Novel block ionomers II. Synthesis and characterization of polyisobutylene‐based block cationomers

Various novel block cationomers consisting of polyisobutylene (PIB) and poly[2‐(dimethylamino)ethyl methacrylate] (PDMAEMA) segments were synthesized and characterized. The specific targets were various molecular weight diblocks (PIB‐b‐PDMAEMA⁺) and triblocks (PDMAEMA⁺‐b‐PIB‐b‐PDMAEMA⁺), with the PIB blocks in the DP_n = 50–200 range (number‐average molecular weight = 3,000–9000 g/mol) connected to blocks of PDMAEMA⁺ cations in the DP_n = 5–20 range (where DP is the number‐average degree of polymerization). The overall synthetic strategy for the preparation of these block cationomers had four steps: (1) synthesis by living cationic polymerization of mono‐ and diallyltelechelic polyisobutylenes, (2) end‐group transformation to obtain PIBs fitted with termini capable of mediating the atom transfer radical polymerization (ATRP) of DMAEMA, (3) ATRP of DMAEMA, and (4) quaternization of PDMAEMA to PDMAEMA ⁺I^? by CH₃I. Scheme 1 shows the microarchitecture and outlines the synthesis route. Kinetic and model experiments provided guidance for developing convenient synthesis methods. The microarchitecture of PIB–PDMAEMA di‐ and triblocks and the corresponding block cationomers were confirmed by ¹H NMR and FTIR spectroscopy and solubility studies. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3679–3691, 2002     

Star–block polymers of multiple polystyrene-b-polyisobutylene arms radiating from a polydivinylbenzene core

The synthesis together with mechanical property and rheological characterization of novel star–block copolymers comprising multiple polystyrene (PSt)-b-polyisobutylene (PIB) arms emanating from polydivinylbenzene (PDVB) cores are described. The synthesis strategy involved the preparation of PSt-b-PIB-Cl^t (i.e., diblocks fitted with a tert-chlorine terminus at the PIB end) by sequential living block polymerization of St and IB, ionizing the -Cl^t terminus by TiCl₄ at room temperature, and linking the PSt-b-PIB^⊕ prearms by DVB. Molecular characterization was effected mainly by triple detector GPC including refractive index (RI)-, UV-, and laser light scattering (LLS)-GPC traces. Evidence for intra- and intermolecular reactions between individual star–blocks is presented and a comprehensive mechanism to the final product is proposed. The stress–strain behavior of star–blocks has been studied and is compared with those of linear triblocks (i.e., two-arm stars) of similar arm molecular weights and composition in the 25–70°C range. The mechanical properties of star–blocks are invariably superior to those of the triblocks over the entire temperature range. The rheological behavior of star–blocks and linear triblocks has been compared in terms of dynamic viscosity at various frequencies. Star–blocks exhibit significantly lower melt viscosities than their linear counterparts, which signals improved processing behavior. We have also compared select rheological properties of the commercially available PSt-b-(hydrogenated-1,4-polybutadiene)-b-PSt thermoplastic elastomer (Kraton G 1650) with those of PIB-based linear triblocks and multiarm star–blocks of similar glassy/rubbery compositions. The melt viscosities of PIB-based triblocks and star–blocks were significantly lower than that of Kraton G over the entire frequency range investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2235–2243, 1999     

Quasiliving Carbocationic Polymerization. XVII. Synthesis Of Poly (Styrene-β-Isobutylene-β-Styrene)

Poly(styrene-b-isobutylene-b-styrene) has been synthesized by sequential carbocationic polymerization under quasiliving conditions at -90°C. The quasiliving synthesis was effected by first continuously and slowly condensing gaseous isobutylene (IB) to a bifunctional initiating system (p-dicumyl chloride/TiCl₄) dissolved in a hexane-methylene chloride (60:40 v/v) mixture. After the quasiliving polyisobutylene (PIB) sequence had reached a desired molecular weight, styrene (St) was continuously and slowly added to produce the polystyrene (PSt) sequence. The products consisted of the target triblock. However, due to initiation by impurities and possibly to chain transfer to both IB and St, it also contained diblocks and small amounts of homopolymers. While the latter could be removed by selective fractionation, the triblocks and diblocks could not be separated. The mechanism of quasiliving polymerization leading to PIB/PSt blocks is discussed.     

