Counter‐Anion Effect on the Properties of Anion‐Conducting Polymer Electrolyte Membranes Prepared by Radiation‐Induced Graft Polymerization

Graft‐type anion‐conducting polymer electrolyte membranes (AEMs) are prepared by the radiation‐induced graft polymerization of chloromethylstyrene into poly(ethylene‐co‐tetrafluoroethylene) (ETFE) films and subsequent quaternization with trimethylamine. AEMs in the hydroxide form (AEM‐OH) are prepared by immersing the chloride form (AEM‐Cl) in 1 M potassium hydroxide (KOH) solution, followed by KOH and washing with nitrogen‐saturated water to prevent bicarbonate formation (AEM‐HCO₃). The AEM‐OH shows conductivity and water uptake four and two times higher than AEM‐Cl and ‐HCO₃ and is thermally and chemically less stable, resulting in the tendency to absorb water and to convert to the bicarbonate form.

     

SAXS Investigation on Morphological Change in Lamellar Structures During Propagation Steps of Graft‐Type Polymer Electrolyte Membranes for Fuel Cell Applications

The changes of the lamellar periods (L_1D), thickness of lamellar crystals (L_c), and amorphous layers (L_a) within the stacked lamellae of poly(styrenesulfonic acid)‐grafted poly(ethylene‐co‐tetrafluoroethylene) polymer electrolyte membranes (ETFE‐PEMs), induced by the preparation and water‐absorbing steps are investigated using the small‐angle X‐ray scattering method. The L_1D values of all the samples quickly increase at a grafting degree (GD) range of less than 19% and then level off. The solvent‐induced recrystallization is observed at the early stage of grafting (GD < 10%) and at successive sulfonation and hydration steps. The L_1D, L_a, and L_c of dry and hydrated PEMs show similar values at higher GD ranges (>34%), leading to the conclusion that most water molecules in the PEMs with higher GDs exist at the outside of the lamellar stacks. Accordingly, for the PEMs with low GD (<19%), all the hydrophilic graft‐polymers (ion‐channels) locate in the lamellar stacks and are strongly restricted by lamellar crystalline layers, which suppress the swelling of the PEMs. The unique lamellar structures of ETFE‐PEMs characterized by L_a and L_c are well connected with the high conductance and mechanical properties of the membranes, and are suitable for fuel cell applications.     

Effects of Polymer Concentration on Structure and Properties of Zwitterionic Nanocomposite Gels

Zwitterionic nanocomposite gels (Zw‐NC gels) composed of a zwitterionic sulfobetaine copolymer and inorganic clay (hectorite) are synthesized through the in situ free‐radical copolymerization of N,N‐dimethyl(acrylamidopropyl)ammonium propanesulfonate (90 mol%) and N,N‐dimethylacrylamide (10 mol%) with exfoliated clay platelets in an aqueous medium. The effects of polymer concentration (C_p) on the dynamic viscoelasticity, tensile mechanical properties, transparency, and the thermosensitivity with the upper critical solution temperature (UCST) of the Zw‐NC gels are investigated in the range C_p = 26–260 g L^?1 and are compared with those of chemically cross‐linked zwitterionic gels. All the mechanical and thermosensitive properties strongly change depending on the type of network and C_p. The C_p‐induced changes in the polymer‐clay structure of the Zw‐NC gel are discussed based on the mechanical, optical, and thermosensitive properties, and on transmission electron microscopy and X‐ray diffraction measurements.

     

Violet Emission of ALD‐Grown ZnO Nanostructures on Confined Polymer Films: Defect Origins and Emission Control via Interface Engineering Based on Confinement of the Bottom Polymer Template

ZnO thin films on polymer templates (polystyrene, PST) show strong influence of the interface via degree of confinement of the bottom polymer template in introducing the controlled defect levels in the ZnO nanostructures and consequently yield significant variation at room temperature photoluminescence (PL). The thickness of the polymer thin film in terms of its radius of gyration (R _g) defines the degree of confinement of PST. Simultaneous growth of ZnO thin films by atomic layer deposition (ALD) with 150 cycles at 35 °C on spin‐coated polystyrene (PS) films of different thicknesses forms sets of ZnO/PST hybrid systems. The ZnO thin film exhibits a distinct/unusual violet emission (2.95 eV) along with the common near‐band‐edge and green emissions, when it grows on 6.5R _g PST. Such defect‐induced emissions disappear with increasing degree of confinement of the bottom PST from 6.5R _g to 1.5R _g, and sharper UV peak dominates the PL spectra along with a prominent redshift in near‐band‐edge. Furthermore, with increasing film thickness of the bottom PST template from 1.5R _g to 6.5R _g, the ALD growth rate of ZnO increases by 25%. The study offers new insights into the research on opto‐electronic applications of ZnO thin films in the emerging field of organic electronics.     

