Facile synthesis of core‐surface crosslinked nanoparticles by interblock RAFT polymerization

A new, efficient method for synthesizing stable nanoparticles with poly(ethylene oxide) (PEO) functionalities on the core surface, in which the micellization and crosslinking reactions occur in one pot, has been developed. First, amphiphilic PEO‐b‐PS copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization of styrene using (PEO)‐based trithiocarbonate as a macro‐RAFT agent. The low molecular weight PEO‐b‐PS copolymer was dissolved in isopropyl alcohol where the block copolymer self‐assembled as core‐shell micelles, and then the core‐shell interface crosslink was performed using divinylbenzene as a crosslinking agent and 2,2′‐azobisisobutyronitrile as an initiator. The design of the amphiphilic RAFT agent is critical for the successful preparation of core‐shell interface crosslinked micellar nanoparticles, because of RAFT functional groups interconnect PEO and polystyrene blocks. The PEO functionality of the nanoparticles surface was confirmed by ¹H NMR and FTIR. The size and morphology of the nanoparticles was confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic laser light scattering analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Single Lithium‐Ion Conducting Polymer Electrolytes Based on a Super‐Delocalized Polyanion

A novel single lithium‐ion (Li‐ion) conducting polymer electrolyte is presented that is composed of the lithium salt of a polyanion, poly[(4‐styrenesulfonyl)(trifluoromethyl(S‐trifluoromethylsulfonylimino)sulfonyl)imide] (PSsTFSI^?), and high‐molecular‐weight poly(ethylene oxide) (PEO). The neat LiPSsTFSI ionomer displays a low glass‐transition temperature (44.3 °C; that is, strongly plasticizing effect). The complex of LiPSsTFSI/PEO exhibits a high Li‐ion transference number (t_Li⁺=0.91) and is thermally stable up to 300 °C. Meanwhile, it exhibits a Li‐ion conductivity as high as 1.35×10^?4 S cm^?1 at 90 °C, which is comparable to that for the classic ambipolar LiTFSI/PEO SPEs at the same temperature. These outstanding properties of the LiPSsTFSI/PEO blended polymer electrolyte would make it promising as solid polymer electrolytes for Li batteries.     

Single-ion and salt conductor polymer electrolytes based on poly(4-vinylpyridine) quaternized with poly(ethylene oxide) side chains

A new type of single-ion conductor with fixed cation was synthesized by spontaneous anionic polymerization of 4-vinylpyridine in the presence of short polyethylene oxide ( PEO ) chains as alkylating agents. These comblike polymers have low T_gs and are amorphous with the shorter PEO s. Their conductivities are unaffected by the nature of the anion ( Br ⁻, ClO ₄⁻, and tosylate) and are controlled by the free volume and the mobility of the pendant cation. By comparison of the results at constant free volume, it is shown that the charge density decreases with the increasing length of pendant PEO demonstrating that PEO acts only as a plasticizing agent. Best conductivity results (σ = 10⁻⁵ S cm⁻¹ at 60°C) are obtained with PEO side chains of molecular weight 350. With this sample, the conductivity in the presence of various amounts of added salt (LiTFSI) was studied. A best value of 10⁻⁴ S cm⁻¹ at 60°C is obtained with a molar ratio EO/Li of 10. It is shown that, over the range of examined concentrations (0.2–1.3 mol Li kg⁻¹), the reduced conductivity σ_r/c increases linearly with increasing salt concentration showing that the ion mobility increases continuously. Such behavior is quite unusual since in this concentration range a maximum is generally observed with PEO systems. To interpret this result and by analogy with the behavior of this type of polymer in solution, it is proposed that the conformation of these polymers in the solid state is segregated with the P4VP skeleton more or less confined inside the dense coils surrounded by the PEO side chains. Under the influence of the increasing salt concentration, this microphase separation vanishes progressively: The LiTFSI salt exchanges with the tosylate anions and acts as a miscibility improver agent. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2719–2728, 1997     

Synthesis and characterization of crystalline graft polymer poly(ethylene oxide)‐g‐poly(ɛ‐caprolactone)2 with modulated grafting sites