Study of molecular motion of block copolymers in solution by high-resolution proton magnetic resonance

Molecular motions of hydrophobic–hydrophilic water-soluble block copolymers in solution were investigated by high-resolution proton magnetic resonance (NMR). Samples studied include block copolymers of polystyrene–poly(ethylene oxide), polybutadiene–poly(ethylene oxide), and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide). NMR measurements were carried out varying molecular weight, temperature, and solvent composition. For AB copolymers of polystyrene and poly(ethylene oxide), two peaks caused by the phenyl protons of low-molecular-weight (M?_n = 3,300) copolymer were clearly resolved in D₂O at 100°C, but the phenyl proton peaks of high-molecular-weight (M?_n = 13,500 and 36,000) copolymers were too broad to observe in the same solvent, even at 100°C. It is concluded that polystyrene blocks are more mobile in low-molecular-weight copolymer in water than in high-molecular-weight copolymer in the same solvent because the molecular weight of the polystyrene block of the low-molecular-weight copolymer is itself small. In the mixed solvent D₂O and deuterated tetrahydrofuran (THF-d₈), two peaks caused by the phenyl protons of the high-molecular-weight (M?_n = 36,000) copolymer were clearly resolved at 67°C. It is thought that the molecular motions of the polystyrene blocks are activated by the interaction between these blocks and THF in the mixed solvent.     

Novel thermoplastic elastomers. II. Properties of star‐block copolymers of PSt‐b‐PIB arms emanating from cyclosiloxane cores

Select mechanical, thermal, and rheological properties of star‐blocks consisting of 5–21 polystyrene‐b‐polyisobutylene (PSt‐b‐PIB) arms radiating from cyclosiloxane cores are described. The tensile properties of products containing 23–41 wt % of PSt are substantially higher (9.6–23.8 MPa) than those of linear triblocks of comparable arm molecular weights and compositions over the 25–85°C temperature range. The mechanical properties of star‐blocks seem to be much less sensitive to diblock contamination than linear triblock thermoplastic elastomers of similar hard/soft segment composition. The tensile strength of star‐blocks increases by increasing the number of arms (N_w,arm) and reaches a plateau in the N_w,arm = 5–10 range. Star‐blocks exhibit higher strengths with lower PSt segmental M_n than linear triblocks. Solvent cast triblock copolymers exhibit higher tensile strengths than compression molded products; however, star‐blocks show no significant property differences between cast and molded samples. The dynamic melt viscosities of the star‐blocks are substantially lower than those of linear triblocks with comparable hard/soft segment compositions, which is consistent with the star's unique microarchitecture and should lead to improved overall processibility. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 815–824, 1999     

Poly(N-isopropylacrylamide-co-N-t-butylacrylamide)-block-poly(ethylene glycol)-block-poly(N-isopropylacrylamide-co-N-t-butylacrylamide) triblock copolymers: synthesis and thermogelation properties of aqueous solutions

