Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 9. Radical Coupling Reaction of 1,1‐Diphenylethylene‐Functionalized Polymers with Potassium Naphthalenide and Its Application to Syntheses of In‐Chain‐Functionalized Polymers and Star‐Branched Polymers

Radical coupling reactions of both 1,1‐diphenylethylene (DPE)‐chain‐end‐ and DPE‐in‐chain‐functionalized polymers with potassium naphthalenide have been studied under the conditions mainly in THF at –78°C. Chain‐end‐functionalized polymers having M̄_n values of less than 10 kg/mol were very efficiently coupled in more than 90% yield to afford the polymeric dianion that were dimeric coupled products with two 1,1‐diphenylalkyl anions in the middle of the chains. However, the dimer yield decreased with increasing the molecular weight. The dimer was obtained in 59% yield with use of the chain‐end‐functionalized polymer having M̄_n of 33.9 kg/mol. Well‐defined in‐chain‐functionalized polymers with two benzyl bromide and DPE moieties each have been successfully synthesized by the reaction of the polymeric dianion thus obtained with 1‐(4‐bromobutyl)‐4‐(tert‐butyldimethylsilyloxymethyl)benzene and 1‐[4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene, respectively. The radical coupling reaction of in‐chain‐functionalized polymers with DPE (M̄_n ca. 20 kg/mol) with potassium naphthalenide also proceeded efficiently to afford the coupled products that were A₂A′₂ and A₂B₂ four‐arm star‐branched polymers with well‐defined structures (M̄_n ca. 40 kg/mol).     

Synthesis of Branched Polymers by Means of Living Anionic Polymerization, 8. Synthesis of Well‐Defined Star‐Branched Polymers by an Iterative Approach Based on Living Anionic Polymerization Using 1,1‐Diphenylethylene Derivatives

The synthesis of well‐defined four‐ and six‐arm star branched polymers in which arms differ either in molecular weight or composition has been achieved via a new iterative approach based on living anionic polymerization using 1,1‐diphenylethylene (DPE) derivatives. Each stage in the iteration involves two reactions: a living functionalization reaction of living anionic polymer with DPE derivatives and an in‐situ reaction of the resulting linked product having two anions with 1‐4‐(4‐bromobutyl)phenyl]‐1‐phenylethylene to introduce two DPE moieties into the polymer. In each living functionalization reaction, a 1.2‐fold excess or more of living anionic polymer relative to DPE moiety was employed to complete the reaction. Asymmetric A₂A′₂ and A₂A′₂A′′₂ star‐branched polystyrenes as well as A₂B₂ and A₂B₂C₂ heteroarm star‐branched polymers were synthesized by repeating the iteration synthetic sequence two and three times, respectively. Since the polymers obtained by each reaction stage were contaminated with their precursor polymers, they were isolated by SEC fractionation. Their high degrees of compositional, molecular weight and architectural homogeneity were confirmed by the analytical results of SEC, SLS, VPO, ¹H NMR and viscosity measurements.     

Relationship between Architecture and Adhesive Properties of Macromolecular Materials, 1

This study deals with the preparation of polyurethane‐graft‐poly(n‐butyl acrylate)s copolymers by polymerization of diphenyl‐methane‐4,4‐di‐isocyanate (MDI) with α,α′‐di‐hydroxyl‐poly(n‐butyl acrylate)s of different sizes as macromonomers. The polyaddition has been studied on the basis of kinetic measurements, and the comb‐like structure of the resulting polymer has been well‐established. Such grafted copolymers display specific adhesive properties in connection with their comb‐like architecture.

     

Successive Synthesis of Multiarmed and Multicomponent Star‐Branched Polymers by New Iterative Methodology Based on Linking Reaction between Block Copolymer In‐Chain Anion and α‐Phenylacrylate‐Functionalized Polymer

A series of multiarmed and multicomponent miktoarm (μ‐) star polymers have been successfully synthesized by developing a new iterative methodology based on a specially designed linking reaction of the block copolymer in‐chain anions, whose anions are positioned between the blocks, with α‐phenylacrylate (PA)‐functionalized polymers. The iterative methodology involves the following two reaction steps: a) introduction of two different polymer segments by the linking reaction of a block copolymer in‐chain anion with a PA‐functionalized polymer and b) regeneration of the PA reaction site. By repeating this reaction sequence, two different polymer segments are advantageously and successively introduced into the μ‐star polymer. In practice, repetition of the reaction sequence affords well‐defined 3‐arm ABC, 5‐arm ABCDE, 7‐arm ABCDEFG, and even 9‐arm ABCDEFGHI μ‐star polymers, composed of polystyrene, polystyrenes substituted with functional groups, polyisoprene, and poly(alkyl methacrylate) arms, respectively.