Phenothiazine Semiconducting Polymer for Light‐Emitting Diodes

Phenothiazine alternating copolymer poly{4,8‐bis(5‐dodecylthiophene‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐(10‐decylphenothiazine)} ( P1 ) is synthesized by Stille coupling polymerization. The synthesized polymer has an electrochemical bandgap of 1.61 eV and displays good photoluminescence with a quantum yield of 63.3%. The polymer is tested as a light‐emitting material in polymeric light‐emitting diodes (PLEDs) with a device structure of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/polymer/Cs₂CO₃/Al. The devices display an orange‐yellow electroluminescence (Commission Internationale de l'Eclairage (CIE) 1931 color‐space chromaticity diagram: x = 0.5355 and y = 0.4611) with a maximum brightness of 3130 cd m^?2 at an applied voltage of 10 V.     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 7. Synthesis of Well‐Defined Highly Branched Polymers and Graft Copolymers Having One Branch per Repeating Unit Using Poly(m‐halomethylstyrene)s as Backbone Polymers

Well‐defined poly(m‐chloromethylstyrene) and poly(m‐bromomethylstyrene) were prepared by the living anionic polymerization of m‐(tert‐butyldimethylsilyl)oxymethylstyrene and subsequent transformation reactions with BCl₃ and (CH₃)₃SiCl/LiBr. The reaction of poly(m‐chloromethylstyrene)s with 1,1‐diphenylethylene (DPE) end‐capped polystyryllithium proceeded very fast in the initial stage (76% of efficiency after 10 min) and reached quantitative reaction efficiency after 24 h at –40°C. The reaction of poly(m‐bromomethylstyrene) with DPE end‐capped polystyryllithium of molecular weight value of up to 68.8 kg/mol proceeded completely without steric hindrance of the polystyrene branch at –40°C for 168 h to afford a very high molecular weight branched polystyrene with one branch per repeating unit (M̄_w = 2.3 million). Well‐defined graft copolymers with the same architecture were also successfully synthesized by reacting poly(m‐halomethylstyrene)s with living anionic polymers of isoprene, 2‐vinylpyridine, and tert‐butyl methacrylate at –40°C for 168–336 h. The high compact structures of the branched polystyrenes synthesized here comparable to those of star‐branched polymers were confirmed by viscosity measurement performed in toluene at 35°C.     

Thermo‐Responsive and Emulsifying Properties of Poly(N‐vinylcaprolactam) Based Graft Copolymers

Thermo‐responsive graft copolymers have been synthesized based on a poly(N‐vinylcaprolactam) (PVCL) backbone and either hydrophilic poly(ethylene oxide) (PEO) or hydrophobic poly(tetrahydrofuran) (PTHF) side chains. The phase separation behavior of the graft polymers in water was studied by transmittance measurements and compared to that of the corresponding swollen segmented polymer networks and aqueous solutions of both polymers. The influence of the concentration and length of the grafts on the cloud point temperature (T_CP) has been demonstrated. PVCL‐g‐PTHF copolymers have been synthesized by using the macromonomer technique, i.e. the radical copolymerization of VCL with a PTHF macromonomer. A special feature of these amphiphilic graft copolymers is their ability to stabilize aqueous emulsions below the T_CP and to suddenly break them above the T_CP. PVCL‐g‐PEO copolymers were prepared by a grafting onto method. First, succinimide groups were introduced in the backbone, to which amino terminated PEO chains were grafted in the second step. This leads to di‐hydrophilic copolymers that become amphiphilic after heating their aqueous solutions above the T_CP.

