Salt‐induced microphase separation of amorphous dendritic poly(ethylene oxide)‐block‐linear polystyrene copolymers

We prepared two block copolymers 1 and 2 consisting of a third‐generation dendron with poly(ethylene oxide) (PEO) peripheries and a linear polystyrene (PS) coil. The PS molecular weights were 2000 g/mol and 8000 g/mol for 1 and 2 , respectively. The differential scanning calorimetry (DSC) data indicated that neither of the block copolymers showed glass transition, implying that there was no microphase separation between the PEO and PS blocks. However, upon doping the block copolymers with lithium triflate (lithium concentration per ethylene oxide unit = 0.2), two distinct glass transitions were seen, corresponding to the salt‐doped PEO and PS blocks, respectively. The morphological analysis using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) demonstrated that a hexagonal columnar morphology was induced in salt‐doped sample 1‐Li⁺ , whereas the other sample ( 2‐Li⁺ ) with a longer PS coil revealed a lamellar structure. In particular, in the SAXS data of 2‐Li⁺ , an abrupt reduction in the lamellar thickness was observed near the PS glass transition temperature (T_g), in contrast to the SAXS data for 1‐Li⁺ . This reduction implies that there is a lateral expansion of the molecular section in the lamellar structure, which can be interpreted by the conformational energy stabilization of the long PS coil above T_g. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2372–2376, 2010     

Synthesis and characterization of side‐chain liquid crystalline ABC triblock copolymers with p‐methoxyazobenzene moieties by atom transfer radical polymerization

A series of novel side‐chain liquid crystalline ABC triblock copolymers composed of poly(ethylene oxide) (PEO), polystyrene (PS), and poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PMMAZO) were synthesized by atom transfer radical polymerization (ATRP) using CuBr/1,1,4,7,7‐pentamethyldiethylenetriamine (PMDETA) as a catalyst system. First, the bromine‐terminated diblock copolymer poly(ethylene oxide)‐block‐polystyrene (PEO‐PS‐Br) was prepared by the ATRP of styrene initiated with the macro‐initiator PEO‐Br, which was obtained from the esterification of PEO and 2‐bromo‐2‐methylpropionyl bromide. An azobenzene‐containing block of PMMAZO with different molecular weights was then introduced into the diblock copolymer by a second ATRP to synthesize the novel side‐chain liquid crystalline ABC triblock copolymer poly(ethylene oxide)‐block‐polystyrene‐block‐poly[6‐(4‐methoxy‐4′‐oxy‐azobenzene) hexyl methacrylate] (PEO‐PS‐PMMAZO). These block copolymers were characterized using proton nuclear magnetic resonance (¹H NMR) and gel permeation chromatograph (GPC). Their thermotropic phase behaviors were investigated using differential scanning calorimetry (DSC) and polarized optical microscope (POM). These triblock copolymers exhibited a smectic phase and a nematic phase over a relatively wide temperature range. At the same time, the photoresponsive properties of these triblock copolymers in chloroform solution were preliminarily studied. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4442–4450, 2008     

Crystallization and melting of poly(glycerol adipate)‐based graft copolymers with single and double crystallizable side chains

The crystallization and melting behavior of a series of poly(glycerol adipate) (PGA) based graft copolymers with either poly(ε‐caprolactone) (PCL), poly(ethylene oxide) (PEO), or PCL‐b‐PEO diblock copolymer side chains (i.e., PGA‐g‐PCL, PGA‐g‐PEO, and PGA‐g‐(PCL‐b‐PEO)) was studied using polarized light optical microscopy (POM), differential scanning calorimetry (DSC), small‐angle X‐ray scattering (SAXS), and wide‐angle X‐ray diffraction (WAXD). These results were compared with the behavior of the corresponding linear analogs (PEO, PCL, and PCL‐b‐PEO). POM revealed that spherulitic morphology was retained after grafting. However, spherulite radius as well as radial growth rate was significantly smaller in the graft copolymers. Evaluation of isothermal crystallization kinetics by means of the Avrami theory revealed that the nucleation density was much higher in the graft copolymers. The DSC results indicated that the degree of crystallinity decreased strongly upon grafting while the melting temperatures of PGA‐g‐PCL and PGA‐g‐PEO were found to be close to the values of neat PCL and PEO, respectively. This was attributed to the absence of specific thermodynamic interactions, and, additionally, to lamella thicknesses being similar to those of the homopolymers. The latter point was confirmed by SAXS measurements. In case of PCL‐b‐PEO diblock copolymers and PGA‐g‐(PCL‐b‐PEO) graft copolymers, the crystallization behavior and thus the resulting lamellar morphology is more complex, and a suitable model was developed based on a combination of DSC, WAXD, and SAXS data. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1581–1591     

