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The self-organization and dynamics of bottlebrush polymers consisting of poly(2-bromoisobutyryloxyethyl methacrylate) (PBiBEM) backbone and grafted n-butyl acrylate (PBA) chains are studied as a function of the side-chain length by X-ray scattering, dielectric spectroscopy, and rheology in relation to the respective homopolymers. All short-range correlations are dominated by the PBA side chains, whereas long-range correlations reflect the screening of the backbones by the side chains. Such correlations show up also in the segmental dynamics. The PBA segmental dynamics are slowed-down, whereas the backbone dynamics are plasticized by the side chains. Overall the bottle-brush architecture imparts dynamic homogeneity to the backbone and side-chain dynamics.

We investigate the linear viscoelastic response of model telechelic linear and star (of varying functionality) polyisoprene melts with different molar masses above the entanglement limit in relation to their structure. We find that these systems self-assemble as a result of the strong dipolar interactions and form clusters that seem to depend primarily on the number of dipolar groups per star. The dynamics is rather complex, but some pertinent features are observed: the segmental dynamics is affected by the telechelic functionalization, especially for short arm lengths; this reflects the change of microstructure (and thus glass-transition temperature) with functionalization. The terminal relaxation is much slower compared to similar nonionic stars, reflecting the relaxation of clusters. Linear semitelechelic polymers (with only one end functionalized) aggregate in a star-like fashion. We further develop a tube model based on the time-marching algorithm for stars and linear chains, where we incorporate the association status or the chains via the dipolar interactions at each time step. The agreement of the predictions with the data, using two adjustable parameters (the average times when two dipolar pair remain associated or free, respectively), is remarkable and suggests design criteria for forming desired supramolecular assemblies.

The effect of nanoscale confinement on the dynamics of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated with dielectric spectroscopy as a function of temperature and pressure. The main effects of confinement were found in the triblocks with the more antisymmetric compositions when the radius of gyration of the confined block was comparable to the cylinder radius. It was found that the dynamics of the amorphous block accelerate upon confinement. Furthermore, confinement of the crystallizable block within cylindrical nanodomains results in the depression of the crystallization temperature.

A series of well-defined poly(methyl methacrylate)-block-poly(butyl acrylate) 3-arm star block copolymers have been synthesized by ATRP. The incorporation of polar hard segment of PMMA was made possible with the aid of halogen exchange technique. Phase-separated morphology of cylindrical PMMA domains hexagonally arranged in the pBA matrix was observed by small angle X-ray scattering in all studied materials. The mechanical and thermal properties of the PBA-PMMA 3-arm star block copolymers have been thoroughly characterized and their thermoplastic elastomer behavior was studied. It was found that the tensile properties of these materials are comparable with those of their linear ABA type block copolymer counterparts with similar compositions.

The dynamic compliances J 0 (u )a ndJ 00 (u) and the dielectric permittivities 3 0 (u) and 3 00 (u) are reported over a wide range of frequency u and temperature for comb-branched and brush-shaped poly(n-butyl acrylate) prepared by atom transfer radical polymerization. The analysis here of the viscosity h for the comb- and brush-shaped polymers indicates the need to account for an increase of the persistence length with increasing density of the side chains. Enhanced values of JS are attributed to a dilution effect arising from the side chains on the values that would otherwise arise from the backbone chain. The dielectric loss 3 00 (u) demonstrates a deviation from frequency–temperature superposition at a certain range of frequency, with the deviation increasing with increasing density of the side chains. The deviation occurs for a frequency range for which J 0 (u) and J 00 (u) are approaching their terminal response, but no corresponding deviation from frequency–temperature superposition is noted for these functions. The dielectric behavior in this region is attributed to a d-relaxation at frequencies lower than the principal a-relaxation, similar to behavior reported for certain polymers with mesogenic side chains.

Well-defined statistical, gradient and block copolymers consisting of isobornyl acrylate (IBA) and n-butyl acrylate (nBA) were synthesized via atom transfer radical polymerization (ATRP). To investigate structure–property correlation, copolymers were prepared with systematically varied molecular weights and compositions. Thermomechanical properties of synthesized materials were analyzed via differential scanning calorimetry (DSC), dynamic mechanical analyses (DMA) and small-angle X-ray scattering (SAXS). Glass transition temperature (Tg) of the resulting statistical poly(isobornyl acrylate-co-n-butyl acrylate) (P(IBA-co-nBA)) copolymers was tuned by changing the monomer feed. This way, it was possible to generate materials which can mimic thermal behavior of several homopolymers, such as poly(t-butyl acrylate) (PtBA), poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA) and poly(n-propyl acrylate) (PPA). Although statistical copolymers had the same thermal properties as their homopolymer equivalents, DMA measurements revealed that they are much softer materials. While statistical copolymers showed a single Tg, block copolymers showed two Tgs and DSC thermogram for the gradient copolymer indicated a single, but very broad, glass transition. The mechanical properties of block and gradient copolymers were compared to the statistical copolymers with the same IBA/nBA composition.

A series of well-defined poly(n-butyl acrylate)-b-polyacrylonitrile (PBA−PAN) triarm star block copolymers have been synthesized by ATRP. The incorporation of very polar hard segment of PAN was made possible with the aid of the halogen-exchange technique. Phase-separated morphology of cylindrical PAN domains hexagonally arranged in the pBA matrix was observed by atomic force microscopy and small-angle X-ray scattering in all studied materials. The mechanical and thermal properties of the PBA−PAN triarm star block copolymers have been thoroughly characterized, and their thermoplastic elastomer behavior was studied. It was found that these block copolymers retain a phase-separated morphology until temperatures of at least 250 °C. Furthermore, because of chemical cross-linking of the PAN segments that takes places at around 280 °C, the triarm star PBA-PANs preserve their elastomeric properties until temperatures of more than 300 °C.