Novel triblock copolymers with PEG middle blocks of 1–10 kDa and poly(N-isopropylacrylamide-co-t-butylacrylamide) statistical copolymer side arms with DP_n?≈?88 and different compositions, were synthesized by SET-LRP. The thermogelation properties of their aqueous solutions depended on both hydrophobic monomer content of the side blocks and molecular weight (MW) of the poly(ethylene glycol) (PEG) middle block, as proven by dynamic rheometry, DSC, and tube inversion method measurements. At constant PEG chain length, increasing TBAM proportions led to a gelation process occurring at progressively lower temperatures, as well as to a lower stability of the forming hydrogels in the case of shorter-PEG-chain block copolymers. By employing longer PEG blocks (M_PEG ≥6,000 Da), stable hydrogels with the gelation temperature below 37 °C could be obtained. For a constant composition of the copolyacrylamide blocks, the dependence of the phase transition temperature (T_ph) on M_PEG displayed a different shape at different polymer solution concentrations, because of the stronger variation of T_ph with polymer concentration as M_PEG increased. Also, the viscoelastic properties of the hydrogels resulting from 20 wt.% polymer aqueous solutions at 37 °C were stronger affected by the MW of the PEG middle block than by the hydrophobic character of the thermosensitive side blocks.     

The synthesis and self‐assembly of ABA amphiphilic block copolymers containing styrene and oligo(ethylene glycol) methyl ether methacrylate in dilute aqueous solutions: Elevated cloud point temperatures for thermoresponsive micelles

A series of ABA amphiphilic triblock copolymers possessing polystyrene (PS) central hydrophobic blocks, one group with “short” PS blocks (DP = 54–86) and one with “long” PS blocks (DP = 183–204) were synthesized by atom transfer radical polymerization. The outer hydrophilic blocks were various lengths of poly(oligoethylene glycol methyl ether) methacrylate, a comb‐like polymer. The critical aggregation concentrations were recorded for certain block copolymer samples and were found to be in the range circa 10⁻⁹ mol L⁻¹ for short PS blocks and circa 10⁻¹² mol L⁻¹ for long PS blocks. Dilute aqueous solutions were analyzed by transmission electron microscopy (TEM) and demonstrated that the short PS block copolymers formed spherical micelles and the long PS block copolymers formed predominantly spherical micelles with smaller proportions of cylindrical and Y‐branched cylindrical micelles. Dynamic light scattering analysis results agreed with the TEM observations demonstrating variations in micelle size with PS and POEGMA chain length: the hydrodynamic diameters (D_H) of the shorter PS block copolymer micelles increased with increasing POEGMA block lengths while maintaining similar PS micellar core diameters (D_C); in contrast the values of D_H and D_C for the longer PS block copolymer micelles decreased. Surface‐pressure isotherms were recorded for two of the samples and these indicated close packing of a short PS block copolymer at the air–water interface. The aggregate solutions were demonstrated to be stable over a 38‐day period with no change in aggregate size or noticeable precipitation. The cloud point temperatures of certain block copolymer aggregate solutions were measured and found to be in the range 76–93 °C; significantly these were ∼11 °C higher in temperature than those of POEGMA homopolymer samples with similar chain lengths. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7739–7756, 2008     

Polyisobutylene-containing block polymers by sequential monomer addition. II. Polystyrene–polyisobutylene–polystyrene triblock polymers: Synthesis,characterization, and physical properties

New linear and three-arm star thermoplastic elastomers (TPEs) comprising a rubbery polysobutylene (PIB) midblock flanked by glass polystyrene (PSt) blocks have been synthesized by living carbocationic polymerization in the presence of select additives by sequential monomer addition. First, isobutylene (IB) was polymerized by bi- and trifunctional tert-ether (dicumyl- and tricumyl methoxy) initiators in conjunction with TiCl₄ conintiator in CH₃Cl/methylcyclohexane (MeCHx) (40/60 v/v) solvent mixtures at ?80°C. After the living, narrow molecular weight, distribution PIB (M?_w/M?_n = 1.1-1.2) has reached the desired molecular weight, styrene (St) together with an electron pair donor (ED) and a proton trap (di-tert-butylpyridine, DtBP) were added to block PSt from the living chain ends. Uncontrolled initiation by protic impurities that produces PSt contamination is prevented by the use of DtBP. PSt-PIB-PSt blocks obtained in the absence of additives are contaminated by homopolymer and /or diblocks due to inefficient blocking and initiation by protic impurities, and exhibit poor physical properties. In contrast in the presence of the strong ED N,N-dimethylacetamide (DMA) and DtBP the blocking of St from living PIB chain occurs efficiently and block copolymers exhibiting good mechanical properties can be prepared. Virgin TPEs can be repeatedly compression molded without deterioration of physical properties. The products exhibit a low and a high temperature T_g characteristic of phase separated PIB and PSt domains. Transmission electron microscopy of linear triblocks containing ～ 34 wt % PSt also indicates microphase separation and suggests PSt rods dispersed in a PIB matrix.     