Micro‐phase‐separation behavior of amphiphilic polyurethanes involving poly(ethylene oxide) and poly(tetramethylene oxide)

The temperature dependence of thermal, morphological, and rheological properties of amphiphilic polyurethanes was examined with differential scanning calorimetry (DSC), wide‐angle X‐ray scattering (WAXS), small‐angle X‐ray scattering (SAXS), rheological measurements, and Fourier transform infrared spectroscopy. Multiblock (MPU) and triblock (TPU) polyurethanes were synthesized with two crystallizable segments—poly(ethylene oxide) (PEO) as a hydrophilic block and poly(tetramethylene oxide) (PTMO) as a hydrophobic block. DSC and WAXS measurements demonstrated that the microphase of MPUs in the solid state is dominantly affected by the PEO crystalline phase. However, high‐order peaks were not observed in the SAXS measurements because the crystallization of the PEO segments in MPUs was retarded by poor sequence regularity. The microphase in the melt state was induced by the hydrogen bonding between the N? H group of hexamethylene diisocyanate linkers and the ether oxygen of PEO or PTMO blocks. As the temperature increased, the smaller micro‐phase‐separated domains were merged into the larger domains, and the liquidlike ordering was eventually disrupted because of the weakening hydrogen bonding. However, the fully homogeneous state of an MPU with a molar ratio of 5/5 PEO/PTMO (MPU55) was not confirmed even at much higher temperatures with both SAXS and rheological measurements. However, the SAXS patterns of TPU showed weak but broad second‐order peaks below the melting temperature of the PEO block. Compared with MPU55, the ordering of the TPU crystalline lamellar stacks was enhanced because of the high sequence regularity and the low hydrogen‐bonding density. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2365–2374, 2003     

Synthesis and morphology of model PS‐b‐PDMS copolymers

True model linear poly(styrene‐b‐dimethylsiloxane) PS‐b‐PDMS copolymers were synthesized by using sequential addition of monomers and anionic polymerization (high‐vacuum techniques), employing the most recent experimental procedures that allow the controlled polymerization of each monomer to obtain blocks with controlled molar masses. The model diblock copolymers obtained were analyzed by using different techniques, such as size‐exclusion chromatography, ¹H NMR, Fourier transform infrared spectroscopy, small angle X‐rays scattering (SAXS), and wide angle X‐rays scattering (WAXS). The PS‐b‐PDMS copolymers obtained showed narrow molar mass distribution and variable PDMS content, ranging from 2 up to 55 wt %. Compacted powder samples were investigated by SAXS to reveal their structure and morphology changes on thermal treatment in the interval from 30 to 200 °C. The sample with the highest PDMS content exhibits a lamellar morphology, whereas two other samples show hexagonally packed cylinders of PDMS in a PS matrix. For the lowest PDMS content samples, the SAXS pattern corresponds to a disordered morphology and did not show any changes on thermal treatment. Detailed information about the morphology of scattering domains was obtained by fitting the SAXS scattering curves. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3119–3127, 2010     

Crystallization and morphology of poly(ethylene oxide‐b‐lactide) crystalline–crystalline diblock copolymers

The crystallization behaviors and morphology of asymmetric crystalline–crystalline diblock copolymers poly(ethylene oxide‐lactide) (PEO‐b‐PLLA) were investigated using differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), and microscopic techniques (polarized optical microscopy (POM) and atomic force microscopy (AFM)). Both blocks of PEO₅‐b‐PLLA₁₆ can be crystallized, which was confirmed by WAXD, while PEO block in PEO₅‐b‐PLLA₃₀ is difficult to crystallize because of the confinement induced by the high glass transition temperature and crystallization of PLLA block with the microphase separation of the block copolymer. Comparing with the crystallization and morphology of PLLA homopolymer and differences between the two copolymers, we studied the influence of PEO block and microphase separation on the crystallization and morphology of PLLA block. The boundary temperature (T_b) was observed, which distinguishes the crystallization into high‐ and low‐temperature ranges, the growth rate and morphology were quite different between the ranges. Crystalline morphologies including banded spherulite, dendritic crystal, and dense branching in PEO₅‐b‐PLLA₁₆ copolymer were formed. The typical morphology of dendritic crystals including two different sectors were observed in PEO₅‐b‐PLLA₃₀ copolymer, which can be explained by secondary nucleation, chain growth direction, and phase separation between the two blocks during the crystallization process. Lozenge‐shaped crystals of PLLA with screw dislocation were also observed employing AFM, but the crystalline morphology of PEO block was not observed using microscopy techniques because of its small size. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1400–1411, 2008     