     

Self‐Healing Metallo‐Supramolecular Amphiphilic Polymer Conetworks

The current challenge in self‐healing materials resides in the design of materials which exhibit improved mechanical properties and self‐healing ability. The design of phase‐separated nanostructures combining hard and soft phases represents an attractive approach to overcome this limitation. Amphiphilic polymer conetworks are nanostructured materials with robust mechanical properties, which can be tailored by tuning the polymer composition and chemical functionality. This article highlights the design of phase‐separated nanostructured polymers from metallo‐supramolecular amphiphilic polymer conetworks, and their application for self‐healing surfaces. The synthesis of poly(N‐(pyridin‐4‐yl)acrylamide)‐l‐polydimethylsiloxane polymer conetworks from the poly(pentafluorophenyl acrylate)‐l‐polydimethylsiloxane activated ester is presented. Loading of ZnCl₂ salt into the phase‐separated polymer conetwork strengthens the network by cross‐linking the poly(N‐(pyridin‐4‐yl)acrylamide) phases, while offering reversible interactions needed for self‐healing ability.     

Facile Synthesis of a Carnosine‐Pendent Cationic Polymer via Free Radical Polymerization and Application in Gene Delivery

l ‐carnosine is a bipeptide with varieties of biomedical benefits, but rarely reported as a component in structurally defined polymers due to the unavailability of isolatable monomers. In this report, a simple method to synthesize a carnosine‐derived methacrylamide in three steps is established and a neutral polymer with a narrow molecular weight distribution (M_n 7.6 kDa, Ð 1.2) and high structural regularity is prepared via free radical polymerization, and a carnosine‐pendent cationic homopolymer is finally achieved after trifluoroacetic acid‐mediated deprotection without a concern of impurities such as metals. The antioxidative activity, cytotoxicity, DNA‐binding capability, and gene delivery performance of the cationic polymer are also studied.     

The Photoelectric Properties of Polymer Acceptors Containing Oxadiazole and Thiadiazole

By the introduction of electron‐deficient five‐membered heterocycles 1,3,4‐oxadiazole (OZ) or 1,3,4‐thiadiazole (TZ) moieties, two new A₁–D–A₂–D‐type polymer acceptors containing naphthalene diimide, named PNOZ and PNTZ, are prepared and applied for all‐polymer solar cells. Both polymer acceptors possess deeply lowest unoccupied molecular orbital (LUMO) energy levels below −4.0 eV and show broad absorption spectra in the range of 300–800 nm. Compared with PNOZ, PNTZ shows broader and stronger absorption, slightly higher lying LUMO level and better microphase separation size. Employing PNTZ as the acceptor material and PTB7 as the donor material, the all‐polymer solar cells based on PTB7/PTNZ (1:1, by weight) give the best power conversion efficiency of 2.58% with a short‐circuit current density (J _sc) of 10.05 mA cm⁻², an open‐circuit voltage (V _oc) of 0.70 V, and a fill factor (FF) of 0.37 due to the formation of a well‐optimized, bicontinuous network of the donor and acceptor polymer domains.

     

Cholesterol Esterase Activity of a Molecularly Imprinted Polymer

A molecularly imprinted polymer with cholesterol esterase activity was prepared. Polymerization of N,N′‐diethyl(4‐vinylphenyl)amidine in the presence of the phosphate transition state analogue 2 followed by removal of the print molecule generated a catalytically active polymer with K_m of 3.7 mM and k_cat of 2.2·10^–4 min^–1, respectively. A relative rate enhancement of 27‐fold over the background buffer uncatalyzed reaction and of 2.4‐fold in the presence of the control polymer were observed.     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 5. Synthesis of Star Polymers by Reactions of End‐Functionalized Polystyrenes with Chloromethylphenyl Groups with Polymer Anions Consisting of Two Polymer Chains

Well‐defined five‐arm star polymers, having different arms in molecular weight or composition, were synthesized by linking reactions of end‐functionalized polystyrenes with two chloromethylphenyl (CMP) groups and polymer anions consisting of two identical or different polymer chains. The polymer anions were prepared by coupling living anionic polymers of styrene or isoprene with 1,1‐diphenylethylene (DPE)‐end‐functionalized polymers. They were then reacted in situ with the CMP‐end‐functionalized polystyrenes to afford heteroarm star polymers of the AA′₂A″₂, AA′₂B₂, and AB₂C₂ types where the A, B, and C segments were polystyrene, poly(a‐methylstyrene), and polyisoprene, respectively. ¹H NMR spectroscopy, SEC, vapor pressure osmometry (VPO), and static light scattering measurements evaluated the well‐defined architecture of these polymers.     