The graft polymer poly(ethylene oxide)‐g‐poly(?‐caprolactone)₂ (PEO‐g‐PCL₂) with modulated grafting sites was synthesized by the combination of ring‐opening polymerization (ROP) mechanism, efficient Williamson reaction, with thiol–ene addition reaction. First, the precursor of PEO‐Allyl‐PEO with two terminal hydroxyl groups and one middle allyl group was prepared by ROP of EO monomers. Then, the macroinitiator [PEO‐(OH)₂‐PEO]_s was synthesized by sequential Williamson reaction between terminal hydroxyl groups and thiol–ene addition reaction on pendant allyl groups. Finally, the graft polymer PEO‐g‐PCL₂ was obtained by ROP of ?‐CL monomers using [PEO‐(OH)₂‐PEO]_s as macroinitiator. The target graft polymer and all intermediates were well characterized by the measurements of gel permeation chromatography, ¹H NMR, and thermal gravimetric analysis. The crystallization behavior was investigated by the measurements of differential scanning calorimetry, wide‐angle X‐ray diffraction and polarized optical microscope. The results showed that when the PCL content of side chains reached 59.2%, the crystalline structure had been dominated by PCL part and the crystalline structure formed by PEO part can be almost neglected. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2239–2247     

Polyaddition of bifunctional 1,3‐benzoxazine and 2‐methylresorcinol

A polyaddition system consisted of a bifunctional N‐n‐propyl benzoxazine and 2‐methylresorcinol ( MR ) that proceeds at ambient temperature has been developed. In this system, the aromatic ring of MR acted as a bifunctional monomer, reacting with a two equivalent amount of benzoxazine moieties via their ring‐opening reaction. The polyaddition gave the corresponding linear polymer bearing phenolic moieties bridged by Mannich‐type linkage in the main chain. The linear polymer had a high glass transition temperature, which was comparable to that of the linear polybenzoxazine synthesized by the ring‐opening polymerization of a monofunctional N‐n‐propyl benzoxazine. The employment of a bifunctional N‐allyl benzoxazine in the polyaddition system resulted in the formation of the corresponding polymer with allyl pendants, which exhibited improved heat resistance due to its thermally induced crosslinking reaction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3867–3872     

Highly fluorinated low‐molecular‐weight photoresists for optical waveguides

A series of highly fluorinated polymers were synthesized by copolymerization of 2,3,4,5,6‐pentafluorostyrene (PFS) and fluorinated styrene derivate monomer (FSDM). Their chemical structure were confirmed by ¹H NMR, ¹³C NMR, and ¹⁹F NMR spectra. The refractive index and cross‐linking density of the polymers can be tuned and controlled by monitoring the feed ratio of comonomers. A series of negative‐type low‐molecular‐weight fluorinated photoresists (NFPs) were prepared by composing of fluorinated polystyrene derivates (FPSDs), diphenyl iodonium salt as a photoacid generator (PAG) and solvent. The polymer films prepared from NFP by photocuring exhibited excellent chemical resistance and thermal stabilities (T_d ranged from 230.5 to 258.1 °C). A clear negative pattern was obtained through direct UV exposure and chemical development. For waveguides without upper cladding, the propagation loss of the channel waveguides was measured to be 0.25 dB/cm at 1550 nm. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and characterization of thermoresponsive amphiphilic block copolymers incorporating a poly(ethylene oxide‐stat‐propylene oxide) block

