Monolayer Assemblies of Comb Polymers Containing Different Kinds of Fluorocarbon Side‐Chains

Summary: Langmuir monolayers and organized molecular films of comb polymers containing different kinds of fluorocarbon side‐chains with various chain lengths and substituted atoms at the ω‐position were characterized by surface pressure‐area isotherms as well as Brewster angle microscopy on a water surface and by scanning probe microscopies (AFM and FFM) and the out‐of and in‐plane X‐ray diffractions on the solid substrates, respectively. When compared with monolayers of fluorinated amphiphilic vinyl monomers, those of the corresponding comb polymers were significantly stabilized. The nanostructures of these organized molecular films changed considerably with the film fabrication method used (such as mixed monolayers with hydrogenated amphiphiles) and the deposition conditions as well as with minor chemical modification of the fluorinated comb polymers with different hydrophilic esters and fluorocarbon side‐chains. The characteristic friction behavior for films built up of the fluorinated amphiphiles and comb polymers was found to depend strongly on the chemical constituents of the outermost layer of the film surface.

     

Chemical Synthesis of Polyaniline Inverse Opals by Templating Colloidal Crystals in the Presence of Dodecylbenzenesulfonic Acid

A simple method for chemically synthesizing PANI inverse opals by templating colloidal crystals is presented. The use of dodecylbenzene sulfonic acid resulted in structures with reduced shrinkage, allowing the position of the optical stop band to be tuned. The conductivity of the inverse opals was increased, and that of PANI was estimated to be 8 S · cm^?1. The inverse opals were of good structural integrity and fidelity, and the overall thickness could be controlled by that of the templates. Optical reflection spectra provided additional evidence of the high crystalline quality of the samples. These inverse opals might be attractive materials for sensor applications and studies of novel optical properties.

     

Intrinsic Viscosity of Aqueous Solutions of Carboxymethyl Guar in the Presence and in the Absence of Salt

Intrinsic viscosities were determined for solutions of CMG in pure water and 0.9 wt.‐% aqueous NaCl. To avoid the 0/0‐type extrapolation typical for Huggins plots, a new procedure was used. For CMG and pure water, this requires only two adjustable parameters: the specific hydrodynamic volume of the polymer in the limit of infinite dilution and a hydrodynamic interaction parameter. The intrinsic viscosity of CMG (no salt) at room temperature is 6 050 mL · g^?1; approximately half as large as that of Na‐PSS of comparable molar mass. The ratio of the intrinsic viscosities with and without salt is ≈7 for CMG, as compared to >100 for Na‐PSS. The reasons for the different behaviors of the two types of polyelectrolytes are being discussed.

     

Polyrotaxanes of Pyrene–Triazole Conjugated Azomethine and α‐Cyclodextrin with High Fluorescence Properties

The paper reports on the preparation of a new 2‐rotaxane monomer through an acid coupling reaction between 1‐pyrenecarboxaldehyde and α‐CD/3,5‐diamino‐1,2,4‐triazole inclusion complex. Pyrenyl groups are large enough to provide a blocking effect toward cyclodextrin de‐threading. The oxidative C? C coupling of 2‐rotaxane in the presence of RuCl₃ catalyst afforded conjugated azomethine polyrotaxanes. The expected modifications of the solubility, morphology, film forming ability for rotaxane polymer were proved. As shown by fluorescence and UV‐vis spectroscopy, a material with optical properties appropriate for use in photonics was obtained.

     

A Study of Copolymerization of 1‐Hexene with 2,5‐Norbornadiene Using Metallocene Catalysts

Summary: Copolymerization of 1‐hexene with a symmetrical diene, namely 2,5‐norbornadiene was studied using four different metallocene catalysts. Copolymerization was found to occur exclusively through one of the two equally reactive endocyclic double bonds with all the four catalysts. Copolymerization results in low molecular weight oligomers with the number average molecular weight ( ) varying from 1 000–3 000. End group analysis of the co‐oligomers revealed that the β‐hydrogen transfer after 2,1 insertion also occurs in the presence of highly regiospecific catalysts. The regio errors were also found to depend on various reaction parameters such as polymerization time, Al/Zr mol ratio, metallocene concentration and polymerization temperature.