     

Lingo‐1 Inhibited by RNA Interference Promotes Functional Recovery of Experimental Autoimmune Encephalomyelitis

Lingo‐1 is a negative regulator of myelination. Repairment of demyelinating diseases, such as multiple sclerosis (MS)/experimental autoimmune encephalomyelitis (EAE), requires activation of the myelination program. In this study, we observed the effect of RNA interference on Lingo‐1 expression, and the impact of Lingo‐1 suppression on functional recovery and myelination/remyelination in EAE mice. Lentiviral vectors encoding Lingo‐1 short hairpin RNA (LV/Lingo‐1‐shRNA) were constructed to inhibit Lingo‐1 expression. LV/Lingo‐1‐shRNA of different titers were transferred into myelin oligodendrocyte glycoprotein‐induced EAE mice by intracerebroventricular (ICV) injection. Meanwhile, lentiviral vectors carrying nonsense gene sequence (LVCON053) were used as negative control. The Lingo‐1 expression was detected and locomotor function was evaluated at different time points (on days 1,3,7,14,21, and 30 after ICV injection). Myelination was investigated by luxol fast blue (LFB) staining.LV/Lingo‐1‐shRNA administration via ICV injection could efficiently down‐regulate the Lingo‐1 mRNA and protein expression in EAE mice on days 7,14,21, and 30 (P < 0.01), especially in the 5 × 10⁸ TU/mL and 5 × 10⁹ TU/mL LV/Lingo‐1‐shRNA groups. The locomotor function score in the LV/Lingo‐1‐shRNA treated groups were significantly lower than the untreated or LVCON053 group from day 7 on. The 5 × 10⁸ TU/mL LV/Lingo‐1‐shRNA group achieved the best functional improvement (0.87 ± 0.11 vs. 3.05 ± 0.13, P < 0.001). Enhanced myelination/remyelination was observed in the 5 × 10⁷, 5 × 10⁸, 5 × 10⁹ TU/mL LV/Lingo‐1‐shRNA groups by LFB staining (P < 0.05, P < 0.01, and P < 0.05).The data showed that administering LV/Lingo‐1‐shRNA by ICV injection could efficiently knockdown Lingo‐1 expression in vivo, improve functional recovery and enhance myelination/remyelination. Antagonism of Lingo‐1 by RNA interference is, therefore, a promising approach for the treatment of demyelinating diseases, such as MS/EAE. Anat Rec, 297:2356–2363, 2014. © 2014 Wiley Periodicals, Inc.     

Complex Branched Polyolefin Generated from Quasi‐living Polymerization of 4‐Methyl‐1‐pentene Catalyzed by α‐Diimine Palladium Catalyst

Branched α‐olefin 4‐methyl‐1‐pentene (4MP) is polymerized with a cationic α‐diimine palladium catalyst. The influences of polymerization parameters including reaction temperature and monomer concentration on polymer architecture are evaluated in detail. Increasing temperature and lowering monomer concentration can lead to the formation of more complex branched polyolefin because of chain walking. At 0 °C, complex branched polyolefins are generated from quasi‐living polymerization of 4MP with α‐diimine palladium catalyst.

     

Chain Extension of Carboxy‐Terminated Aliphatic Polyamides and Polyesters by Arylene and Pyridylene Bisoxazolines

Summary: The bulk reactions between carboxy‐terminated polyamide‐12 ( PA12 ) or carboxy‐terminated poly(butane‐1,4‐diyl adipate) ( PBDA ) and 2,2′‐(1,3‐phenylene)bis(2‐oxazoline) ( mbox ), 2,2′‐(1,4‐phenylene)bis(2‐oxazoline) ( pbox ), 2,2′‐(2,6‐pyridylene)bis(2‐oxazoline) ( pybox ) as chain‐coupling agents were studied by size exclusion chromatography, carboxy end‐group titration, and NMR spectroscopy. The chain‐coupling reaction yielded high‐molar mass polymers within 20 to 180 min, depending on reaction temperature, starting oligomer molar mass, bisoxazoline/oligomer molar ratio, and the nature of bisoxazoline. No side‐reactions were observed. Bisoxazoline pybox , used for the first time in the bulk chain extension of carboxy‐terminated polymers, exhibited the highest reaction rates. The thermal properties of the resulting polymers, studied by differential scanning calorimetry and thermogravimetric analysis, are also discussed.

The reaction of PBDA and PA12 with mbox , pbox , and pybox to give rise to the polymers studied here.     

