymer Containing PVP and Poly(5-benzyloxytrimethylene carbonate)

Amphiphilic block copolymers have attracted great interest recently, especially for thebiomedical uses1, . The hydrophilic blocks improve the biocompatibility of copolymer, 2while the hydrophobic blocks enhance the mechanics of the material and providever…     

Aggregation Behavior of Poly(ethylene glycol)-block-poly (γ-benzyl L-glutamate)-graft-poly(ethylene glycol) Copolymer and its Blends with Poly(γ-benzyl L-glutamate) Homopolymer in Mixed Solvents

Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with mPEG. The self-association behaviors of PEG-b-PBLG-g-PEG and its blends with PBLG homopolymer in the mixtures of ethanol and dimethylformamide (DMF) were investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and viscometry. Effects of the introduction of PBLG homopolymer, the grafting ratio, and the DMF content on the self-association behaviors of PEG-b-PBLG-g-PEG copolymer in the mixtures of ethanol and DMF were mainly researched. It was revealed that PEG-b-PBLG-g-PEG copolymer could self-assemble to form polymeric micelles with a core-shell structure in various shapes from different preparation conditions. The critical micelle concentration (CMC) and the average particle diameter of the micelles formed by PEG-b-PBLG-g-PEG copolymer in the mixed solvents also changed with different preparation conditions.     

Enzymatic Synthesis and Characterization of Novel Amphiphilic Triblock Copolymer Poly（p-dioxanoneco-5-benzyloxytrimethylene carbonate）-block-poly（ethylene glycol）

In recent years, amphiphilic block copolymers consisting of hydrophilic and hydrophobic segments have attracted much attention, because of their unique phase behavior in aqueous media and potential applications as drug delivery systems1. Poly(ethylene gly…     

Synthesis and Thermal Behavior of Poly(2-hydroxyethoxybenzoate) and Its Copolyesters with ε-caprolactone

Poly(2-hydroxyethoxybenzoate), poly(ε-caprolactone), and random poly(2-hydroxyethoxybenzoate/e-caprolactone) copolymers were synthesized and characterized in terms of chemical structure and molecular mass. The thermal behavior was examined by DSC. All the samples appear as semicrystalline materials; the main effect of copolymerization was lowering in the amount of crystallinity and a decrease of melting temperature with respect to homopolymers. Flory's equation described well the T _m-composition data. Amorphous samples (in the 20–100%2-hydroxyethoxybenzoate unit concentration range) obtained by quenching showed amonotonic decrease of the glass transition temperature T _g as the content of caprolactone units is increased. The Wood's equation described the T _g-composition data well. This revised version was published online in July 2006 with corrections to the Cover Date.     

Swelling Behavior and Metal-Ion Uptake Capacity of pH-Responsive Hydrogels of Poly(N-acryloyl-N′-ethylpiperazine)

New hydrogels based on N-acryloyl-N′-ethylpiperazine (AcrNEP) and N,N-methylene bisacrylamide (MBA) were prepared by thermal initiated solution polymerization. The hydrogels swelled extensively in buffer solutions of low pH due to protonation of the amine functions of the monomers, while the swelling was less significant in buffer solutions of high pH. The increased swelling of the gel in low pH is due to the development and interaction of fixed charges within the gel network. As a result of the electrostatic repulsion between the charges the elastic constraint of the gel is modified which leads to pronounced swelling and hence to high water uptake. Water transport in the hydrogel both in buffer solutions of pH 2.6 and pH 8.4 was non-Fickian due to polymer relaxation (anomalous process). The gels demonstrated good uptake of divalent metal ions such as Ni²⁺, Co²⁺, and Zn²⁺, with high selectivity for Ni²⁺ ions due to the formation of a more stable ligand-metal complex. The metal uptake capacity increased with increase in pH of the solution, while an increase in the crosslinker amount of the hydrogel reduced its metal uptake capacity. In the presence of metal ions the swelling of the hydrogel reduced considerably due to the formation of additional physical crosslinks within the hydrogel network. The metal ion loaded hydrogels could be stripped and regenerated with 1 M sulfuric acid without any loss in swelling or metal uptake capacities.     