Synthesis and Characterization of Crystalline Styrene‐b‐(Ethylene‐co‐Butylene)‐b‐Styrene Triblock Copolymers

By merit of dual catalysis of the cationic rare‐earth complex [(η⁵‐Flu‐CH₂‐Py)Ho(CH₂SiMe₃)₂(THF) (Flu = fluorenyl, Py = pyridyl) for the living polymerizations of butadiene (BD) and styrene (St), the crystalline styrene‐butadiene‐styrene (SBS) triblock copolymers consisting of elastic polybutadiene (PBD) sequences with suitable 1,4 regularity (about 70%) and crystalline syndiotactic polystyrene (sPS, [rrrr] > 99%) sequences were successfully synthesized through sequential addition of St, BD, and St monomers. The catalytic system showed high polymerization activities for St and BD in a controlled manner. The crystalline styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) triblock copolymers were obtained by hydrogenation of the above SBS copolymers. The observation of a strong endothermic peak at 266 °C in their differential scanning calorimetry (DSC) curves confirmed the existence of the sPS blocks in the crystalline SEBS different from the industrial product Kraton SEBS‐1652. Thermal degradation temperature of the crystalline SEBS (418 ± 2 °C) indicated the well thermostability and process window of this polymer. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 55, 1243–1249     

β‐Lactam functionalized poly(isoprene‐b‐ethylene oxide) amphiphilic block copolymers

Amphiphilic block copolymers containing β‐lactam groups on the polyisoprene block were synthesized from poly(isoprene‐b‐ethylene oxide) (IEO) diblock copolymer precursors, prepared by anionic polymerization. β‐Lactam functionalization was achieved via reaction of the polyisoprene (PI) block with chlorosulfonyl isocyanate and subsequent reduction. The resulting block copolymers were molecularly characterized by SEC, FTIR, and NMR spectroscopies and DSC. Functionalization was found to proceed in high yields, altering the solubility properties of the PI block and those of the functionalized diblocks. Hydrogen bond formation is assumed to be responsible for the decreased crystallinity of the poly(ethylene oxide) block (PEO) in the bulk state as indicated by DSC measurements. The self‐assembly behavior of the β‐lactam functionalized poly(isoprene‐b‐ethylene oxide) copolymers (LIEO) in aqueous solutions was studied by dynamic light scattering (DLS), static light scattering (SLS), fluorescence spectroscopy, and atomic force microscopy (AFM). Nearly spherical loose aggregates were formed by the LIEO block copolymers, having lower aggregation numbers and higher cmc values compared to the IEO precursors, as a result of the increased polarity of the β‐lactam rings incorporated in the PI blocks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 24–33, 2010     

Supramolecular polyseudorotaxanes formation between star‐block copolymer and α‐cyclodextrin: From outer block to diblock inclusion complexation

A series of star‐block poly(L ‐lactide)‐b‐poly(ethylene oxide) (SPLLA‐b‐PEO) copolymers were synthesized by ring‐opening polymerization (ROP) and DCC chemistry. The inclusion complexes of SPLLA‐b‐PEO copolymers and α‐cyclodextrin (α‐CD) were prepared with two different methods. FTIR, ¹H NMR, WAXD, DSC, and TGA indicate that α‐CD only can be threaded onto PEO blocks in inclusion complexes of α‐CD‐SPLLA‐b‐PEO1.1K‐a, α‐CD‐SPLLA‐b‐PEO2K‐a, and α‐CD‐SPLLA‐b‐PEO5K‐a formed without heating and ultrasonication, and can be threaded onto both PLLA and PEO blocks in inclusion complexes of α‐CD‐SPLLA‐b‐PEO1.1K‐b, α‐CD‐SPLLA‐b‐PEO2K‐b, and α‐CD‐SPLLA‐b‐PEO5K‐b formed with heating and ultrasonication. Namely, α‐CDs can be threaded onto PEO blocks and the flanking bulky PLLA blocks of star‐block copolymers to form stable polyseudorotaxanes with heating method and ultrasonication to conquer the activation energy barrier of the inclusion complexation between bulky PLLA and α‐CD and the effect of the steric hindrance of star‐block copolymers. With the alteration of preparing methods, the inclusion complexes of α‐CD with the outer PEO block or PEO and PLLA blocks were obtained successfully. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2754–2762, 2009     

