Thermal behavior and specific interaction in high glass transition temperature PMMA copolymer

A series of high glass transition temperature copolymers based on poly(methyl methacrylate) (PMMA) were prepared by free radical copolymerization of methacrylamide and methyl methacrylate monomers in dioxane solvent. The thermal properties and hydrogen-bonding interactions of these poly(methacrylamide-co-methyl methacrylate) (PMAAM-co-PMMA) copolymers with various compositions were investigated by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, and solid-state nuclear magnetic resonance (NMR) spectroscopy. A large positive deviation in the behavior of T_g, based on the Kwei equation from DSC analyses, indicates that strong hydrogen bonding exists between these two monomer segments. The FTIR and solid-state NMR spectroscopic analyses give positive evidence for the hydrogen-bonding interaction between the carbonyl group of PMMA and the amide group of PMAAM (e.g. by displaying significant changes in chemical shifts). Furthermore, the proton spin-lattice relaxation time in the rotating frame (T_1ρ(H)) has one single value over the entire range of compositions of copolymers, and gives a value shorter than the average predicted. The proton relaxation behavior indicates the rigid nature of the copolymer.     

Compatibilising action of random and triblock copolymers of poly(styrene-butadiene) in polystyrene/polybutadiene blends: A study by electron microscopy, solid state NMR spectroscopy and mechanical measurements

Scanning electron microscopy, solid-state proton NMR spectroscopy and static mechanical analysis have been performed in order to evaluate the compatibilising action of random copolymers of polystyrene and polybutadiene and triblock copolymers of poly(styrene-butadiene-styrene) in incompatible polystyrene/polybutadiene (PS/PB) blends. Scanning electron microscopic examination of the cryofractured and etched surfaces showed high degree of compatibilising action of the triblock copolymers as evidenced by the very sharp decrease of the domain size of the dispersed phase followed by an increase at higher concentrations. This is a clear indication of interfacial saturation. These results were in agreement with the theoretical predictions of Noolandi and Hong. The random copolymer was not effective in compatibilising the system. Solid-state proton NMR experiments were performed on the uncompatibilised and compatibilised blends. The proton spin-lattice relaxation times in the laboratory frame, T₁(H), and in the rotating frame, T_1ρ(H), and spin-spin relaxation times, T₂(H), were carefully measured for the systems. Significant changes were observed for the systems compatibilised with triblock copolymers due to the preferential localisation of the copolymers at the PS/PB interface. However, the random copolymer did not have any compositional drift and is not an effective interface modifier in agreement with microscopy study. The static mechanical properties of the blends have also been analysed. The addition of triblock copolymers increased the mechanical properties of the blends. Finally, attempts have been made to correlate the NMR results with the microstructure and mechanical properties of the blends.     

Thermal and spectroscopic properties of zinc perchlorate/poly(vinylpyrrolidone) blends and a comparison with related hydrogen bonding systems

We have investigated the thermal and spectroscopic properties of blends of poly(vinylpyrrolidone) (PVP) with zinc perchlorate. Analyses by differential scanning calorimetry indicates that blending with zinc perchlorate increases the values of T_g of PVP. We calculated the interaction strength of the zinc salt/PVP blends based on an extended configuration entropy model. The presence of ion-dipole interactions between PVP and the zinc salt was confirmed based on Fourier transform infrared (FTIR) and solid-state NMR spectroscopies, which suggest that the zinc cations coordinate with the carbonyl groups of PVP. The single value of measured by solid-state NMR spectroscopy observed for all the zinc salt/PVP blends is smaller than that of pure PVP, which is a finding that indicates that the domain size of this blend system decreases upon increasing the zinc salt content. Based on FTIR and solid-state NMR spectroscopic analyses, we conclude that the ion-dipole interactions in the zinc salt/PVP blend are stronger than the hydrogen bonds in systems such as the poly(vinylphenol) (PVPh)/PVP blend and the PVPh-co-PVP copolymer.     