Synthesis,Characterization, and Investigation of Thermosensitive Star‐Shaped Poly(2‐isopropyl‐2‐oxazolines) Based on Carbosilane Dendrimers

Star‐shaped poly(2‐isopropyl‐2‐oxazolines) with dramatically hydrophobic dendrimer core are synthesized using carbosilane dendrimers of first to third generations as macroinitiators. It is observed that half of the initiator functional groups are incorporated in polymerization process. The polymerization degree of polyoxazoline arms is about 25. Strong arm folding results in small molecule dimensions in both aqueous and organic solutions. Thermosensitive properties are studied for second generation‐based star solution with the concentration of 0.00095 g cm⁻³. Model linear poly(2‐isopropyl‐2‐oxazolines) are investigated for comparison. Carbosilane dendrimer core interaction leads to the formation of different types of aggregates at low temperatures. The temperatures of the beginning (T ₁ = 42–43 °C) and finishing (T ₂ = 50 °C) of phase separation are determined. It is shown that macromolecule compactization and aggregation take place even far from the phase transition interval and alternately prevail on heating.

     

Synthesis,Self‐Assembly,and Properties of Homoarm and Heteroarm Star‐Shaped Inorganic–Organic Hybrid Polymers with a POSS Core

Novel homoarm and heteroarm star‐shaped inorganic–organic hybrid polymers with a polyhedral oligomeric silsesquioxane (POSS) core are prepared via click chemistry of azide POSS [POSS‐(N₃)₈], alkynyl poly(L ‐lactide) (PLLA), and alkynyl poly(ethylene oxide) (PEO). The melting and crystallization behaviors of the polymers can be adjusted by altering the PLLA to PEO ratio. The hybrid polymers reveal unique crystalline morphology due to the influence of the star‐shaped structure and the mutual influence of PLLA and PEO. The hybrid polymers show different thermostabilities, owing to the different compositions of the polymers. The hydrophilicity can be adjusted by alternating the composition of the PLLA and PEO segments. In addition, the sizes of the polymer micelles change with the change of the ratio of PLLA and PEO arms in the hybrid polymers.

     

Preparation,Characterization, and Rheological Behaviors of Polysiloxanes Presenting Densely Simple and Well‐Defined Short‐Branched Chains

In this paper, a series of polysiloxanes, presenting different contents of densely simple and well‐defined short‐branched chains (G₁–G₅), are prepared by hydrosilylation of α,ω‐(dimethylvinylsiloxy)‐poly(dimethyl‐methylvinyl)siloxanes (P₁–P₅) with 1,1,1,3,5,5,5‐heptamethyltrisiloxane (MD^HM) and characterized by ¹H and ²⁹Si nuclear magnetic resonance, Fourier transform‐infrared spectroscopy, Abbe refractometry, gel permeation chromatography, and differential scanning calorimetry. The rheological behaviors of the G₁–G₅ products are investigated to study the influences of the short‐branched chains. The rheological parameters including non‐Newtonian index (n ) and the flow activation energy (ΔE_η ) are obtained and discussed. It is observed that the G₁–G₅ polymers belonged to pseudoplastic fluids and the ΔE_η values of the G₁–G₅ products are significantly influenced by the short‐chain branching degree of the polymers.

     

Structure‐Property Relationships of Linear and Long‐Chain Branched Metallocene High‐Density Polyethylenes Characterized by Shear Rheology and SEC‐MALLS

Summary: Linear and long‐chain branched high‐density polyethylenes with a molar mass between 1 700 and 1 150 000 g · mol^?1 were synthesized using metallocene catalyst systems. Depending on the polymerization parameters the molar mass distribution reached values ranging from 2 to 12. The resins were characterized with various analytical methods. The branch detection took place via two independent methods, melt rheology and SEC‐MALLS. New relationships between catalyst structure, polymerization conditions, and the branching content of polyethylenes were established. Besides the branched materials strictly linear polymers are presented; for those no long‐chain branches were detected either by light scattering or by rheology. The viscosity function was observed to be strongly influenced by the molar mass distribution and the degree of long‐chain branching. The molar mass distribution was affected by the catalyst type and the polymerization conditions. A dependence of the melting point and the melting enthalpy on the molar mass was observed.

η₀‐ correlation of the linear and long‐chain branched samples.     

Enhancement of Experimental Anaerobic Infections by Blood, Hemoglobin, and Hemostatic Agents