Synthesis and characterization of model polybutadiene‐1,4‐b‐polydimethylsiloxane‐b‐polybutadiene‐1,4 copolymers

Model copolymers of poly(butadiene) (PB) and poly(dimethylsiloxane) (PDMS), PB‐b‐PDMS‐b‐PB, were synthesized by sequential anionic polymerization (high vacuum techniques) of 1,3‐butadiene and hexamethylciclotrisiloxane (D₃) on sec‐BuLi followed by chlorosilane‐coupling chemistry. The synthesized copolymers were characterized by nuclear magnetic resonance (¹H NMR), size‐exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). SEC and ¹H NMR results showed low polydispersity indexes (M_w/M_n) and variable siloxane compositions, whereas DSC and TGA experiments indicated that the thermal stability of the triblock copolymers depends on the PDMS composition. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2726–2733, 2007     

Synthesis and bulk characterization of new P(CB‐b‐S) diblock copolymers

Strongly asymmetric chlorinated polybutadiene‐b‐polystyrene, [P((CB)_x‐b‐(PS)_y)] diblock copolymers with increasing x/(x + y) ratios (up to 5.2 mol %) have been synthesized by the selective chlorination of the polybutadiene (PB) block in solution. Chlorination has been performed in anhydrous dichloromethane added with an antioxidant [2,2′‐methylenebis‐(6‐tert‐butyl‐4‐methyl‐phenol)], at −50°C, under a continuous Ar flow and in the dark. Under the optimized experimental conditions, the PB chlorination is not complete, but the PS block is left unmodified. Even in the presence of a large chlorine excess (Cl₂/butene unit molar ratio of 2.5), the experimental degree of chlorination of homo PB does not exceed 85%. The chlorinated copolymers have been characterized by ¹H‐NMR, IR spectroscopy, size‐exclusion chromatography, and elemental analysis. The chlorinated copolymers have also been studied by DSC and SAXS after annealing at 150°C. Although at this temperature the parent homopolymers are immiscible, no microphase separation has been observed for the block copolymers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 233–244, 1999     

Templated nanostructured PS‐b‐PEO nanotubes

With anodic aluminum oxide (AAO) membranes as wetting templates, nanotubes of the cylinder‐forming polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) copolymer were generated. The PS‐b‐PEO solution was introduced into the cylindrical nanopores of an AAO membrane by capillary force and polymeric nanotubes formed after solvent evaporation. Because of the water solubility of the cylindrical PEO microdomains and the orientation of the cylindrical PEO microdomains with respect to the nanotube walls, the nanotubes were permeable to aqueous media. PS‐b‐PEO nanotubes were also prepared on the interior walls of amorphous carbon nanotubes (a‐CNTs). Because of the unique water permeability of the PEO microdomains, an avenue for functionalizing the interior of the a‐CNTs is enabled. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2912–2917, 2007     

The influence of variant PE‐b‐PEO segments on physical properties of LLDPE graft copolymers

A method was adopted to fix a series of polymers of PE‐b‐PEO with different PEO/PE segments on the chains of LLDPE. Maleic anhydride (MA) reacting with hydroxyl group of PE‐b‐PEO (mPE‐b‐PEO) was used as the intermediate. The structures of intermediates and graft copolymers were approved by ¹H NMR and FTIR. XPS analysis revealed a great amount of oxygen on the surface of grafted copolymers although the end group of PEO was fixed on the LLDPE chains through MA. Thermal properties of the graft copolymers as determined by differential scanning calorimetry (DSC) showed that PE segments in the grafted monomers could promote the heterogeneous nucleation of the polymer, increase T_c, and crystal growth rate. While the amorphous PEO segments which attached to the crystalline PE segments in LLDPE, impaired their ability to fit the crystal lattice, and depressed the crystallization of LLDPE backbones. In this study, it was also verified through the dynamic rheological data that increasing M_n of grafted monomers significantly increased the complex viscosity and enhanced the shear‐thinning behavior. Long‐branched chains formed by grafted monomers enhanced the complex moduli (G′ and G″) value and retarded relaxation rate. However, there were little influence on the rheological properties when increasing the amounts of PEO segments (or decreasing PE segments) of grafted monomers with similar molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 506–515, 2008     