The environment of lithium ions and conductivity of comb-like polymer electrolyte with a chelating functional group

The behavior of lithium ions in a comb-like polymer electrolyte with a chelating functional group have been characterized by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy, ac impedance and ⁷Li solid-state NMR measurements. The comb-like copolymer is synthesized by poly(ethylene glycol-methyl ether methacrylate) (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino) -2-hydroxy-propyl ester) (GMA-IDA). FTIR and ⁷Li solid-state NMR spectra demonstrate the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. Moreover, ⁷Li solid-state NMR shows that the lithium ions are preferentially coordinated to the GMA-IDA segment. The T_g increases for the copolymers doped with LiClO₄. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chains. The dependence of the maximum conductivity on the composition of the copolymers and the doping lithium ion concentration was determined. The GMA-IDA unit in the copolymer improves the dissociation of the lithium salt, the mechanical strength and the conductivity.     

Significant thermal property and hydrogen bonding strength increase in poly(vinylphenol-co-vinylpyrrolidone) copolymer

A series of poly(vinylphenol-co-vinylpyrrolidone) (PVPh-co-PVP) copolymers were prepared by free radical copolymerization of acetoxystyrene with vinylpyrrolidone (PAS-co-PVP), followed by selective removal of the acetyl protective group. These copolymers were investigated by solid state nuclear magnetic resonance (NMR) and thermal gravimetric analyzer (TGA) to compare with previous results on differential scanning calorimetry (DSC) and Fourier-Transform infrared spectroscopy (FTIR) analyses. The spin-lattice relaxation time in the rotating frame (T_1ρ(H)) of the PVPh-co-PVP is greater than the corresponding PVPh/PVP blend, indicating that the polymer mobility is more restricted and high rigid character of the former. At the same time, the thermal decomposition temperature of homopolymer, copolymer and polymer blend is the order of PVPh-co-PVP copolymer>PVPh/PVP blend>pure PVP homopolymer>PAS-co-PVP copolymer and this order is consistent with previous studies on DSC, FTIR and NMR analyses. In order to understand the mechanism of significant glass transition temperature increase of the PVPh-co-PVP copolymer, the degree of hydrolysis was controlled by varying time of reaction of the PAS-co-PVP copolymer.     

Preparation of polymer brushes via growth of single crystals of poly(ethylene glycol)-block-polystyrene diblock copolymers synthesized by ATRP and studying the crystal lateral size and brush tethering density

Well-defined block copolymers of poly(ethylene glycol)-block-polystyrene (PEG-b-PS) were synthesized by atom transfer radical polymerization with predetermined molecular weights and narrow molecular weight distributions (1.06–1.08). The single crystals of PEG-b-PS copolymers were grown in chlorobenzene/octane mixed theta solvent using self-seeding technique. The effect of self-seeding temperature (T _s) on single crystal lateral size was evaluated. The atomic force microscopy (AFM) height images were indicative of increasing the single crystal lateral sizes, which were of several microns, via elevating T _s. The non-ideal structures were increasing by moving away from the optimized T _s (41.5 °C). Here, we studied the transition point between non-interaction and interaction regimes in a mixed theta solvent for PS as well. The impact of the PS block hindrance and the influence of crystallization temperature on thickness, tethering density and reduced tethering density of PS brushes were also investigated. Although these factors did not have the same effect on thickness and tethering density, the trend of their influence on reduced tethering density was the same. The results were recognized by AFM, transmission electron microscopy and small angle X-ray scattering.     

Morphologies of an Amphiphilic Diblock Copolymer of Poly (Ethylene Oxide)-b-Polystyrene and Its Blends with Poly (2,6-Dimethyl-1,4-Oxide)

Systems containing block copolymers are of great interest due to the ability of copolymers to self-assemble into a variety of structured, ordered, or partially ordered morphologies. A fascinating morphology of two-dimensional arrays of hexagonal-like holes was observed for the first time in the diblock copolymer of poly (ethylene oxide)-b-polystyrene (PEO-b-PS) by transmission electron microscopy (TEM). The blends of PEO-b-PS with poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) were obtained by solution blending, and the morphologies of PEO nano-dispersed particles in PPO/PS matrix were observed by atomic force microscopy (AFM) and TEM. Using the film forming technique on water/air interface, the core-shell morphology with PEO as shells was obtained in PEO-b-PS/PPO blends. Thus, three different morphologies were obtained by controlling preparation conditions. Especially, PEO-b-PS self-organized into the hexagonal-like holes patterns was first found to our knowledge.     