Synthesis and Characterization of Poly(isoprene-b-butyl methacrylate) Block Copolymer in the Presence of Rare Earth Catalyst

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Block Copolymer Networks Composed of Poly(ε-caprolactone) and Polyethylene with Triple Shape Memory Properties

In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated PCL and PE telechelics. First, α,ω-dihydroxylterminated PCL and PE telechelics were synthesized via the ring-opening polymerization of ε-caprolactone and the ring-opening metathesis polymerization of cyclooctene followed by hydrogenation of polycyclooctene. Both α,ω-ditriethoxylsilane-terminated PCL and PE telechelics were obtained via in situ reaction of α,ω-dihydroxyl-terminated PCL and PE telechelics with 3-isocyanatopropyltriethoxysilane. The formation of networks was evidenced by the solubility and rheological tests. It was found that the block copolymer networks were microphase-separated. The PCL and PE blocks still preserved the crystallinity. Owing to the formation of crosslinked networks, the materials displayed shape memory properties. More importantly, the combination of PCL with PE resulted that the block copolymer networks had the triple shape memory properties, which can be triggered with the melting and crystallization of PCL and PE blocks. The results reported in this work demonstrated that triple shape memory polymers could be prepared via the formation of block copolymer networks.     

Factors of Influencing the Grafting Ratio of Poly(γ-benzyl-L-glutamate)-graft-Poly (ethylene glycol) Copolymer

Poly(γ-benzyl-L-glutamate)-graft-poly(ethylene glycol) (PBLG-graft-PEG) copolymer was synthesized by the ester exchange reaction of PBLG with PEG. Nuclear magnetic resonance (NMR) spectroscopy and scanning electron microscopy (SEM) were used to characterize the structure of PBLG-graft-PEG copolymer. The effects of reaction temperature, reaction time, and the chain length of PEG on the grafting ratio of PBLG-graft-PEG copolymer were investigated.     

“Grafting From” -Living Cationic Polymerization of Poly(isobutylene) from Silica-Nanoparticle Surfaces

Summary: This publication discusses the development of new methods for producing organic-inorganic core-shell-nanoparticles (NP's) via a combination of “grafting-from” techniques and living cationic polymerization reactions. Based on the surface initiated, quasiliving cationic polymerization of isobutylene, polymeric shells of polyisobutylene (PIB) were attached onto nanoparticles (silica NP's of different sizes, r = 12–40 nm) with a high degree of precision. “Grafting-from” polymerization provides an ideal method to control the number of polymer chains per particle by means of the degree of initial derivatization and the length of the polymeric chains. The resulting nanocomposite materials were analyzed using DLS, TEM, GPC, TGA, DSC.     

Raman Spectroscopic Study of the Conformation and Melting of Poly(dG) · Poly(dC) and Poly(dG-dC) · Poly(dG-dC) in Aqueous Solution

Raman spectroscopic measurements on aqueous solutions of poly(dG) · poly(dC)indicate that the conformation of the polynucleotides in this double helicalcomplex are distributed between the A and B types at room temperature, the Aform being predominant at –15°C and decreasing progressively upon raising thetemperature to 65°C. A reversible pretransition has been found in this complexnear 70°C. Modifications in the spectra at this temperature indicate no majorconformational changes, but rather suggest altered base pairing and hydration ofthe carbonyl groups, accompanied by a slight distortion of the double helix,resulting in a slightly reduced stacking of the cytosine bases. Measurements inself-pressurized solutions of the complex at high temperature show that it meltsat 103°C in 0.1M NaCl solution (107°C in 0.5M NaCl). These values are somewhatlower than those we have determined in the same manner for the complexpoly(dG-dC) · poly(dG-dC): 117°C in 0.1M MgCl₂ and 113°C or higher in 0.1MNaCl solution.     