Polyisobutylene-Based Thermoplastic Elastomers. I. Synthesis and Characterization of Polystyrene-Polyisobutylene-Polystyrene Triblock Copolymers

Abstract

Polystyrene-polyisobutylene-polystyrene triblock copolymer thermoplastic elastomers have been synthesized by living carbocationic sequential copolymerization using the tert-butyl dicumyl chloride/TiCl₄/methylcyclohexane:methyl chloride (60:40 v:v)/ ?80°C system in the presence of the proton trap 2,6-di-tert-butylpyridine. Structure-property relationships have been examined by varying the M_n of the PIB middle block (39,000 to 156,000) and that of the PSt end-segment (1,000 to 19,000). The tensile strength is controlled by the molecular weight of the PSt segment and independent of the PIB middle block length in the studied range. Phase separation starts when the M_n of the PSt segment reaches ～ 5,000, and it is complete when the M_n reaches ～ 15,000. These triblocks exhibited 23-25 MPa tensile strength, similar to that of styrenic thermoplastic elastomers obtained by anionic polymerization.     

Grafting by in situ coupling of epoxy groups of a living copolymer with an anionic living polymer

A tetrahydrofuran (THF) solution of the living random copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) was prepared by the living anionic copolymerization of the two monomers, using 1,1‐diphenylhexyllithium (DPHLi) as initiator, in the presence of LiCl ([LiCl]/[DPHLi]₀ = 3), at −50°C. The copolymer thus obtained has a controlled composition and molecular weight and a narrow molecular weight distribution. By introduction of an anionic living polystyrene (poly(St)) or anionic living polyisoprene (poly(Is)) solution into the above system at −30°C, a coupling reaction took place and a graft copolymer with a polar backbone and nonpolar side chains was produced. The solvent used in the preparation of the living poly(St) or poly(Is) affects the coupling reaction. When benzene was the solvent, a graft copolymer of high purity, controlled graft number and molecular weight, and narrow molecular weight distribution (M_w/M_n = 1.11–1.21) was obtained. In the coupling reaction, the living poly(St) reacted only with the epoxy groups and not with the carbonyls of the backbone polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 105–112, 1999     

Synthesis and radical polymerization of styrene derivative bearing kojic acid moieties

A styrene derivative ( 1 ) bearing kojic acid moieties was prepared by the base-catalyzed reaction of p-formylstyrene with kojic acid. Hydroxyl groups in 1 were subjected to acetylation. Although 1 did not undergo radical polymerization, the acetylated styrene derivative ( 2 ) showed good radical homo- and copolymerizability. For instance, a polymer having the number average molecular weight (M_n) of 60,000 was obtained in almost quantitative yield (97%) by the polymerization of 2 in chloroform (1.5 M) at 60°C for 36 h using α,α′-azobis(isobutyronitrile) (AIBN, 5 mol %) as an initiator. Under similar conditions, copolymers of 2 with styrene were also obtained in high yield. By partial deacetylation of the copolymer with a triethylamine catalyst, a copolymer containing α-hydroxyketone structures originated from kojic acid moieties was successfully regenerated. The deacetylated copolymer can be crosslinked by complexation with metal salts such as Al³⁺. © 1996 John Wiley & Sons, Inc.     