Plots of variation in end groups and NBD incorporation with time.     

Synthesis,Crystallization, and Enzymatic Degradation of the Biodegradable Polyester Poly(ethylene azelate)

Poly(ethylene azelate) (PEAz) was synthesized and its melting behavior was studied with DSC and Step Scan DSC. The equilibrium melting point of PEAz was found 62 °C and the heat of fusion of 100% crystalline polymer was estimated at 160 J · g^?1. Polarized light microscopy showed mixed birefringence. From isothermal crystallization DSC study, after self‐nucleation, crystallization rates were estimated. The Lauritzen–Hoffman plots showed crystallization regime I to II and II to III transition at 34 and 19 °C respectively. Non‐isothermal crystallization was studied. The activation energy was calculated applying the isoconversional method of Friedman. Chemical hydrolysis of PEAz was very slow, while enzymatic hydrolysis showed comparable rates with PCL.

     

Perfluoropolyether structures as surface modifying agents of UV-curable systems

New functionalised macromers containing perfluoropolyether (PFPE) structures and methacrylic end groups were synthesised and used as modifying additives for acrylic UV-curable systems. Their chemical structure is Rh-Rf-Rh, where and with p ≈ q. Notwithstanding their very low concentration, below 0.5 wt.-%, the fluorinated macromers cause a dramatic change of the surface properties of the films, without changing their curing conditions and their bulk properties. X-ray photoelectron spectroscopy (XPS) measurements showed that the macromers are able to concentrate selectively at the surfaces of the films, depending on their chemical structure and on the kind of substrate employed.     

Thermal Properties of Poly(ester amide)s with Isolated,Two Adjacent and Three Adjacent Amide Groups within a Polyester Chain

Differential scanning calorimetry (DSC) was employed to investigate the thermal properties of segmented aliphatic poly(ester amide)s (PEA)s. Three different series of PEAs were synthesized, each containing amide blocks of defined lengths which are randomly placed in the poly(butylene adipate) (PBA) backbone. Thus, the defined amide blocks consist of isolated amide groups, two adjacent amide groups or three adjacent amide groups. The PEAs show glass transition temperatures between ?63 and 1 °C, melting temperatures between 28 and 183 °C and crystallization temperatures lie between ?0.2 and 148 °C. The types of groups participating in the crystallization process and the length of the amide segments have an influence on the morphology of these polymers.

     

Microwave‐Assisted Synthesis of Poly(L‐lactic acid) via Direct Melt Polycondensation Using Solid Super‐Acids

A microwave‐assisted method of synthesizing high‐molecular‐weight PLA using SSA as green catalyst was developed. Yellowish PLA with above 2.0 × 10⁴ g · mol^?1 was obtained when the reaction was run at 260 °C within 60 min under microwave irradiation with 0.4 wt.‐% SSA. This method used only 10% of the energy consumption necessary for conventional heating, and the catalyst could be used five times without losing catalytic activity. The improvement in and the decrease in the energy consumption under microwave irradiation suggested that selective heating and hot spots effects played a crucial role. The method was shown to be a time‐saving, green and a promising way to lower the cost and spread the application of PLA.