An Observation on the Microphase Separation of Poly(methyl methacrylate)-block-Polystyrene Copolymer

The well-ordered structures of block copolymer formed by self-assemble have attracted much attention as potentially interesting optical materials, especially as photonic crystals1,2. In order to achieve desirable photonic crystal properties, the morphologies of block copolymers should be controlled, including obtaining the correct size of domains for the optical frequencies of interest and attainment of long-range domain order and appropriate orientation. We know that the morphology of one blo…     

Study on Self-assembly of Poly(ethylene glycol)- block-poly(γ-benzyl L -glutamate)-graft-poly(ethylene glycol) Copolymer and Poly(γ-benzyl L -glutamate)- block-poly(ethylene glycol) Copolymer in Ethanol

Poly(ethylene glycol)-block-poly(γ-benzyl L-glutamate)-graft-poly(ethylene glycol) (PEG-b-PBLG-g-PEG) copolymer was synthesized by the ester exchange reaction of poly(γ-benzyl L-glutamate)-block-poly(ethylene glycol) (PBLG-block-PEG) copolymer with PEG chain, and PBLG-block-PEG copolymer was prepared by a standard N-carboxyl-γ-benzyl-L-glutamate anhydride (NCA) method. Nuclear magnetic resonance (NMR) spectroscopy was used to confirm the components of PBLG-block-PEG and PEG-b-PBLG-g-PEG. The self-association behaviors of PBLG-block-PEG and PEG-b-PBLG-g-PEG in ethanol were investigated by transmission electron microscopy (TEM), dynamic laser scattering (DLS), and viscometry. The experimental results revealed that the different molecular structures could exert marked effects on the self-assembly behaviors of PBLG-block-PEG and PEG-b-PBLG-g-PEG in ethanol. PBLG-block-PEG and PEG-b-PBLG-g-PEG could self-assemble to form polymeric micelles with a core-shell structure in the shapes of plump spherical and regular rice-like, respectively. Effects of the introduction of PBLG homopolymer on the average particle diameter of the micelles of PBLG-block-PEG and PEG-b-PBLG-g-PEG and influence of testing temperature on the critical micelle concentration of different copolymers were studied.     

Conducting Block Copolymer Nanowires Containing Regioregular Poly(3‐Hexylthiophene) and Polystyrene

Grignard Metathesis polymerization (GRIM) for the synthesis of regioregular poly(3‐alkylthiophenes) proceeds via a “living” chain growth mechanism. Due to the “living” nature of this polymerization regioregular poly(3‐alkylthiophenes) with predetermined molecular weight, narrow molecular weight distributions and desired chain end functionality are now readily available. Allyl terminated poly(3‐hexylthiophene) was successfully used as a precursor for the synthesis of di‐block copolymers containing polystyrene. The addition of “living” poly(styryl)lithium to the allyl terminated regioregular poly(3‐hexylthiophene) generated the di‐block copolymer. Poly(3‐hexylthiophene)‐b‐polystyrene was also synthesized by atom transfer radical polymerization. Integration of poly(3‐hexylthiophene) in di‐block copolymers with polystyrene leads to the formation of nanowire morphology and self‐ordered conducting nanostructured materials.     

Electrochemical Behavior and Redox Switch Properties of [Zn(dmit)_2]~(2-)

The redox behavior of [Zn(dmit)2]2- and its electrodeposited film were investigated by cyclic voltammetry, and the Ⅰ-Ⅴ properties of the electrodeposited film were measured. The results show that [Zn(dmit)2]2- possesses good redox switch properties which exhibit good repeatability. It could be considered as a new material for molecular switch and memory.     

Structural Characterization of Poly(α-Fluoroacrylonitrile) and Poly(Ethyl α-Fluoroacrylate)

Abstract

Monomers α-fluoroacrylonitrile (FAN) and ethyl α-fluoroacrylate (EFA) and homopolymers poly(α-fluoroacrylonitrile) (PFAN) and poly-(ethyl α-fluoroacrylate) (PEFA) have been synthesized and spectroscopi-cally characterized in detail for the first time. The ¹³C- and ¹⁹F-NMR spectroscopic results are reported, and the results are correlated to the tacticity and microstructure of both homopolymers. The major portion of the polymers is atactic. TGA analysis of PFAN indicates that the polymer is stable to about 200°C with subsequent loss of HF. PEFA is stable to 300 °C. Molecular weights determined by intrinsic viscosity (M_v ) are found to be about 130,000 for PFAN, and GPC analysis of PEFA indicates a molecular weight (M_n ) of about 36,000. Dielectric permittivities (ε) for PFAN and PEFA were determined to be 8.9 and 4.0, respectively, at 50 Hz.     

