Double‐Gyroid Morphology of a Polystyrene‐block‐Poly(ferrocenylethylmethylsilane) Diblock Copolymer: A Route to Ordered Bicontinuous Nanoscale Architectures

A polystyrene‐block‐poly(ferrocenylethylmethylsilane) diblock copolymer, displaying a double‐gyroid morphology when self‐assembled in the solid state, has been prepared with a PFEMS volume fraction ?_PFEMS = 0.39 and a total molecular weight of 64 000 Da by sequential living anionic polymerisation. A block copolymer with a metal‐containing block with iron and silicon in the main chain was selected due to its plasma etch resistance compared to the organic block. Self‐assembly of the diblock copolymer in the bulk showed a stable, double‐gyroid morphology as characterised by TEM. SAXS confirmed that the structure belonged to the Ia d space group.

     

Amphiphilic Block Copolymers Containing Regioregular Poly(3‐hexylthiophene) and Poly(2‐ethyl‐2‐oxazoline)

Poly(3‐hexylthiophene)‐block‐poly(2‐ethyl‐2‐oxazoline) amphiphilic rod–coil diblock copolymers have been synthesized by a combination of Grignard metathesis (GRIM) and ring‐opening cationic polymerization. Diblock copolymers containing 5, 15, and 30 mol‐% poly(2‐ethyl‐2‐oxazoline) have been synthesized and characterized. The synthesized rod–coil block copolymers display nanofibrillar morphology where the density of the nanofibrills is dependent on the concentration of the poly(2‐ethyl‐2‐oxazoline) coil segment. The conductivity of the diblock copolymers was lowered from 200 to 35 S · cm^?1 with an increase in the content of the insulating poly(2‐ethyl‐2‐oxazoline) block. By contrast, the field‐effect mobility decreased by 2–3 orders of magnitude upon the incorporation of the poly(2‐ethyl‐2‐oxazoline) insulating segment.

     

Synthesis and Characterization of Amphiphilic Poly(ethylene oxide)‐block‐poly(hexyl methacrylate) Copolymers

We describe the preparation of amphiphilic diblock copolymers made of poly(ethylene oxide) (PEO) and poly(hexyl methacrylate) (PHMA) synthesized by anionic polymerization of ethylene oxide and subsequent atom transfer radical polymerization (ATRP) of hexyl methacrylate (HMA). The first block, PEO, is prepared by anionic polymerization of ethylene oxide in tetrahydrofuran. End capping is achieved by treatment of living PEO chain ends with 2‐bromoisobutyryl bromide to yield a macroinitiator for ATRP. The second block is added by polymerization of HMA, using the PEO macroinitiator in the presence of dibromobis(triphenylphosphine) nickel(II), NiBr₂(PPh₃)₂, as the catalyst. Kinetics studies reveal absence of termination consistent with controlled polymerization of HMA. GPC data show low polydispersities of the corresponding diblock copolymers. The microdomain structure of selected PEO‐block‐PHMA block copolymers is investigated by small angle X‐ray scattering experiments, revealing behavior expected from known diblock copolymer phase diagrams.

SAXS diffractograms of PEO‐block‐PHMA diblock copolymers with 16, 44, 68 wt.‐% PEO showing spherical (A), cylindrical (B), and lamellae (C) morphologies, respectively.     

Organic–Inorganic Interactions in Poly(trimethylene carbonate)–Titania Hybrids

Polycarbonate–titania hybrids have been synthesized by a sol–gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT‐IR spectra reveal the presence of Ti O C covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that Ti O C bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO₂ domains, confirmed by atomic force microscopy, provides optically transparent hybrids.

     

Preparation of Positively and Negatively Charged Organic Colloids from a Single Precursor

A synthetic route is presented for the preparation of electrically charged colloidal particles with either sign from the same precursor. In the first step, methyl methacrylate was copolymerized with ω‐bromoalkyl acrylate and a cross‐linker, leading to monodisperse, bromo‐functionalized colloids. Substitution of the bromo‐functions by either trimethylamine or Na₂SO₃ transformed the neutral precursors into positively or negatively charged particles, respectively. The charge density could be varied in two ways: (i) by varying the fraction of bromo‐functionalized monomers; (ii) by increasing the degree of substitution of the bromo‐functions. Derivation of the charged particles from the same precursor colloid made it easier to explain various interesting physical properties of the charged colloidal particles. Higher charge densities were achieved for the cationic colloids. If a threshold value for the charge density of 55 μC · cm^?2 was surpassed, the particles showed a significant swelling in aqueous solution.