Solid Polymer Electrolytes, 9

Summary: A new hybrid polymer electrolyte system containing polysiloxane and polyether segments has been designed and prepared by epoxide crosslinking. The thermal behavior, structure and ionic conductivity of the hybrid materials were investigated and characterized by differential scanning calorimetry (DSC), ¹³C solid‐state NMR spectroscopy and alternating current (AC) impedance measurements. Two glass transition temperatures were observed, showing a dependence on the composition and LiClO₄/PC content. The miscibility of the polymer components in the hybrid was studied by examining the ¹H spin relaxation times in the laboratory frame (T₁(H)) and in the rotating frame (T_1ρ(H)) with various compositions. Multi‐relaxation T_1ρ(H) behavior has been observed, indicative of the presence of structural heterogeneity on the timescale of T_1ρ(H). These results are correlated and used to interpret the phenomenon of the conductivity of the lithium ion in the matrix of hybrid networks.

Schematic structure of polysiloxane/polyether networks.     

Water‐Soluble Polyaniline from γ‐Ray‐Induced N‐Acylation Graft Copolymerization with Acrylic Acid in the Emeraldine State

The effect of γ‐ray irradiation on the emeraldine (EM) base form of polyaniline was investigated. The processes of γ‐ray, UV, and thermally‐induced graft copolymerization of EM base with acrylic acid (AAc) in a number of solvents and co‐solvents were compared in an attempt to prepare a water‐soluble EM through N‐acylation. The presence of N‐acylation was investigated by thermogravimetric (TG) analysis, Fourier transform infrared (FTIR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS). In all cases, the graft concentration and the resulting surface conductivity were shown to be a function of the monomer concentration. The thermostability and weight loss behavior of the graft‐copolymerized EM included those that were characteristic of the EM base, the AAc polymer and the amide polymer. Some of the graft‐modified EM base samples exhibited good water solubility. In particular, the γ‐ray‐induced graft copolymerization of EM with AAc in N‐methyl‐2‐pyrrolidinone(NMP)/water co‐solvent readily gave rise to a water‐soluble, self‐protonated and semi‐conductive EM, which could be cast into free‐standing films from an aqueous solution.     

Cellulose Acetate‐graft‐Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer Composition

Summary: Several different series of cellulose acetate‐graft‐poly(hydroxyalkanoate)s (CA‐g‐PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L ‐lactide, (R,S)‐β‐butyrolactone, δ‐valerolactone and ε‐caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA‐g‐PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi‐empirical equations available for polymer blends or comb‐like polymers. In particular, the composition dependence of the T_gs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb‐like polymers, when CAs of acetyl DS ≈2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification.

     

Novel Biodegradable Heterografted Polymer Brushes Prepared via a Chemoenzymatic Approach

Biodegradable heterografted molecular bottle brushes were prepared in two steps starting with a linear polyglycidol as a macroinitiator. First, ca. 45% of the polyglycidol hydroxy groups were grafted with ε‐caprolactone via enzymatic catalysis. Selective end capping of the hydroxy groups at the graft ends was achieved via enzymatic esterification with vinyl acetate or vinyl acrylate. Finally, poly(L ‐lactide) grafts were attached to the remaining polyglycidol hydroxy groups by chemically catalyzed ring‐opening polymerization. The successful synthesis of the heterografted comb‐shaped brushes was confirmed by NMR and SEC analyses. Additionally, the feasibility of microsphere formulation was described.