Synthesis of poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene triblock copolymers by two-step atom transfer radical polymerization

The synthesis of ABC triblock copolymer poly(ethylene oxide)-block-poly(methyl methacrylate)-block-polystyrene (PEO-b-PMMA-b-PS) via atom transfer radical polymerization (ATRP) is reported. First, a PEO-Br macroinitiator was synthesized by esterification of PEO with 2-bromoisobutyryl bromide, which was subsequently used in the preparation of halo-terminated poly(ethylene oxide)-block-poly(methyl methacrylate) (PEO-b-PMMA) diblock copolymers under ATRP conditions. Then PEO-b-PMMA-b-PS triblock copolymer was synthesized by ATRP of styrene using PEO-b-PMMA as a macroinitiator. The structures and molecular characteristics of the PEO-b-PMMA-b-PS triblock copolymers were studied by FT-IR, GPC and ¹H NMR.     

Comparison of hydrogen bonding interaction between PMMA/PMAA blends and PMMA-co-PMAA copolymers

A series of miscible PMMA/PMAA blends and PMMA-co-PMAA copolymers with different compositions were prepared in this study. T_gs of PMMA-co-PMAA copolymers are significantly higher than average values or from the Fox equation. The proton spin-lattice relaxation time in the rotating frame (T_1ρ^H) determined by high resolution solid state ¹³C nuclear magnetic resonance indicates single composition-dependent from all blends and copolymers, implying a good miscibility with chain dynamics on a scale of 1-2 nm. However, T_1ρ^Hs of copolymers are still smaller than those of blends, implying that degrees of homogeneity of copolymers are higher than those of blends. On the basis of Kovacs' free volume theory, the free volume of the copolymer obtained is decreased which is another indication of greater homogeneity of the copolymer than that of the corresponding blend. According to Fourier transform infrared spectroscopy analyses, the above results can be rationalized that the hydrogen bonding interaction of the copolymer is stronger than the blend.     

Dynamic mechanical properties of annealed sulfonated poly(styrene-b-[ethylene/butylene]-b-styrene) block copolymers

Solution cast films of lightly sulfonated styrene-b-[ethylene-co-butylene]-b-styrene, (sSEBS) block copolymers were annealed for various times at 120 °C and thermal transitions are evaluated using dynamic mechanical analysis. Increased annealing time and increase in degree of sulfonation increases T_g for the PS phase while T_g for the EB phase is practically unchanged, and in some cases, there is suggestion of a relaxation due to EB-PS inter-phases. Annealing has a minor effect on the rubbery plateau storage modulus. Thus, annealing primarily alters the PS block phase. EB-PS phase separation appears to be refined with increasing SO₃H content. The region of rubber elasticity extends to higher temperatures with increased degree of sulfonation. A high temperature dynamic mechanical transition that is tentatively attributed to disruption of SO₃H—rich sub-domains within the PS block domains shifts to higher temperature with annealing.     

Self-Assembly structures through competitive interactions of miscible crystalline-amorphous diblock copolymer/homopolymer blends

A series of miscible crystalline-amorphous diblock copolymers, (poly(?-caprolactone)-b-(vinyl phenol), PCL-b-PVPh) were prepared through sequential ring-opening and controlled living free radical (nitroxide-mediated) polymerizations and then blended with poly(vinyl pyrrolidone) (PVP) homopolymer. Specific interactions, miscibility, and self-assembly morphologies mediated by hydrogen bonding interactions of this new A-B/C type blend, were investigated in detail. Micro-phase separation of these miscible PCL-b-PVPh diblock copolymers occurs by blending with PVP through competitive hydrogen bonding interaction in this A-B/C blend. FTIR, XRD, and DSC analyses provide positive evidences that the carbonyl group of PVP is a significantly stronger hydrogen bond acceptor than PCL, thus the PCL block is excluded from the PVPh/PVP miscible phase to form self-assembly structure. ¹³C CP/MAS solid-state NMR spectra provide additional evidence confirming that micro-phase separation occurs in the blend system because of the presence of more than two T_1ρ(H) values for this A-B/C blend system. According to the result of the FTIR and SAXS results, the smaller molecular weight system contains a greater fraction of the hydrogen-bonded carbonyl group, cause indirectly the high degree of phase separation among these blends. In addition, the SAXS profiles possess a sharp primary peak and highly long range ordered reflections q/q^∗ ratios of 1:2:3 at lower PVP content, an indication of the lamellar structure in the blend which is consistent with TEM image. The phase behavior and morphology shifts from lamellar to cylinder structure with further increase in the PVP content.     