     

UV Laser Deposition of SiS/Poly(thiacarbosilane) Composites and their Conversion to SiO/Poly(thiacarbosiloxane) Composites

ArF laser irradiation of gaseous mixtures of carbon disulfide and silane allows efficient deposition of Si? S bond‐containing poly(thiacarbosilanes) incorporating SiS bodies. These SiS/poly(thiacarbosilane) composites are the first example of silicon sulfide/polymer composites. Composite formation is analyzed by GC/MS analysis of volatile products and the structure of the composite as determined by electron microscopy and FT‐IR spectra. The composites undergo reaction with air moisture and methanol vapor, evolve H₂S and evolve to nano‐sized poly(thiacarbosiloxane)s and poly(methoxythiacarbosiloxane)s.

     

Synthesis of Polyphenylene Ether Derivatives: Estimation of Their Dielectric Constants

A series of poly(2‐alkyl‐6‐phenylphenylene ether)s were prepared by the oxidative polymerization of 2‐alkyl‐6‐phenylphenols. Their dielectric constants were approximately 2.5, whereas it was found that the phenyl group at the 6‐position clearly increased the Q factor of the polymer compared with poly(2,6‐dimethylphenylene ether), PPE. These values were qualitatively predicted from the polarizability and the molar volume calculated by the theoretical analysis of the unit structure at the HF/6‐31G* level.

     

Photopolymerization of Reactive Mesogens

Summary: The photopolymerization of two reactive mesogens with photopolymerizable acrylate endgroups, the methyl substituted 1,4‐phenylene‐bis{4‐[6‐(acryloyloxy)hexyloxy]benzoate} 1 and acrylic acid 6‐{4‐[6‐(6‐acryloyloxyhexyloxy)naphthalen‐2‐yl]‐phenoxy}hexyl ester 2 has been investigated using Photo‐DSC measurements. Photocrosslinking of 1 in the nematic phase at 100 °C leads to a final conversion of 87% of the acrylate groups. It is possible to perform photopolymerization with very small amounts of photoinitiator. Even with 0.001% (10 ppm) of photoinitiator, 47% of the acrylate groups polymerize within 15 min. The polymerization of the reactive mesogen 2 proceeds faster in the smectic A phase at 100 °C compared to the isotropic phase at 120 °C and leads to a higher conversion of 75%. This can be explained by an increased local concentration of the acrylate groups between the layers of the smectic cores.

Photopolymerization of reactive mesogens.     

Syntheses and Specific Interactions of Poly(ε‐caprolactone)‐block‐poly(vinyl phenol) Copolymers Obtained via a Combination of Ring‐Opening and Atom‐Transfer Radical Polymerizations

Summary: A series of PCL‐b‐PVPh diblock copolymers were prepared through combinations of ring‐opening and atom‐transfer radical polymerizations of ε‐caprolactone and 4‐acetoxystyrene, and subsequent selective hydrolysis of the acetyl protective group. This PCL‐b‐PVPh diblock copolymer shows a single glass transition temperature over the entire composition range, indicating that this copolymer is able to form a miscible amorphous phase due to the formation of intermolecular hydrogen bonding between the hydroxyl of PVPh and the carbonyl of PCL. In addition, DSC analyses also indicated that the PCL‐b‐PVPh diblock copolymers have higher glass transition temperatures than their corresponding PCL/PVPh blends. FT‐IR was used to study the hydrogen‐bonding interaction between the PVPh hydroxyl group and the PCL carbonyl group at various compositions.

FT‐IR spectra in the 1 680–1 780 cm^?1 for PCL‐b‐PVPh copolymers with various PVPh contents.     

Pyrene Containing Polymers for the Non‐Covalent Functionalization of Carbon Nanotubes

Pyrene containing diblock copolymers based on poly(methyl methacrylate) were synthesized and investigated regarding their adsorption on carbon nanotubes (CNT). The pyrene units were introduced using a reactive ester monomer for the build up of the second block which later on was reacted polymer‐analogously with amine functionalized pyrene derivatives. As we started from the same reactive ester intermediate, full block length identity is given. We varied the length of the anchor block to find an optimal block length and used pyren‐1‐yl‐methylamine as well as 4‐pyren‐1‐yl‐butylamine as anchor units. For both anchor units a maximal adsorption was found for 13 and 20 anchor units, respectively. The absolute adsorption was best for the 4‐pyren‐1‐yl‐butylamine anchor units as the longer spacer enhances the mobility of the anchor unit. The dispersion diagram of CNTs and diblock copolymer in terms of dispersion stability was investigated and a stable dispersion of 2.5 mg · ml^?1 CNTs in THF was found.