Crystallization of tethered polyethylene in confined geometries

Ordered poly(ethylene)‐poly(vinylcyclohexane) (PE‐PVCH) block copolymers are employed to study the crystallization of tethered PE in confined geometries. The high T_g of the PVCH component of these materials forces PE chains to crystallize in well‐defined geometries dictated by the mesophase structure of the block copolymer. Effects of chain tethering on crystallization are examined through comparison of singly‐tethered PE chains in PE‐PVCH (EV) diblocks and doubly‐tethered PE in PVCH‐PE‐PVCH (VEV) triblocks. Crystallinity is independent of the block copolymer mesophase structure in both the EV and VEV systems, although crystallinity in VEV depends on the molecular weight of the PE block of the copolymer. Melting temperature data indicate that spatial confinement reduces crystallite size in EV and VEV, and that the double tethering of PE chains in VEV reduces crystallite size further through topological constraints. Crystal nucleation and growth depend strongly on the type of microstructure in both EV and VEV block copolymers. Differences in the overall rate of crystallization are correlated with the dimensional continuity of the PE microdomains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37:2053–2068, 1999     

Amphiphilic graft copolymers with poly(oxyethylene) side chains: Synthesis via phthalimidoacrylate prepolymers

Amphiphilic graft copolymers of definite composition were obtained by grafting of amino-functionalized poly(oxyethylene) monoether (MPEO–NH₂) of M?_n = 750, 2000, and 5000 onto phthalimidoacrylate (PIA) homopolymer or its copolymer with styrene (St). The radical co-polymerization of PIA and phthalimidomethacrylate (PIMA) with St was studied in dimeth-ylformamide (DMF) at 60°C. The copolymer composition curves and the monomer reactivity ratios showed a high tendency of PIA to alternating copolymerization with St (r₁r₂ = 0.006). Hydrogen bonding between the functional groups leads to significant spectral modifications. The micellization of the graft copolymers was studied by GPC in aqueous-methanolic eluent. The aggregation behavior of the graft copolymers depended on their composition and chromato-graphic separation lead to the copolymers fractionation. © 1995 John Wiley & Sons, Inc.     

Synthesis and Structure/Property Relationships of Regioselective 2‐O‐, 3‐O‐ and 6‐O‐Ethyl Celluloses

Regioselectively ethylated celluloses, 2‐O‐ ( 1 ), 3‐O‐ ( 2 ), and 6‐O‐ethyl‐ ( 3 ) celluloses were synthesized via ring‐opening polymerization of glucopyranose orthopivalate derivatives. The number‐average degrees of polymerization (DP_ns) of compounds 1 and 2 were calculated to be 10.6 and 49.4, respectively. Three kinds of compound 3 with different DP_ns were prepared: DP_ns = 12.9 ( 3‐1 ), 60.3 ( 3‐2 ), and 36.1 ( 3‐3 ). The 2‐O‐, 3‐O‐, and 6‐O‐ethylcelluloses were soluble in water, confirmed by NMR analysis. Furthermore, the 3‐O‐ ( 2 ), and 6‐O‐ethyl‐ ( 3‐2 ) celluloses showed thermo‐responsive aggregation behavior and had a lower critical solution temperature (LCST) at about 40 °C and 70 °C, respectively, based on the results from turbidity tests and DSC measurements. The 6‐O‐ethyl‐cellulose ( 3‐3 ) with DP_n = 36.1 and DP_w = 54.6 showed gelation behavior over approx 70 °C, whereas the 6‐O‐ethyl‐celluloses 3‐1 and 3‐2 with lower and higher molecular weight, such as DP_ns 12.9 and 60.3, did not show gelation behavior at this temperature. It was revealed that the position of ethyl group affected the phase transition temperature. According to our experiments, the 3‐O‐ethyl and 6‐O‐ethyl groups along the cellulose chains caused the thermo‐responsive property of their aqueous solutions. The appropriate DP of the regioselective 6‐O‐ethyl‐cellulose existed for gelation of the aqueous solution.