     

UV‐Curable Organic‐Inorganic Hybrid Film Coatings Based on Epoxidized Cyclohexene Derivatized Linseed Oil

Summary: Organic‐inorganic hybrid films based on epoxidized cyclohexene derivatized linseed oil (ECLO) and tetraethylorthosilicate (TEOS) oligomers were prepared via a UV‐curing process. The kinetics of the hybrid materials were studied by photo‐differential scanning calorimetry (DSC). In addition to the kinetics, the tensile properties, pencil hardness, pull‐off adhesion, reverse impact resistance, solvent resistance and abrasion resistance of the hybrid coatings were evaluated. Both dynamic mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA) were used to investigate the viscoelastic and thermal properties of the hybrid films. The morphology of the hybrid film was characterized by atomic force microscopy (AFM). Based on the results from the aforementioned evaluation of the coatings, the hybrid films exhibited higher pencil hardness, tensile strength, tensile modulus, fracture toughness, abrasion resistance, cross‐link density and thermal stability compared to the ECLO organic film. The Photo‐DSC data showed that the photo‐curing speed of the hybrid materials increased with TEOS oligomers content. It was postulated that the TEOS oligomers were reactive diluents.

Structure of ECLO.     

Sulfonation of Poly(propylene) Films with Fuming Sulfuric Acid

Summary: Sulfonation is one of the most commonly used methods for the surface modification of polymers. In this study, the sulfonation of poly(propylene) (PP) films with fuming sulfuric acid has been investigated with the focus on the surface reaction. Analysis of the sulfonated PP films by X‐ray photoelectron spectroscopy (XPS), attenuated total reflectance (ATR) infrared spectroscopy, and chemical modification demonstrated the formation of C?C double bonds and sulfate groups in the sulfonation process. These results and a comparison with low‐density polyethylene (LDPE) films led us to propose a new sulfonation mechanism involving hydride abstraction and the formation of β‐sultones.

The here proposed mechanism of the sulfonation of poly(propylene) involves the formation of unstable β‐sultones.     

Cholesteric Liquid‐Crystalline Side‐on Polysiloxanes: Effects of Biaxiality on the Cholesteric Structure

Summary: Biaxial side‐on cholesteric copolysiloxanes with laterally attached mesogenic groups were investigated in mixtures with a low molar mass liquid crystal. While mixtures with a low concentration of the polymer exhibit the conventional fingerprint texture, for concentrations above about 60 mol‐% characteristic irregularities appear in the cholesteric structure that are obviously due to phase biaxiality. Besides the absence of pseudo‐isotropic lines, irregular patterns perpendicular to the helix axis emerge and the periodic distance of regions with similar optical properties along the helix axis is strongly disturbed. This suggests that the photonic band gap width of a uniaxial cholesteric phase becomes strongly affected when a phase transformation into a biaxial cholesteric phase occurs.

Cholesteric fingerprint texture of a mixture of uniaxial nematic monomer and biaxial cholesteric polymer.     

Investigation of Templated Mesoporous Silicate Thin Films Using High Speed,Solid‐State 1H MAS and Double Quantum NMR Spectroscopy

Two‐dimensional DQ ¹H MAS NMR has been used the investigate the local structure of a surfactant‐templated silicate thin film prepared from adding 4% polyoxyethylene(10) cetyl ether to an acidic TEOS silica sol. A close spatial contact between the surfactant and the silicate present in these materials could be demonstrated, while the high sensitivity of the NMR experiments allowed systems with limited amounts of material to be investigated. The detected inorganic‐organic interactions in these materials provide additional information into the chemical processes occurring during the self‐assembly process and the formation of meso‐structured materials.

Graphical representation of the spatial interactions observed between the silanols, oxomethylene protons of the surfactant and water within the template silicate material.     

Photoinitiated Cationic Polymerization of Substituted Vinylcyclopropanes

Summary: The photoinitiated cationic polymerization of 1‐cyclopropyl‐l‐phenyl‐ethylene, 1‐cyclopropyl‐l‐(p‐methoxyphenyl)ethylene and 1‐cyclopropyl‐l‐(p‐fluorophenyl)ethylene at ambient temperatures in bulk and in solution was investigated using (η⁵‐2,4‐cyclopentadiene‐l‐yl)[l,2,3,4,5,6‐η] (l‐(methylethyl) benzene)iron(I) hexafluorophosphate (Irgacure 261, I‐1 ) and ditolyliodonium hexafluorophosphate ( I‐2 ). In contrast to our results in the polymerization of 2‐cyclopropyl‐4‐methylene‐l,3‐dioxolanes, partial ring‐opening of the cyclopropane ring could be detected. A volume shrinkage of about 11% was found.