Elastic behavior of flexible polyether(urethane-urea) foam materials

Polyether(urethane-urea) foams (PEUU) with varying urea contents and different polyether segments (PPO and PPO-co-PEO (93/7 w/w)) were compacted to transparent solid plaques via compression molding. The thermal, mechanical and elastic properties of the compacted PEUU materials were studied. With increasing urea content, the shear modulus was increased, while the glass transition temperature (T_g) remained low and unaffected. The T_g's of PEEU's with PPO segments were, however, lower than with PPO-co-PEO segments, indicating more mixing of urea segments with PPO-co-PEO. The flow temperatures of both PEUU's were high (∼300 °C) for all compositions. The compression sets, tensile sets and hysteresis energy of the PEUU's were low and increased with urea content. The use of PPO-co-PEO segments resulted in PEEU's with higher compression sets and tensile sets and also more hysteresis. The recovery of the PEUU's showed two relaxation regimes: a fast (elastic) recovery and a slower (viscoelastic) recovery. The recovery of these PEUU's is almost complete giving time.     

Thermosets with core-shell nanodomain by incorporation of core crosslinked star polymer into epoxy resin

Core crosslinked star (CCS) polymers, which have crosslinked poly (divinyl benzene-co-styrene) [P(DVB-St)] core and multiple arms of polystyrene-b-poly(ethylene oxide) diblock copolymer (PEO-b-PS) [denoted as PEO-b-PS/P(DVB-St) CCS], were synthesized via atom transfer radical polymerization(ATRP). PEO-b-PS/P(DVB-St) CCS polymer was spherical with average diameters of scores of nanometers from transmission electron microscopy (TEM) and dynamic light scattering (DLS), and blended with diglycidyl ether of bisphenol (DGEBA) and 4,4′-diamino diphenyl methane (DDM) in tetrahydrofuran (THF). With 5 or 10 wt% PEO-b-PS/P(DVB-St) CCS polymer, spherical core-shell nanodomains with average diameters of 29 or 32 nm were observed from atomic force microscopy (AFM), which were randomly distributed in the resultant thermosets. Considering the difference in miscibility of the epoxy with P(DVB-St) and PEO-b-PS after and before curing reaction, a reaction-induced microphase separation (RIMPS) mechanism was proposed to account for the formation of the core-shell nanodomains in the thermosets. During curing, the RIMPS of PS subchain occurred but was confined by P(DVB-St) core, resulting in formation of thermoplastic PS shell around the crosslinked core. Such core-shell nanodomain could be easily etched away by THF, whereas the control thermosets containing PEO/P(DVB-St) CCS polymer could not be etched by THF. The glass transition temperatures (T_gs) of the epoxy thermosets containing PEO-b-PS/P(DVB-St) CCS polymer were significantly improved compared with pure epoxy thermosets.     

Miscibility and intermolecular specific interactions in blends of poly(hydroxyether of bisphenol A) and poly(4-vinyl pyridine)

The blends of poly(hydroxyether of bisphenol A) (phenoxy) with poly(4-vinyl pyridine) (P4VPy) were investigated by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. The single, composition-dependent glass transition temperature (T_g) was observed for each blend, indicating that the system is completely miscible. The sigmoid T_g-composition relationship is characteristic of the presence of the strong intermolecular specific interactions in the blend system. FTIR studies revealed that there was intermolecular hydrogen bonding in the blends and the intermolecular hydrogen bonding between the pendant hydroxyl groups of phenoxy and nitrogen atoms of pyridine ring is much stronger than that of self-association in phenoxy. To examine the miscibility of the system at the molecular level, the high resolution ¹³C cross-polarization (CP)/magic angle spinning (MAS) together with the high-power dipolar decoupling (DD) NMR technique was employed. Upon adding P4VPy to the system, the chemical shift of the hydroxyl-substituted methylene carbon resonance of phenoxy was observed to shift downfield in the ¹³C CP/MAS spectra. The proton spin-lattice relaxation time T₁(H) and the proton spin-lattice relaxation time in the rotating frame T_1ρ(H) were measured as a function of the blend composition. In light of the proton spin-lattice relaxation parameters, it is concluded that the phenoxy and P4VPy chains are intimately mixed on the scale of 20-30 Å.     