     

A successive route to amphiphilic graft copolymers with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic polystyrene side chains

A successive method for preparing novel amphiphilic graft copolymers with a hydrophilic backbone and hydrophobic side chains was developed. An anionic copolymerization of two bifunctional monomers, namely, allyl methacrylate (AMA) and a small amount of glycidyl methacrylate (GMA), was carried out in tetrahydrofuran (THF) with 1,1‐diphenylhexyllithium (DPHL) as the initiator in the presence of LiCl ([LiCl]/[DPHL]₀ = 2), at −50 °C. The copolymer poly(AMA‐co‐GMA) thus obtained possessed a controlled molecular weight and a narrow molecular weight distribution (M_w /M_n = 1.08–1.17). Without termination and polymer separation, a coupling reaction between the epoxy groups of this copolymer and anionic living polystyrene [poly(St)] at −40 °C generated a graft copolymer with a poly(AMA‐co‐GMA) backbone and poly(St) side chains. This graft copolymer was free of its precursors, and its molecular weight as well as its composition could be well controlled. To the completed coupling reaction solution, a THF solution of 9‐borabicyclo[3.3.1]nonane was added, and this was followed by the addition of sodium hydroxide and hydrogen peroxide. This hydroboration changed the AMA units of the backbone to 3‐hydroxypropyl methacrylate, and an amphiphilic graft copolymer with a hydrophilic poly(3‐hydroxypropyl methacrylate) backbone and hydrophobic poly(St) side chains was obtained. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1195–1202, 2000     

Copolymerization of carbon monoxide with 1,3-cyclopentadiene by palladium complexes

Copolymerization of carbon monoxide with 1,3-cyclopentadiene (CPD) by palladium complexes, [Pd(CH₃CN)_4?n (PPh₃)n] (BF₄)₂, n = 1–3 (especially n = 1), was studied at 60°C. Results of elementary analysis, infrared spectra, and NMR spectra showed that copolymers containing ketone and ring structures were produced. Phosphorus compounds such as PPh₃ were found to be more effective stabilizing ligands for the catalytic activity compared to arsenic or nitric ligands. A higher activity of the catalyst for the copolymerization of CPD with carbon monoxide was observed in noncoordinating solvents such as CHCl₃ even at a pressure as low as 300 psi. The amount of 1,2 structure for the CPD-CO copolymer increased as the polarity of solvent increased. The copolymer was confirmed to be partially crystalline by the x-ray diffraction. TGA shows that weight loss of copolymer starts at 120°C and the maximum peak of decomposition occurs at 469°C. © 1993 John Wiley & Sons, Inc.     

Co60 γ-radiation-induced copolymerization of ethylene and carbon monoxide

The γ-radiation-induced free-radical copolymerization of ethylene and CO has been investigated over a wide range of pressure, initial gas composition, radiation intensity, and temperature. At 20°C., concentrations of CO up to 1% retard the polymerization of ethylene. Above this concentration the rate reaches a maximum between 27.5 and 39.2% CO and then decreases. The copolymer composition increases only from 40 to 50% CO when the gas mixture is varied from 5 to 90% CO. A relatively constant reactivity ratio is obtained at 20°C., indicating that CO adds 23.6 times as fast as an ethylene monomer to an ethylene free-radical chain end. For a 50% CO gas mixture, the above value of 23.6 and the copolymerization rate decrease with increasing temperature to 200°C. The kinetic data indicate a temperature-dependent depropagation reaction. Infrared examination of copolymers indicates a polyketone structure containing ? CH₂? CH₂? and ? CO? units. The crystalline melting point increases rapidly from 111 to 242°C., as the CO concentration in the copolymer increases from 27 to 50%. Molecular weight of copolymer formed at 20°C. increased with increasing CO, indicating M?_n values >20,000. Increasing reaction temperature results in decreasing molecular weight. Onset of decomposition for a 50% CO copolymer was measured at ≈250°C.     