Thermal monitoring of morphology in triblock terpolymers with crystallizable blocks

The bulk morphology of poly(1,4‐butadiene)–block–polystyrene–block–poly (ethylene oxide) (PB‐b‐PS‐b‐PEO) and polyethylene–block–polystyrene–block–poly (ethylene oxide) (PE‐b‐PS‐b‐PEO) triblock terpolymers is analyzed under a thermal protocol. This allows the investigation of the morphology during the occurrence of thermal transitions, such as crystallization and melting, which is a neat way of studying the competition between microphase separation and crystallization for the morphology formation. Only one of the studied systems presented a morphological transition upon melting of the PEO and the PE blocks, attributed to the crystallization of the PE block in finite interconnected domains. All the other systems presented no morphological transitions during the thermal scan. The results prove that the crystallization only disrupt the microphases generated in the molten state under very specific circumstances for these block copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3197–3206, 2007     

Highly ordered nanoporous thin films by blending of PSt‐b‐PMMA block copolymers and PEO additives as structure directing agents

Herein, we present a simple method for producing nanoporous templates with a high degree of lateral ordering by self‐assembly of block copolymers. A key feature of this approach is control of the orientation of polymeric microdomains through the use of hydrophilic additives as structure directing agents. Incorporation of hydrophilic poly(ethylene oxide) (PEO) moieties into poly(styrene‐b‐methyl methacrylate) (PSt‐b‐PMMA) diblock copolymers gives vertical alignment of PMMA cylinders on the substrate after solvent annealing. Because of the miscibility between PEO and PMMA, PEO additives were selectively positioned within PMMA microdomains and by controlling the processing conditions, it was found that ordering of PSt‐b‐PMMA diblock copolymers could be achieved. The perpendicular orientation of PMMA cylinders was achieved by increasing the molecular size of the PEO additives leading to an increased hydrophilicity of the PMMA domains and consequently to control the orientation of microdomains in PSt‐b‐PMMA block copolymer thin films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8041–8048, 2008     

Annealing effect on performance and morphology of photovoltaic devices based on poly(3‐hexylthiophene)‐b‐poly(ethylene oxide)

Novel block copolymers, poly(3‐hexylthiophene)‐b‐poly(ethylene oxide) (P3HT‐b‐PEO) were synthesized via Suzuki coupling reaction of P3HT and PEO homopolymers. The copolymers were characterized by NMR, gel permeation chromatography, differential scanning calorimeter, and UV–vis measurements. A series of devices based on the block copolymers with a fullerene derivative were evaluated after thermal or solvent annealing. The device using P3HT‐b‐PEO showed higher efficiency than using P3HT blend after thermal annealing. Phase‐separated structures in the thin films of block copolymer blends were investigated by atomic force microscopy to clarify the relationship between morphologies constructed by annealing and the device performance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Poly(ethylene imine)‐graft‐poly(ethylene oxide) brush‐like copolymers: Preparation,thermal properties,and selective supramolecular inclusion complexation with α‐cyclodextrin

Poly(ethylene imine)‐graft‐poly(ethylene oxide) (PEI‐g‐PEO) copolymers were synthesized via Michael addition reaction between acryl‐terminated poly(ethylene oxide) methyl ether (PEO) and poly(ethylene imine) (PEI). The brush‐like copolymers were characterized by means of Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. It is found that the crystallinity of the PEO side chains in the copolymers remained unaffected by the PEI backbone whereas the crystal structure of PEO side chains was altered to some extent by the PEI backbone. The crystallization behavior of PEO blocks in the copolymers suggests that the bush‐shaped copolymers are microphase‐separated in the molten state. The PEO side chains of the copolymers were selectively complexed with α‐cyclodextrin (α‐CD) to afford hydrophobic side chains (i.e., PEO/α‐CD inclusion complexes). The X‐ray diffraction (XRD) shows that the inclusion complexes (ICs) of the PEO side chains displayed a channel‐type crystalline structure. It is identified that the stoichiometry of the inclusion complexation of the PEI‐g‐PEO with α‐CD is close to that of the control PEO with α‐CD. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2296–2306, 2008     