Amphiphilic BuO‐(PEO‐stat‐PPO)‐block‐PLA‐OH diblock and MeO‐PEO‐block‐(PEO‐stat‐PPO)‐block‐PLA‐OH triblock copolymers incorporating thermoresponsive poly(ethylene oxide‐stat‐propylene oxide) (PEO‐stat‐PPO) blocks were prepared by ring‐opening polymerization of lactide (LA) initiated by macroinitiators formed from treating BuO‐(PEO‐stat‐PPO)‐OH and MeO‐PEO‐block‐(PEO‐stat‐PPO)‐OH with AlEt₃. MeO‐PEO‐block‐(PEO‐stat‐PPO)‐OH was prepared by coupling MeO‐PEO‐OH and HO‐(PEO‐stat‐PPO)‐OH, followed by chromatographic purification. The cloud points of 0.2% aqueous solutions are between 36 and 46 °C for the diblock copolymers that contain a 50 wt % EO thermoresponsive block and 78 °C for the triblock copolymer that contains a 75 wt % EO thermoresponsive block. Variable temperature ¹H NMR spectra recorded on D₂O solutions of the diblock copolymers display no PLA resonances below the cloud point and fairly sharp PLA resonances above the cloud point, suggesting that desolvation of the thermoresponsive block increases the miscibility of the two blocks. Preliminary characterization of the micelles formed in aqueous solutions of BuO‐(PEO‐stat‐PPO)‐block‐PLA‐OH conducted using laser scanning confocal microscopy and pulsed gradient spin echo NMR point to significant changes in the size of the micellar aggregates as a function of temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5156–5167, 2005     

Synthesis and characterization of polymer electrolytes based on cross‐linked phenoxy‐containing polyphosphazenes

A new method to prepare the polymer electrolytes for lithium‐ion batteries is proposed. The polymer electrolytes were prepared by reacting poly(phosphazene)s (MEEPP) having 2‐(2‐methoxyethoxy)ethoxy and 2‐(phenoxy)ethoxy units with 2,4,6‐tris[bis(methoxymethyl)amino]‐1,3,5‐triazine (CYMEL) as a cross‐linking agent. This method is simple and reliable for controlling the cross‐linking extent, thereby providing a straightforward way to produce a flexible polymer electrolyte membrane. The 6 mol % cross‐linked polymer electrolyte (ethylene oxide unit (EO)/Li = 24:1) exhibited a maximum ionic conductivity of 5.36 × 10^?5 S cm^?1 at 100 °C. The ⁷Li linewidths of solid‐state static NMR showed that the ionic conductivity was strongly related to polymer segment motion. Moreover, the electrochemical stability of the MEEPP polymer electrolytes increased with an increasing extent of cross‐linking, the highest oxidation voltage of which reached as high as 7.0 V. Moreover, phenoxy‐containing polyphosphazenes are very useful model polymers to study the relationship between the polymer flexibility; that is, the cross‐linking extent and the mobility of metal ions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 352–358     

Preparation of poly(ethylene oxide) star polymers and poly(ethylene oxide)–polystyrene heteroarm star polymers by atom transfer radical polymerization

Poly(ethylene oxide) (PEO) star polymer with a microgel core was prepared by atom transfer radical poylmerization (ATRP) of divinyl benzene (DVB) with mono‐2‐bromoisobutyryl PEO ester as a macroinitiator. Several factors, such as the feed ratio of DVB to the initiator, type of catalysts, and purity of DVB, play important roles during star formation. The crosslinked poly(divinyl benzene) (PDVB) core was further obtained by the hydrolysis of PEO star to remove PEO arms. Size exclusion chromatography (SEC) traces revealed the bare core has a broad molecular weight distribution. PEO–polystyrene (PS) heteroarm star polymer was synthesized through grafting PS from the core of PEO star by another ATRP of styrene (St) because of the presence of initiating groups in the core inherited from PEO star. Characterizations by SEC, ¹H NMR, and DSC revealed the successful preparation of the target star copolymers. Scanning electron microscopy images suggested that PEO–PS heteroarm star can form spherical micelles in water/tetrahydrofuran mixture solvents, which further demonstrated the amphiphilic nature of the star polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2263–2271, 2004     

Solid polymer electrolytes. IV. Preparation and characterization of novel crosslinked epoxy‐siloxane polymer complexes as polymer electrolytes