Effect of hydrophobic polystyrene microphases on temperature-responsive behavior of poly(N-isopropylacrylamide) hydrogels

Reversible addition-fragmentation chain transfer polymerization was employed to prepare the crosslinked poly(N-isopropylacrylamide)-graft-polystyrene networks (PNIPAAm-g-PS). Due to the immiscibility of PNIPAAm with PS, the crosslinked PNIPAAm-g-PS copolymers displayed the microphase-separated morphology. While the PNIPAAm-g-PS copolymer networks were subjected to the swelling experiments, it is found that the PS block-containing PNIPAAm hydrogels significantly exhibited faster response to the external temperature changes according to swelling, deswelling, and reswelling experiments than the conventional PNIPAAm hydrogels. The improved thermo-responsive properties of hydrogels have been interpreted on the basis of the formation of the specific microphase-separated morphology in the hydrogels, i.e., the PS blocks pendent from the crosslinked PNIPAAm networks were self-assembled into the highly hydrophobic nanodomains, which behave as the microporogens and thus promote the contact of PNIPAAm chains and water. The self-organized morphology in the hydrogels was further confirmed by photon correlation spectroscopy (PCS). The PCS shows that the linear model block copolymers of PNIPAAm-g-PS networks were self-organized into micelle structures, i.e., the PS domains constitute the hydrophobic nanodomains in PNIPAAm-g-PS networks.     

Synthesis and characterization of degradable triarm low unsaturated poly(propylene oxide)‐block‐polylactide copolymers

A series of novel degradable triarm poly(propylene oxide)‐block‐polylactide (PPO‐b‐PLA) copolymers was synthesized by ring‐opening polymerization of L ‐lactide (LLA) or D ,L ‐lactide (DLLA) using low unsaturated PPO triols as macromolecular initiator. The chemical structures of the resulting copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance (¹H‐NMR) spectroscopy. Combination of FTIR, GPC, and NMR results confirmed the formation of PPO‐b‐PLA copolymers. One glass transition was observed by differential scanning calorimetry (DSC), suggesting good miscibility between PPO and PLA segments in the copolymers. DSC and wide‐angle X‐ray diffraction demonstrated that PPO‐b‐PLLA copolymers were semicrystalline materials, and the crystallinity increased with increasing the PLLA content. In contrast, PPO‐b‐PDLLA copolymers were totally amorphous. The PPO‐b‐PLA copolymers exhibited improved thermal stability when compared with PPO polyols according to thermogravimetric analysis. The thermal degradation behavior of the copolymers depended on the composition. Polyurethane foams were prepared by crosslinking PPO and PPO‐b‐PLA copolymers using isocyanate. Alkaline degradation of the foams was investigated in 10 wt/vol % NaOH at 80°C. The results show that the novel PPO‐b‐PLA copolymers could be promising as degradable polymeric materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Miscibility with positive deviation in Tg-composition relationship in blends of poly(2-vinyl pyridine)-block-poly(ethylene oxide) and poly(p-vinyl phenol)

Phase behavior and miscibility with positive deviation from linear T_g-composition relationship in a copolymer/homopolymer blend system, poly(2-vinyl pyridine)-block-poly(ethylene oxide) (P2VP-b-PEO)/poly(p-vinyl phenol) (PVPh), were investigated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and solid-state ¹³C nuclear magnetic resonance (¹³C NMR), optical microscopy (OM), and scanning electron microscopy (SEM). Optical and electron microscopy results as well as NMR proton spin-lattice relaxation times in laboratory frame () all confirmed the miscibility as judged by the T_g criterion using DSC. In comparison to the literature result on a homopolymer/homopolymer blend of P2VP/PVPh, fitting with the Kwei equation on the T_g-composition relationship for the block-copolymer/homopolymer blend of P2VP-b-PEO/PVPh blend system yielded a smaller q value (q = 120) for P2VP-b-PEO/PVPh than that for P2VP/PVPh blend (q = 160). The FT-IR and ¹³C NMR results revealed hydrogen-bonding interactions between the pendant pyridine group of P2VP-b-PEO and phenol unit in PVPh, which is responsible for the noted positive deviation of the T_g-composition relationship. Comparison of the shifts of hydroxyl IR absorbance band, reflecting the average strength of H-bonding, indicates a decreasing order of P2VP/PVPh > P2VP-b-PEO/PVPh > PEO/PVPh blends. The PEO block in the copolymer segment tends to defray the interaction strength in the P2VP-b-PEO/PVPh blends because of relative weaker interaction between PEO and PVPh than that between P2VP and PVPh pairs. A comparative ternary (P2VP/PEO)/PVPh blend was also studied as the controlling experiments for comparison to the P2VP-b-PEO/PVPh blend. The thermal behavior and interaction strength in (P2VP/PEO)/PVPh ternary blends are discussed with those in the P2VP-b-PEO/PVPh copolymer/homopolymer blend.     