     

A Poly(vinyl alcohol)‐graft‐Copolyester: Synthesis of a Novel Graft Copolymer Containing Adamantane Moieties as Guest for Cyclodextrin

A novel graft copolymer is synthesized from commercially available poly(vinyl alcohol) using ring‐opening polymerization. For the polymerization reaction of novel brush‐like poly(vinyl alcohol)‐graft‐poly(?‐caprolactone‐co‐(3‐/7‐(prop‐2‐ynyl)oxepan‐2‐one) 5 Sn(Oct)₂ is used as a catalyst. The formation of the graft copolymer is confirmed by ¹H NMR, ¹³C NMR, and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the modification of the novel synthesized graft copolymer via a “click” reaction to implement adamantane groups is described. The success of the “click” reaction is proven by ¹H NMR spectroscopy and visualized by decomplexation of cyclodextrin with included phenolphthalein.

     

Pyrene End‐Labeled Diblock Glycopolymers: Synthesis and Aggregation

Summary: A pyrene end‐labeled amphiphilic block copolymer, poly(ε‐caprolactone)‐block‐poly[6‐O‐(4‐vinylbenzyl)‐D ‐galactose] (Py‐PCL‐b‐PVBG), was synthesized by a four‐step method. The aggregation behavior of the diblock copolymer in solution was studied by monitoring the fluorescence of pyrene. TEM measurements revealed that the aggregates obtained by first dissolving the copolymer in N,N‐dimethylformamide (DMF), followed by the addition of water, were primarily spheres with the PCL blocks in the core. The PVBG corona was then crosslinked with glutaraldehyde. Final removal of the PCL core was accomplished by degradation under basic conditions, which resulted in the formation of hollow glycopolymer nanospheres.

Structure of poly(ε‐caprolactone)‐block‐poly[6‐O‐(4‐vinylbenzyl)‐D ‐galactose].     

Cover Picture: Macromol. Chem. Phys. 19/2005

Summary: Copolymerizations of ethylene and disubstituted diallylsilanes (CH₂CH CH₂ )₂R₂Si (R = CH₃, C₆H₅) have been investigated with various zirconocene catalysts using methylaluminoxane as a cocatalyst. The bridged stereospecific catalysts showed a higher reactivity for disubstituted diallylsilanes than the non‐bridged aspecific catalysts. Disubstituted diallylsilanes were incorporated into the polymer chain via cyclization insertion preferentially, and formed 3,5‐disubstituted silacyclohexane units in the polyethylene main chain. A zirconocene catalyst, dimethylsilylenebis(indenyl)zirconium dichloride, produced a copolymer containing pendant allyl groups derived from the 1,2‐insertion of diallyldiphenylsilane without cyclization.

     

Synthesis,Characterization, and Thermal Properties of Block Copolymers Containing Poly(styrene‐co‐4‐vinylpyridine) and Poly(styrene‐co‐butyl acrylate) by Controlled Radical Polymerization

Radical polymerization of styrene and mixtures of styrene and 4‐vinylpyridine was performed in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) producing polymers with controlled molecular weights and molecular weight distributions. The living nature of these polymers was confirmed by using them as macroinitiators in the block copolymerization of styrene and butyl acrylate. The thermal properties of the synthesized statistical diblock copolymers measured by differential scanning calorimetry indicated that a phase‐separated morphology was exhibited in most of the block copolymers. The results were confirmed by transmission electron microscopy (TEM) and small angle X‐ray scattering (SAXS) showing microphase‐separated morphology as is known for homo A‐B diblock polymers.

SAXS of a block copolymer synthesized from S/V 70:30 macroinitiators (03) with one detected T_g.     

Synthesis and Characterization of Conducting Copolymers of (S)‐2‐Methylbutyl‐2‐(3‐thienyl)acetate with Pyrrole and Thiophene

Polymerization of methylbutyl‐2‐(3‐thienyl)acetate (MBTA) was achieved by constant current electrolysis at low temperature. Subsequently, the syntheses of block copolymers of polyMBTA were accomplished in the presence of either pyrrole or thiophene by constant potential electrolysis. Moreover, the copolymer of MBTA with thiophene was obtained with constant potential electrolysis.

The synthesis of monomer MBTA.     