Certain foreign materials have been demonstrated to enhance the infectivity of aerobic and anaerobic bacteria. Whole blood and other protein compounds encountered in surgical settings or trauma were tested for their effect on infectivity of nonsporeforming anaerobic bacteria. Infectious synergistic mixtures of Bacteroides fragilis plus Peptostreptococcus anaerobius and Bacteroides melaninogenicus plus Fusobacterium necrophorum were each diluted to a barely noninfectious or minimally infectious concentration (subinfective inoculum) that was injected intraperitoneally into mice alone and in combination with test proteins. Infectivity was measured by deaths from sepsis or abscess(es) within the abdominal cavity at autopsy at 1 week. Two hemostatic agents, Gelfoam powder and Avitene (final concentrations, 10 mg/ml), and crystalline hemoglobin (4 g/100 ml) each produced a marked increase (P < 0.001) in the rate of infection when mixed with a normally subinfective inoculum of either bacterial mixture. Fresh homologous mouse blood (0.25 ml) injected intraperitoneally without anticoagulant also significantly enhanced infectivity (P < 0.01) of a subinfective inoculum of B. fragilis plus P. anaerobius. These studies demonstrated the capacity of whole blood, hemoglobin, and hemostatic agents to enhance the infectivity of certain nonsporeforming anaerobic bacteria. The high concentrations of anaerobic bacteria in the gastrointestinal, female genital, and respiratory tracts produce an increased risk of human infection after surgery or trauma in these sites; the protein agents studied here may further enhance infection.     

BNIP‐2 binds phosphatidylserine,localizes to vesicles,and is transported by kinesin‐1

BNIP‐2 shows high homology with the Cayman ataxia protein, caytaxin, which functions as a kinesin‐1 adapter bridging cargos and kinesin light chains (KLCs). BNIP‐2 is known to induce cell shape changes when over‐expressed in culture cells, but its physiological functions are mostly unknown. BNIP‐2 interacts with KLC through the conserved WED motif in the N‐terminal region of BNIP‐2. Interaction with KLC and transportation by kinesin‐1 are essential for over‐expressed BNIP‐2 to elongate cells and induce cellular processes. Endogenous BNIP‐2 localizes to the Golgi apparatus, early and recycling endosomes and mitochondria, aligned with microtubules, and moves at a speed compatible with kinesin‐1 transportation. The CRAL–TRIO domain of BNIP‐2 specifically interacts with phosphatidylserine, and the vesicular localization of BNIP‐2 requires interaction with this phospholipid. BNIP‐2 mutants which do not bind phosphatidylserine do not induce morphological changes in cells. These data show that similar to caytaxin, BNIP‐2 is a kinesin‐1 adapter involved in vesicular transportation in the cytoplasm and that association with cargos depends on interaction of the CRAL–TRIO domain with membrane phosphatidylserine.     

Synthesis,Characterization and Behavior in Aqueous Solution of Star‐Shaped Poly(acrylic acid)

Summary: We report the synthesis of star‐shaped poly(acrylic acid) (PAA), with 5, 8, and 21 arms, by atom transfer radical polymerization of tert‐butyl acrylate. We employ the core‐first approach using glucose‐, saccharose‐ and cyclodextrin‐based initiators. Subsequent acidic treatment of poly(tert‐butyl acrylate) (PtBA) leads to star‐shaped poly(acrylic acid) (PAA). Alkaline cleavage of the arms enabled us to determine the initiation site efficiency. The PAA stars and arms were esterified to poly(methyl acrylate) (PMA). Molecular weight determination by means of GPC/viscosity, MALDI‐TOF MS and NMR end‐group determination showed that the initiation site efficiency is close to unity. Results from potentiometric titration of PAA arms and stars show that the apparent pK_a values increase with increasing arm number, which is a direct result of increasing segment density. Osmometry measurements of aqueous solutions of the PAA stars result in osmotic coefficients between 0.05 and 0.38, indicating that most of the counterions are confined within the star. The confinement increases with arm number.

Potentiometric titration curves for stars (PAA₁₀₀)₂₁, (PAA₁₀₀)₈, (PAA₁₀₀)₅, and linear PAA₁₀₀.     

Control of the radical polymerization by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl and its sodium salt

The control of the radical polymerization of styrene by 2,2,15,15‐tetramethyl‐1‐aza‐4,7,10,13‐tetraoxacyclopentadecan‐1‐oxyl is reported here in bulk at 90 °C, 120 °C and in miniemulsion. Similarly, the control by its sodium complex is reported in bulk at 90 °C.

M _n vs. conversion for 3 , 3Na , and TEMPO.     

Tunable Nanometer‐Scale Architecture of Organic–Inorganic Hybrid Nanostructured Materials for Structural and Functional Applications

Direct crystallization of polymer crystals along the long axis of carbon nanotubes (CNTs) to produce a hybrid nanostructured material is expected to retain the properties of CNTs and has the advantage of a strong polymer/CNT interface. Three different polymer systems are selected to elucidate the fundamental principles that govern the processing of organic–inorganic hybrid nanostructured materials with nanometer‐scale architecture. The tunable character of the nanometer‐scale hybrid architecture is investigated as a function of undercooling and polymer concentration. It is observed that while polyethylene and nylon 6,6 crystallize in a periodic manner as disk‐shaped crystals along the long axis of the CNTs, the polypropylene–CNTs result in conventional spherulites. The reasons for these differences are analyzed.     

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.