Two series of novel crosslinked siloxane‐based polymers and their complexes with lithium perchlorate (LiClO₄) were prepared and characterized by Fourier transform infrared spectroscopy, solid‐state NMR (¹³C, ²⁹Si, and ⁷Li nuclei), and differential scanning calorimetry. Their thermal stability and ionic conductivity of these complexes were also investigated by thermogravimetric and AC impedance measurements. In these polymer networks, poly(propylene oxide) chains with different molecular weights were introduced through self‐synthesized epoxy‐siloxane precursors cured with two curing agents. The glass‐transition temperature (T_g) of these copolymers is dependent on the length of the ether units. The dissolution of LiClO₄ considerably increases the T_g of the polyether segments. The dependence of the ionic conductivity was investigated as a function of temperature, LiClO₄ concentration, and the molecular weight of the polyether segments. The ion‐transport behavior was affected by the combination of the ionic mobility and number of carrier ions. The ⁷Li solid‐state NMR line shapes of these polymer complexes suggest a significant interaction between Li⁺ ions and the polymer matrix, and temperature‐ and LiClO₄ concentration‐dependent chemical shifts are correlated with ionic conductivity. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1226–1235, 2002     

Synthesis of polyethylene oxide graft polysilylenes and networks based on poly(di‐n‐pentylsilylene/n‐pentyloct‐7‐enyl) copolymers

Poly(dipentylsilylene) copolymers containing n‐pentyl‐n‐oct‐7‐enylsilane units were prepared by reductive coupling of the corresponding dichlorosilanes. Linear high molecular weight and some crosslinked polymer were obtained. The soluble products exhibited optical and thermal properties like poly(dipentylsilylene). Differential scanning calorimetry was used to investigate crystallization and to monitor thermal crosslinking. Vinyl functionalized side chains were hydrosilylated with dipentylsilane and dimethylchlorosilane and crosslinked via the side chains. Hydrosilylation with di‐n‐pentyl(trimethylsiloxypropyl)silane led to a partial hydroxy functionalization of the polysilylene and enabled anionic PEO grafting of the poly(dipentylsilylene). © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2306–2318, 2000     

Lithium Ion Pathway within Li7La3Zr2O12‐Polyethylene Oxide Composite Electrolytes

Polymer–ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high‐performance all‐solid‐state rechargeable batteries. Composite electrolytes have been prepared with cubic‐phase Li₇La₃Zr₂O₁₂ (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high‐resolution solid‐state Li NMR, we are able to track Li ion pathways within LLZO‐PEO composite electrolytes by monitoring the replacement of ⁷Li in the composite electrolyte by ⁶Li from the ⁶Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO‐LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.     

Multiarm star block and multiarm star mixed‐block copolymers via azide‐alkyne click reaction

The synthesis of multiarm star block (and mixed‐block) copolymers are efficiently prepared by using Cu(I) catalyzed azide‐alkyne click reaction and the arm‐first approach. α‐Silyl protected alkyne polystyrene (α‐silyl‐alkyne‐PS) was prepared by ATRP of styrene (St) and used as macroinitiator in a crosslinking reaction with divinyl benzene to successfully give multiarm star homopolymer with alkyne periphery. Linear azide end‐functionalized poly(ethylene glycol) (PEG‐N₃) and poly (tert‐butyl acrylate) (PtBA‐N₃) were simply clicked with the multiarm star polymer described earlier to form star block or mixed‐block copolymers in N,N‐dimethyl formamide at room temperature for 24 h. Obtained multiarm star block and mixed‐block copolymers were identified by using ¹H NMR, GPC, triple detection‐GPC, atomic force microscopy, and dynamic light scattering measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 99–108, 2010     

Preparation of amphiphilic poly(ethylene oxide)‐block‐polystyrene macrocycles via glaser coupling reaction under CuBr/pyridine system