Novel Alternating Dioctyloxyphenylene Vinylene‐Benzothiadiazole Copolymer: Synthesis and Photovoltaic Performance

Summary: A novel alternating conjugated copolymer (poly[(dioctyloxyphenylene vinylene)‐alt‐(2,1,3‐benzothiadiazole)], C8‐PPV‐BT) consisting of electron‐rich dioctyloxybenzene and electron‐deficient 2,1,3‐benzothiadiazole repeat units was synthesized via a Pd‐catalyzed Heck cross‐coupling polycondensation. The thermal, electrochemical, optical properties, and photophysics of C8‐PPV‐BT blended with [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) have been investigated. Photovoltaic devices of ITO/PEDOT‐PSS/C8‐PPV‐BT + PCBM (1/4, w/w)/Ba/Al were fabricated and their photovoltaic parameters were measured. The results showed the energy conversion efficiency (η_e) and external quantum efficiency (EQE) were 0.335 and 11.7% (451 nm), respectively, under simulated solar light illumination having light intensity of 78.2 mW · (cm²)^?1 (AM1.5), which were both higher than those of devices based on poly[(dioctyloxyphenylene ethynylene)‐alt‐(2,1,3‐benzothiadiazole)] (C8‐PPE‐BT) and PCBM blend under the same conditions. Optical, electrochemical, and photovoltaic properties of C8‐PPV‐BT and C8‐PPE‐BT copolymers were also compared and discussed.

     

Photoinduced Polymerization of Thiophene Using Iodonium Salt

Summary: Thiophene was polymerized by means of UV irradiation using diphenyliodonium hexafluorophosphate as a photoinitiator. An initiation mechanism involving electron transfer from photochemically generated onium radical cations to thiophene was proposed. N‐Ethoxy‐2‐methylpyridinium hexafluorophosphate and triphenylsulfonium hexafluorophosphate were also found to be effective in facilitating the polymerization of thiophene. Polymerization is accompanied with the film formation on the surface of the reaction tube. The photochemically obtained polymers were characterized by FT‐IR, DSC, and SEM analyses and compared with those obtained by oxidative and electrochemical means. Electrical conductivities of the samples were measured by four‐probe technique.

Photograph of the polymerization mixture containing thiophene and iodonium salt in CH₂Cl₂ before (a), after 5 min of irradiation (b), and dried film (c).     

Polyester Obtained by Anionic Polymerization of Ethylketene

Aldoketenes are well known to undergo fast dimerization and trimerization even at low temperatures but have never been polymerized so far. For the first time, ethylketene, synthesized following the Staudinger procedure modified by McCarney, was polymerized anionically in THF with various initiators, at different temperatures (–40 and –78 °C), and with several monomer/initiator ratios. The resulting polymer was composed exclusively of polyester units, and the initiator did not affect the stereoregularity. Molecular weights up to 24 000 g · mol^?1 were obtained with lithium‐based initiators. Transfer reactions and the failure to make block copolymers highlighted a non‐living polymerization. T_g values around –18 °C and thermal stability up to 160 °C were measured.

     

Combination of Mechanochemical Degradation of Polymers with Controlled Free‐Radical Polymerization

The result of ultrasound on polymer solutions is the breakage of macromolecular C C‐bonds due to cavitation. The fact that termination reactions of mechanoradicals as disproportionation and combination are suppressed in the presence of radical scavengers makes the following method possible. Thus the use of nitroxides acting as chain‐terminating agents allows the creation of macroinitiators which can be used in controlled free‐radical polymerization. In this work, we investigate the mechanochemical degradation of poly(methyl methacrylate) (PMMA) in the presence of OH‐TEMPO and the application of the irradiated polymers as macroinitiators in a controlled radical polymerization. The content of OH‐TEMPO terminated chains in the degraded product is determined by a computer‐aided procedure on the basis of molecular weight distributions.

Ultrasonic degradation of PMMA, decrease of molar mass (M _n), and polydispersity (Pd) as a function of irradiation time, power output = 200 W, ϑ = 45–50 °C.     

Influence of Addition of Organoclays on Morphologies in Nylon 6/LLDPE Blends

Summary: Polymer blend nanocomposites containing linear low density polyethylene (LLDPE), nylon 6 and organoclays were prepared by melt mixing, and their morphologies and structures were examined with a field emission scanning electron microscope (FE‐SEM) and an X‐ray diffractometer (XRD). The size of phase‐separated domains decreased considerably with increasing content of organoclay. The d‐spacing of organoclay in the nanocomposites was increased from about 18.6 to over 28 Å. This effect was highly dependent on nylon 6 contents because nylon 6 is more polar and shows higher affinity to the organoclays compared to LLDPE.