Determination of the cumulative degree of polymerization for the dead‐end polymerization of styrene

This article explores the use of a new relation correcting theoretical (DPn ) with experimental values obtained in the dead‐end polymerization of styrene with azocompound. The syntheses were realized for several starting initiator‐to‐monomer ratios (C₀'s); values comprised between 10 and 0.1%, and the experimental (DPn ) were obtained by size exclusion chromatography. Concerning the theoretical (DPn ), a new relation is proposed considering the loss of initiating radicals [I · ] used in primary termination and both stationary states of I · and M · (macromolecular radicals) introduced as Bamford. Finally, (DPn )_cum, previously defined by us, is introduced to consider the monomer conversion during oligomerization. Our relation fit very well in a large range of C₀'s, contrary to the application of the usual Mayo rule, and a discussion of validity is proposed. Our model also allows the prediction of (DPn )_cum in a large range of telechelic oligomers from 10 to 150. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 236–247, 2003     

THERMAL BEHAVIOR AND IONIC CONDUCTIVITY OF POLY[LITHIUM-N(4-SULFO-PHENYL) MALEIMIDE -CO-METHOXY OLIGO(OXYETHYLENE) METHACRYLATE]

Poly[lithium-N(4-sulfophenyl) maleimide -co- methoxy oligo-(oxyethylene) methacrylates] [P(LiSMOE_n)s] with three different oligoether side chains and different salt concentrations were synthesized. The copolyelectrolytes are essentially random in structure, with blocks of methoxy oligo(oxyethylene) meth-acrylate (MOE_nM) recurring sporadically in between the salt units of N(4-sulfophenyl) maleimide. They all show two glass transitions in the temperature range of ?100 to 100°C. The first one below ?30°C is assigned to the oligo(oxyethylene) side chain (T _g1), while the second one located between 20 and 50°C is attributed to the main chain of the polymer host (T _g2). The maximum ionic conductivity of the copolymer electrolytes, 1.6 × 10^?7 S cm^?1 at 25°C, occurs at lithium salt concentration [Li⁺]/[EO] = 2.2 mol%. The ionic conductive behavior of the copolyelectrolytes follows the Vogel-Tammann-Fulcher (VTF) equation. Moreover, a special VTF behavior exists in the copolymers with shorter oligoether side chain and higher salt concentration. Sweep voltammetric results indicate that these copolyelectrolytes have a good electrochemical stability window.     

Controlling grafting density and side chain length in poly(n‐butyl acrylate) by ATRP copolymerization of macromonomers

Atom transfer radical polymerization (ATRP) was used for the preparation and subsequent copolymerization of two acryloyl‐terminated poly(n‐butyl acrylate) macromonomers with different degrees of polymerization (DP_nBA = 25 and 42). Homopolymerization of the higher molecular weight macromonomer ( MM1 ; PnBA₄₂‐A, M_n = 5600, DP_MM = 42, M_w/M_n = 1.18) resulted in preparation of a densely grafted polymer with a narrow molecular weight distribution (M_w/M_n = 1.14), but with the limited degree of polymerization DP = 12. The ultimate degree of homopolymerization for the lower molecular weight macromonomer ( MM2 ; PnBA₂₅‐A, M_n = 3400, DP_MM = 25, M_w/M_n = 1.20) was higher, and DP increased from 12 to 22. The limited DP could be because of progressively increasing steric congestion for macromonomers in approaching the growing chain ends of densely grafted polymers. When MMs were copolymerized with nBA, the reactivity of MM was nearly the same as that of nBA monomer irrespective of the differences in the degree of polymerization of the MMs and the initial molar ratio of nBA to MM. Well‐defined graft polymers with different lengths of backbone and side chains, and different graft density were successfully prepared by “grafting through” ATRP. Tadpole‐shaped and dumbbell‐shaped graft polymers were also synthesized by ATRP. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5454–5467, 2006