The amphiphilic cyclic poly(ethylene oxide)‐block‐polystyrene [c‐(PEO‐b‐PS)] was synthesized by cyclization of propargyl‐telechelic poly(ethylene oxide)‐block‐polystyrene‐block‐poly(ethylene oxide) (?? PEO‐b‐PS‐b‐PEO? ?) via the Glaser coupling. The hydroxyl‐telechelic ABA triblock PEO‐b‐PS‐b‐PEO was first prepared by successive living anionic polymerization of styrene and ring‐opening polymerization of ethylene oxide, and then the hydroxyl ends were reacted with propargyl bromide to obtain linear precursors with propargyl terminals. Finally, the intramolecular cyclization was conducted in pyridine under high dilution by Glaser coupling of propargyl ends in the presence of CuBr under ambient temperature, and the c‐(PEO‐b‐PS) was directly obtained by precipitation in petroleum ether with high efficiency. The cyclic products and their corresponding linear precursor ?? PEO‐b‐PS‐b‐PEO? ? were characterized by means of GPC, ¹H NMR, and FTIR. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of a water‐soluble diblock copolymer of polysulfonic diphenyl aniline and poly(ethylene oxide)

We report the synthesis of a water‐soluble diblock copolymer composed of polysulfonic diphenyl aniline (PSDA) and poly(ethylene oxide) (PEO), which was prepared by reacting an amine‐terminated PSDA and tosylate PEO (PEO‐Tos). First, a HCl‐mediated polymerization of sulfonic diphenyl aniline monomer with the formation of HCl‐doped PSDA was carried out. After its neutralization and reduction, a secondary amine‐functionalized PSDA was obtained. Second, PEO‐Tos was synthesized via the tosylation of the monohydroxyl PEO methyl ether with tosylol chloride. Diblock copolymers with various PEO segment lengths (PSDA‐b‐PEO‐350 and PSDA‐b‐PEO‐2000) were obtained with PEO‐350 [number‐average molecular weight (M_n) = 350] and PEO‐2000 (M_n = 2000). The prepolymers and diblock copolymers were characterized by Fourier transform infrared spectroscopy, NMR, mass spectrometry, and ultraviolet–visible light. They had relatively low conductivities, ranging from 10^?6 to 10^?3 S/cm, because of the withdrawing effect of the sulfonic group as well as the steric effects of the bulky aromatic substitutuents at the N sites of the polyaniline backbone and of the PEO block. These polymers were self‐doped, and an intermolecular self‐doping was suggested. The external doping was, however, more effective. The self‐doping induced aggregation in water among the PSDA backbones, which was also stimulated by the presence of hydrophilic PEO blocks. Furthermore, the electrical conductivities of the diblock copolymers were strongly temperature‐dependent. PSDA‐b‐PEO‐2000 exhibited about one order of magnitude increase in conductivity upon heating from 32 to 57 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2179–2191, 2004     

Effects of lithium salt and poly(4‐vinyl phenol) on crystalline and amorphous phases in poly(ethylene oxide)

Effects of a strong‐interacting amorphous polymer, poly(4‐vinyl phenol) (PVPh), and an alkali metal salt, lithium perchlorate (LiClO₄), on the amorphous and crystalline domains in poly(ethylene oxide) (PEO) were probed by differential scanning calorimetry (DSC), optical microscopy (OM), and Fourier transform infrared spectroscopy (FTIR). Addition of lithium perchlorate (LiClO₄, up to 10% of the total mass) led to enhanced T_g's, but did not disturb the miscibility state in the amorphous phase of PEO/PVPh blends, where the salt in the form of lithium cation and ClO anion was well dispersed in the matrix. Competitive interactions between PEO, PVPh, and Li⁺ and ClO ions were evidenced by the elevation of glass transition temperatures and shifting of IR peaks observed for LiClO₄‐doped PEO/PVPh blend system. However, the doping distinctly influenced the crystalline domains of LiClO₄‐doped PEO or LiClO₄‐doped PEO/PVPh blend system. LiClO₄ doping in PEO exerted significant retardation on PEO crystal growth. The growth rates for LiClO₄‐doped PEO were order‐of‐magnitude slower than those for the salt‐free neat PEO. Dramatic changes in spherulitic patterns were also seen, in that feather‐like dendritic spherulites are resulted, indicating strong interactions. Introduction of both miscible amorphous PVPh polymer and LiClO₄ salt in PEO can potentially be a new approach of designing PEO as matrix materials for electrolytes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3357–3368, 2006     