Erratum to “Nanocrystallization-locked Network of Poly(styrene-b-isobutylene-b-styrene)-g-Polytetrahydrofuran Block Graft Copolymer”

Chinese Journal of Polymer Science -     

Phase Behavior and Morphology of Poly(Methyl Methacrylate)/Poly(α‐Methyl Styrene‐co‐Acrylonitrile) Blends Under Quiescent and Shear Flow

The kinetics of spinodal decomposition (SD) for the binary blend poly(methyl methacrylate), PMMA, and Poly(α‐methylstyrene‐co‐acrylonitrile), PαMSAN, with 31 wt% AN content (LCST‐type phase diagram) has been thoroughly studied using a time‐resolved light scattering technique. The early stage SD was dominated by a diffusion process and can be well described within the framework of the linearized Cahn‐Hilliard theory. The spinodal temperature could be evaluated from the analysis of the early stage SD based on the Cahn theory. In addition, viscoelastic properties of this system have been systematically investigated at temperatures below and above the LCST phase diagram. The linear viscoelastic properties of the blends were found to be greatly changed by phase separation in the two‐phase regime. This change in the linear viscoelastic properties attributed to an additional contribution of concentration fluctuations to the material functions at the phase separation temperatures. The phase diagram of the blends was also estimated rheologically through the dynamic temperature ramps of G′, G″ and η*. Furthermore, the phase behavior and morphology of this system has been studied under different shear rates using simple shear apparatus and transmission electron microscopy (TEM), respectively.     

Living Cationic Sequential Block Copolymerization of Isobutylene with 4‐tert‐Butoxystyrene: Synthesis and Characterization of Poly(p‐hydroxystyrene‐b‐isobutylene‐b‐p‐hydroxystyrene) Triblock Copolymers

The living polymerization of p‐tert‐butoxystyrene (tBuOS) was studied in methylcyclohexane (MeChx)/methylchloride (MeCl) 60/40 v/v solvent mixture at –80°C. The model initiator 1,1,‐ditolylethylene (DTE) capped 2‐chloro‐2,4,4‐trimethylpentane (TMPCl) was formed in situ in conjunction with TiCl₄. Lowering the Lewis acidity by the addition of Ti(OIp)₄ was necessary to induce a rapid and controlled polymerization of tBuOS. Well‐defined polymers with controlled molecular weights, however, were only obtained at a narrow [Ti(OIp)₄]/[TiCl₄]=0.83–0.86 ratio. Above this ratio, the polymerization of tBuOS was slow and became absent at [Ti(OIp)₄]/[TiCl₄]≥1.18. At ratios lower than 0.83, the polymerization was too rapid and the initiator efficiency was lower than 100%. The living polymerization of tBuOS was also studied with SnBr₄ as Lewis acid. After capping TMPCl with DTE, Ti(OIp)₄ was added to reach [Ti(OIp)₄]/[TiCl₄]=1.2, followed by the addition of tBuOS and SnBr₄. SnBr₄ induced a well‐controlled living polymerization approximately first order in [SnBr₄], and the polymers exhibited close to theoretical M _ns and low polydispersity indices (PDI<1.2). The success of the method was also demonstrated by the clean synthesis of poly(isobutylene‐b‐p‐tert‐butoxystyrene) PIB‐b‐PtBuOS diblock copolymers. PtBuOS‐b‐PIB‐b‐PtBuOS triblock copolymer thermoplastic elastomers were prepared by employing 5‐tert‐butyl‐1,3‐bis(1‐methoxy‐1‐methylethyl)benzene (DCE) as a difunctional initiator for the living polymerization of IB followed by capping with DTE and substitution of TiCl₄ with SnBr₄ for the polymerization of tBuOS. Deprotection of the triblock copolymer in the presence of catalytic amount of HCl yielded poly(p‐hydroxystyrene‐b‐isobutylene‐b‐p‐hydroxystyrene) (PHOS‐b‐PIB‐b‐PHOS). PHOS‐b‐PIB‐b‐PHOS with 39.3 wt% p‐hydroxystyrene content exhibited typical characteristic of a thermoplastic elastomers (TPEs) with tensile strength of 18 MPa and ultimate elongation of 300%.