Hydrophilic–hydrophobic AB diblock copolymers containing poly(trimethylene carbonate) and poly(ethylene oxide) blocks

AB‐type block copolymers with poly(trimethylene carbonate) [poly(TMC); A] and poly(ethylene oxide) [PEO; B; number‐average molecular weight (M_n) = 5000] blocks [poly(TMC)‐b‐PEO] were synthesized via the ring‐opening polymerization of trimethylene carbonate (TMC) in the presence of monohydroxy PEO with stannous octoate as a catalyst. M_n of the resulting copolymers increased with increasing TMC content in the feed at a constant molar ratio of the monomer to the catalyst (monomer/catalyst = 125). The thermal properties of the AB diblock copolymers were investigated with differential scanning calorimetry. The melting temperature of the PEO blocks was lower than that of the homopolymer, and the crystallinity of the PEO block decreased as the length of the poly(TMC) blocks increased. The glass‐transition temperature of the poly(TMC) blocks was dependent on the diblock copolymer composition upon first heating. The static contact angle decreased sharply with increasing PEO content in the diblock copolymers. Compared with poly(TMC), poly(TMC)‐b‐PEO had a higher Young's modulus and lower elongation at break. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4819–4827, 2005     

Synthesis and self‐assembly morphologies of amphiphilic multiblock copolymers [poly(ethylene oxide)‐b‐polystyrene]n via trithiocarbonate‐embedded PEO macro‐RAFT agent

An amphiphilic multiblock copolymer [poly(ethylene oxide)‐b‐polystyrene]_n [(PEO‐b‐PS)_n] is synthesized by using trithiocarbonate‐embedded PEO as macro‐RAFT agent. PEO with four inserted trithiocarbonate (M_n = 9200 and M_w/M_n = 1.62) groups is prepared first by condensation of α, ω‐dihydroxyl poly(ethylene oxide) with S, S′‐Bis(α, α′‐dimethyl‐α″‐acetic acid)‐trithiocarbonate (BDATC) in the presence of pyridine, then a series of goal copolymers with different St units (varied from 25 to 218 per segment) are obtained by reversible addition‐fragmentation chain transfer (RAFT) polymerization. The synthesis process is monitored by size exclusion chromatography (SEC), ¹H NMR and FT‐IR. The self‐assembled morphologies of the copolymers are strongly dependent of the length of PS block chains when the chain length of PEO is fixed, some new morphologies as large leaf‐like aggregates (LLAs), large octopus‐like aggregates (LOAs), and coarse‐grain like micelles (CGMs) are observed besides some familiar aggregates as large compound vesicles (LCVs), lamellae and rods, and the effect of water content on the morphologies is also discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6071–6082, 2006     

Lithium‐Salt‐Containing High‐Molecular‐Weight Polystyrene‐block‐Polyethylene Oxide Block Copolymer Films

Ionic conductivity in relation to the morphology of lithium‐doped high‐molecular‐weight polystyrene‐block‐polyethylene oxide (PS‐b‐PEO) diblock copolymer films was investigated as solid‐state membranes for lithium‐ion batteries. The tendency of the polyethylene (PEO) block to crystallize was highly suppressed by increasing both the salt‐doping level and the temperature. The PEO crystallites completely vanished at a salt‐doping ratio of Li/EO>0.08, at which the PEO segments were hindered from entering the crystalline unit of the PEO chain. A kinetically trapped lamella morphology of PS‐b‐PEO was observed, due to PEO crystallization. The increase in the lamella spacing with increasing salt concentration was attributed to the conformation of the PEO chain rather than the volume contribution of the salt or the previously reported increase in the effective interaction parameter. Upon loading the salt, the PEO chains changed from a compact/highly folded conformation to an amorphous/expanded‐like conformation. The ionic conductivity was enhanced by amorphization of PEO and thereby the mobility of the PEO blocks increased upon increasing the salt‐doping level.