An NMR investigation of the interaction of polyethylene oxide with water‐soluble poly(vinyl phenol‐co‐potassium styrene sulfonate)

The water‐soluble complex of polyethylene oxide (PEO) with poly (vinyl phenol‐co‐potassium styrene sulfonate) (PVPh‐co‐KSS) was studied by liquid‐state NMR. PEO showed two peaks in the ¹H spectra, which corresponded to the free and complexed PEO. The ratio of the free PEO/complexed PEO was decreased with the increase in the mixing ratio of PVPh‐co‐KSS/PEO. Some of the complex formation disappeared when the pH was raised from 6.4 to 12.0. It had been thought that at high pH, the phenolic groups dissociate and thus cannot form hydrogen bonds. The fact that NMR indicates some interaction at pH 12.0 implies there are some other interactions, such as hydrophobic interactions between the aromatic rings and the polyether methylene groups, contributing to PEO and PVPh‐co‐KSS complex formation. Nuclear Overhauser effect (NOE) cross peaks were observed between PEO and the aromatic protons of PVPh‐co‐KSS in nuclear Overhauser effect spectra (NOESY) suggesting that the distance between PEO and the aromatic protons of PVPh‐co‐KSS was less than 5 Å. The exchange between the complexed PEO and the free PEO was slow on the NMR time scale. The ratio of the integral of the complexed PEO to the free PEO increased with temperature, indicating that the number of PEO segments interacting with the aromatic ring increases with temperature. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1276–1284, 2000     

Synthesis of telechelics and block copolymers via “living” radical polymerization

Hydroxy‐telechelic poly(methyl methacrylate)s of molecular weights below 5000 were obtained by atom transfer radical polymerization (ATRP) of methyl methacrylate followed by end‐capping with allyl alcohol via atom transfer radical addition (ATRA). As initiators for the ATRP, monofunctional initiators with an additional hydroxy group in the molecule or bifunctional initiators were employed. The successful synthesis of the hydroxy‐telechelic PMMA was proved by determination of their molecular weight using MALDI‐TOF‐MS. The efficiency of the end‐capping reaction was determined by ¹H NMR spectroscopy using the allyl N‐(4‐tolyl)carbamate as end‐capping agent. Block copolymers comprising a poly(ethylene oxide) (PEO) block and a poly(methyl methacrylate) (PMMA) block were prepared by ATRP using a macroinitiator on the PEO basis. The dormant species of the macroinitiator consists of the phenyl chloroacetate moiety which shows a high rate of initiation. The successful synthesis of the poly(ethylene oxide)‐block‐poly(methyl methacrylate) was proved by ¹H NMR spectroscopy; the ratios of EO/MMA repeating units in the feed and the copolymer were nearly equal.     

Structural and transport characteristics of polyethylene oxide/phenolic resin blend solid polymer electrolytes

Details on the structure and transport characteristics of the solid polymer electrolyte polyethylene oxide (PEO)/lithium salt (LiClO₄) modified by novolac phenolic resin are presented here. From IR spectra it could be concluded that complex formation occurred through multiple interactions between the ether oxygen of PEO–lithium, phenolic lithium, and the phenolic ether oxygen of PEO. The free hydroxyl band in phenolic reflected that phenolic closely interacted with both the PEO polymer and ionic salt. With increasing salt content in PEO, the vibration band corresponding to the ClO anion (～623 cm^?1) displayed growth of a shoulder at ～635 cm^?1, suggesting the formation of Li⁺…ClO₄^? ion pairing. However, in the presence of phenolic, ion‐pairing formation was effectively suppressed, which suggested that the phenolic moiety facilitated a greater degree of LiClO₄ salt dissociation. Activation energy analysis revealed two conducting pathways: one through the amorphous PEO and the other through the PEO/phenolic amorphous matrix. The high ion conductivity originated from effective salt dissociation and the establishment of a new conduction network formed by PEO and phenolic. Furthermore, the structural modification also extended the thermal stability and mechanical strength of the solid polymer electrolyte composite. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3866–3875, 2004     

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