Fast physical drying,high water and salt resistant coatings from non-drying vegetable oil

This paper reports fast physical drying, high water and salt resistances of coating materials from non-drying palm oleic acid. Short oil-length alkyd was synthesized and copolymerized with methyl methacrylate. Three copolymers of the alkyd and methyl methacrylate with different alkyd/MMA ratios were prepared via free radical polymerization. The copolymers were characterized by FTIR and H NMR spectroscopy, and glass transition temperatures (T_g) were measured by DSC. The decreasing amount of alkyd was noticed to increasing conversion and T_g. The overall thermal stability has increased with higher amount of alkyd in the copolymer. Moreover, incorporation of alkyd has improved the adhesion and film hardness of the coatings.     

The effect of different lithium salts on conductivity of comb-like polymer electrolyte with chelating functional group

The behaviors of lithium ions in a comb-like polymer electrolyte with chelating functional group complexed with LiCF₃SO₃, LiBr and LiClO₄ were characterized by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, AC impedance, and ¹³C solid-state NMR measurement. The comb-like copolymer was synthesized from poly(ethylene glycol) methyl ether methacrylate (PEGMEM) and (2-methylacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester) (GMA-IDA). FT-IR spectra reveal the interactions of Li⁺ ions with both the ether oxygen of the PEGMEM and the nitrogen atom of the GMA-IDA segments. FT-IR spectra also indicate an increasing anion-cation association consistent with increasing LiCF₃SO₃ concentrations. Moreover, the ¹³C solid-state NMR spectra for the carbons attached to the ether oxygen atoms exhibited significant line broadening and a slight upfield chemical shift when the dopant was added to the polymer. These findings indicate coordination between the Li cation and the ether oxygens in the PEG segment. T_g and T_d of copolymers doped with salts clearly increase, as shown by DSC and TGA measurements. These results indicate the interactions of Li⁺ with both PEGMEM and GMA-IDA segments form transient cross-links inside the copolymers. The Vogel-Tamman-Fulcher (VTF)-like behavior of conductivity implies the coupling of the charge carriers with the segmental motion of the polymer chain in this study. The maximum conductivity of copolymers relates to the composition of the copolymers and the concentration of doping lithium ions. In summary, the GMA-IDA unit in the copolymer promotes the dissociation of the lithium salt, the mechanical strength and the conductivity of the polyelectrolyte.     

Synthesis and characterization of copolymers with the same proportions of polystyrene and poly(ethylene oxide) compositions but different connection sequence by the efficient Williamson reaction

The AB type diblock PS‐b‐PEO and ABA type triblock PS‐b‐PEO‐b‐PS copolymers containing the same proportions of polystyrene (PS) and poly(ethylene oxide) (PEO) but different connection sequence were synthesized and investigated. Using the sequential living anionic polymerization and ring‐opening polymerization mechanisms, diblock PS‐b‐PEO copolymers with one hydroxyl group at the PEO end were obtained. Then, using the classic and efficient Williamson reaction (realized in a ‘click’ style), triblock PS‐b‐PEO‐b‐PS copolymers were achieved by a coupling reaction between hydroxyl groups at the PEO end of PS‐b‐PEO. The PS‐b‐PEO and PS‐b‐PEO‐b‐PS copolymers were well characterized by ¹H NMR spectra and SEC measurements. The critical micelle concentration (CMC) and thermal behaviors were also investigated by steady‐state fluorescence spectra and DSC, respectively. The results showed that, because the PEO segment in triblock PS‐b‐PEO‐b‐PS was more restricted than that in diblock PS‐b‐PEO copolymer, the former PS‐b‐PEO‐b‐PS copolymer always gave higher CMC values and lower crystallization temperature (T_c), melting temperature (T_m) and degree of crystallinity (X_c) parameters. © 2015 Society of Chemical Industry