     

The Stability of Free Radicals in Densely Crosslinked Acrylate Polymer Networks

The four types of crosslinked polymer samples based on pentaerythritol tetraacrylate (PETA) and propylene glycol‐425‐diacetoacetate (PGDAA) were prepared in two steps. At first the Michael dark addition of vinyl groups of PETA to PGDAA results in polymer network (cf. Scheme 1). The higher conversion of residual vinyl monomer and pendant double bonds built up in the Michael network was achieved by a photo‐initiated free radical polymerization in the second step of polymer network synthesis. The lifetime of trapped radicals was estimated by following the decay of radicals in the dark period of intermittent illumination directly in the resonator cavity of ESR spectrometer. The determined values of bimolecular termination rate constants k_t are of order 10^–1 to 10² kg/mol·s in dependence on composition, structure of network, and environment. It was observed that oxygen facilitates the decay of free radicals. The k_t values are of about 1 to 2 decimal orders higher than that determined in nitrogen. Moreover, as in each subsequent light–dark cycle the k_t was increased, we believe that it is a consequence of enhancement the diffusion of free radicals by assisted oxygen chain reaction with formation of hydroperoxides. The exception is the sample B with the highest final crosslinks density and conversion of monomers to network. More tightly trapped free radicals were present in polymer networks photo‐cured in nitrogen. The k_t values in all four types of networks decreased in each consecutive light–dark cycle.     

In vivo engineering of mobilized stem cell grafts with the immunomodulatory drug FTY720 for allogeneic transplantation

The immunological attributes of stem cell grafts play an important role in the outcome of allogeneic stem cell transplants. Currently, ex vivo manipulation techniques such as bulk T‐cell depletion or positive selection of CD34⁺ cells are utilized to improve the immunological attributes of grafts and minimize the potential for graft‐versus‐host disease (GvHD). Here, we demonstrate a novel graft engineering technique, which utilizes the immunomodulatory drug FTY720 for in vivo depletion of naïve T (T_N) cells from donor G‐CSF‐mobilized grafts without ex vivo manipulation. We show that treatment of donor mice with FTY720 during mobilization depletes grafts of T_N cells and prevents lethal GvHD following transplantation in a major mismatch setting. Importantly, both stem cells and NK cells are retained in the FTY720‐treated grafts. FTY720 treatment does not negatively affect the engraftment potential of stem cells as demonstrated in our congenic transplants or the functionality of NK cells. In addition, potentially useful memory T cells may be retained in the graft. These findings suggest that FTY720 may be used to optimize the immunological attributes of G‐CSF‐mobilized grafts by removing potentially deleterious T_N cells which can contribute to GvHD, and by retaining useful cells which can promote immunity in the recipient.     

Well-defined graft copolymers containing a poly(methacrylate) backbone and functional or block poly(vinyl ether) side chains

The anionic random copolymerization of methyl methacrylate (MMA) and 2-(1-acetoxyethoxy)ethyl methacrylate (AEEMA) was carried out using 1,1-diphenylhexyllithium (DPHL) as initiator, in the presence of LiCl ([LiCl]/[DPHL]₀ = 2), in tetrahydrofuran (THF), at –60°C. The resulting polymer, poly-(MMA-co-AEEMA), has a controlled molecular weight and a narrow molecular weight distribution (M_w/M_n = 1.05 ˜ 1.09). Without quenching, toluene, EtAlCl₂ and a functional monomer [2-acetoxyethyl vinyl ether (AcVE), 2-chloroethyl vinyl ether (ClVE) or 2-vinyloxyethyl methacrylate (VEMA)] were introduced into the above THF solution of the copolymer at 20°C. Every side chain of AEEMA unit of poly(MMA-co-AEEMA) was activated by EtAlCl₂ to induce the cationic polymerization of the functional monomer. THF, which was used as solvent in the preparation of the copolymer of MMA and AEEMA, acted as a Lewis base in the latter cationic polymerization, thus stabilizing the propagating site. By using this procedure, a controlled cationic polymerization of a functional monomer was achieved and a well-defined graft copolymer with functional side chains was obtained. Instead of a single functional monomer, the simultaneous addition of isobutyl vinyl ether (IBVE) and AcVE, ClVE or VEMA during the second step cationic polymerization process generated a graft copolymer with random copolymer side chains. Furthermore, a graft copolymer with block side chains could also be prepared by performing a block copolymerization during the second cationic grafting step by adding sequentially AcVE (ClVE or VEMA) and IBVE or vice versa. Every graft copolymer thus obtained possessed a high purity, controlled graft number and molecular weight as well as a narrow molecular weight distribution (M_w/M_n = 1.12 ˜ 1.25).