     

Metathetic Selective Degradation of Polyisoprene: Low‐Molecular‐Weight Telechelic Oligomer Obtained from Both Synthetic and Natural Rubber

Summary: Degradation studies of cis‐1,4‐polyisoprene were carried out using first and second generation Grubbs catalysts to achieve end‐functionalized acetoxy oligomers in both an organic solvent and a latex phase at room temperature. Well‐defined acetoxy telechelic polyisoprene structures were obtained in a selective manner with a range of from 10 000 to 30 000, with a polydispersity index of around 2.5.

Structure produced by the metathetic depolymerization of hydroxy telechelic cis‐1,4‐polyisoprene.     

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.     

Negatively Birefringent Polymer Films

Polymer films exhibiting large negative birefringence, suitable for compensating residual positive birefringence of liquid crystal displays, have been achieved for syndiotactic polystyrene. Procedures involving axial stretching at different draw ratios of unoriented films, followed by different crystallization routes, have been compared. The control of the polymer polymorphic behavior, i.e., of the formation of crystalline and co‐crystalline (with low‐molecular‐mass guest molecules) phases, allows to control the negative birefringence up to Δn = n_? ? n_|| = 0.17.

     

Thermally Reversible Cross‐Linked Polyamides with High Toughness and Self‐Repairing Ability from Maleimide‐ and Furan‐Functionalized Aromatic Polyamides

Polyamides having various amounts of maleimide (PA‐MI) and furan (PA‐F) pendent groups, respectively, as well as their cross‐linked polymers (PA‐MI/PA‐F) were prepared. PA‐MI/PA‐F cross‐linked polymers showed thermally reversible cross‐linking behavior via Diels‐Alder (DA) and retro‐DA reactions. Cross‐linked PA‐MI/PA‐F films exhibited enhanced toughness and mechanical properties compared to PA‐MI and PA‐F precursors. Moreover, PA‐MI/PA‐F films also showed thermal self‐repairing behavior, which was observed in the micrographs and instron tests.

     

Crystal Growth in Poly(L‐lactide) Thin Film Revealed by in situ Atomic Force Microscopy

Direct visualization of crystal growth in poly(L ‐lactide) thin films was carried out by using a temperature‐controlled atomic force microscopy (AFM). At the initial stage of crystallization, edge‐on lamellar crystals have nucleated and elongated. Subsequently, the edge‐on lamellar crystals showed S‐shaped morphology and changed their orientation from edge‐on manner to flat‐on one. The curvature of edge‐on lamellar crystal has been discussed in terms of inclination and distortion of polymer chains in the crystal. In addition, mechanism on the formation of flat‐on crystal from edge‐on lamellae was proposed as derivative growth on the basis of in situ AFM observation of crystal growth and enzymatic degradation.

     

Back‐Biting Termination in Methyl Methacrylate/tert‐Butyl Acrylate Anionic Block Copolymerization

The product of spontaneous termination formed after addition of one or two t‐BuA units onto living PMMA chains in the MMA/t‐BuA block copolymerization was isolated and characterized by SEC, UV, FT‐IR, Raman and NMR spectroscopy. It appears as a low‐molecular‐weight peak in SEC eluograms of the copolymers, absorbing at 260 nm; its retention time corresponds to that of the PMMA block. In its FT‐IR and Raman spectra, new bands appeared corresponding to the C?C and C?O vibrations of a conjugated and H‐bonded ester group of the enol form of the cyclic oxoester composed of MMA and t‐BuA units. Experimental support of a back‐biting reaction at the link between PMMA and Pt‐BuA blocks is presented.