Three recently synthesized epoxy monomers were studied. All the monomers form a nematic phase in temperatures above 80 °C. This paper presents the dielectric response of pure monomers in the frequency range of 10 6 –10 9 Hz as well as its changes occurring in the course of crosslinking with 4,4′-diaminodiphenylmethane used as curing agent. A relaxation process related to molecular motions is clearly visible in this frequency range for each of the monomers, though its characteristics are somewhat different in particular cases. The evolution of the relaxation process is visible in the course of curing. The dynamics of curing observed through dielectric data is compared with the results of differential scanning calorimetry measurements.

The mutual miscibility of five binary ethylene/norbomene copolymers of the N(x)E(1-x)/N(y)E(1-y) type where x and y represent the norbornene content in the first and second copolymers, respectively (with x/y of 0.36/0.52, 0.36/0.56, 0.36/0.62, 0.46/0.60 and 0.46/0.66), in five different compositions was studied by rheology and differential scanning calorimetry. Most of the blends do not obey the principle of time-temperature superposition, i.e., they can be considered as thermorheologically complex, and hence immiscible. The experimental data from rheology were compared to a recent lattice cluster theory. The theoretical miscibility diagram correctly predicts the experimental cases for most blend compositions except for the very asymmetric compositions. (c) 2007 Elsevier Ltd. All rights reserved. Polymer

In this work a mechanical model of deformation of two-dimensional spherulites is proposed taking into consideration its two phase structure (amorphous and crystalline phase) as well as the internal radial correlation of orientation of crystalline elements. On the basis of the proposed model, assuming specific properties of amorphous and crystalline phases, the changes in shape and in internal orientation within the spherulites, related to a given strain, have been calculated. Using the derived relations the distribution of the intensity in low angle light scattering patterns on deformed spherulites has been obtained. Theoretical results were compared with these obtained from experimental low angle light scattering and optical microscope studies on deformed spherulites in polyoxymethylene.

The small-angle light scattering patterns for fibers with helical orientation were evaluated. The experimental results of the light scattering were obtained from two kinds of helically twisted fibers and compared with the theoretical prediction considering the refraction correction. The agreement with the theory was satisfactory.

The phase behaviour of poly(n-butyl acrylate) gels swollen in smectic-A low molar weight liquid crystals (LMWLC) was investigated, in view of the increasing importance of such systems in advanced optical devices. Polyacrylate networks were prepared by ultraviolet (UV) irradiation of reactive formulations including a monomer (n-butyl acrylate), a crosslinker (hexane diol diacrylate, HDDA) and a photoinitiator (2-hydroxy-2methyl-1-phenyl-propane-1-one). The obtained dry polymer networks were characterized by a combination of physical techniques, and immersed in an excess of smectic-A LMWLC (4-n-octyl-4 � -cyanobiphenyl (8CB) and 4-n-octyloxy-4 � -cyanobiphenyl (8OCB)), forming polymer gels. A detailed study by polarized optical microscopy (POM) allowed us to determine the swelling degree of the gels and the phase behaviour of the solvent inside the polymer matrix in a wide range of temperature. It was found that the LC inside the swollen poly(n-butyl acrylate) networks remains isotropic, even if the surrounding solvent is liquid crystalline. The uptake of LMWLC inside the network preferentially takes place between the smectic to nematic and the nematic to isotropic transition temperatures of the solvent. Phase diagrams in the concentration–temperature framework were given and discussed as a function of crosslinking degree of the polymer network and temperature, and phase behaviour of the solvent. Finally, results were critically examined and compared to the few studies found in the literature.

Nanocomposite materials composed of a PTFE copolymer core and an acrylic copolymer shell have been prepared by seeded emulsion polymerization. The effect of seed particle number and shell polymer composition on secondary particle nucleation and film formation ability of the dispersions has been studied. While TEM reveals a core-shell structure present in the particles, AFM investigation of the film shows a nearly uniform dispersion of the fluorinated seed particles in a matrix formed by the shell polymer. Rheological measurements show composite behavior of the core-shell latex films, especially at elevated temperatures, and an increase in viscosity and storage modulus when compared with the properties of the pure acrylic component. These composites exhibit a solid-like behavior at lower frequencies (in the rubbery zone) indicating the formation of a network-like structure which acts as a reinforcement for the acrylic matrix. The process takes place faster at higher temperatures, probably due to the increased mobility of the cores and a corresponding improvement of the mechanical properties is observed. The fluoropolymer-PBMA nanocomposite films also show opalescent crystal like behavior due to the existence of a refractive index gradient.

In this paper, we describe atomic force microscope (AFM) friction experiments on different polymers. The aim was to analyze the influence of the physical architecture of the polymer on the degree and mode of wear and on the wear mode. Experiments were carried out with (1) linear polystyrene (PS) and cycloolefinic copolymers of ethylene and norbornene, which are stabilized by entanglements, (2) mechanically stretched PS, (3) polyisoprene-b-polystyrene diblock copolymers, with varying composition, (4) brush polymers consisting of a poly(methyl methacrylate) (PMMA) backbone and PS side chains, (5) PMMA and PS brushes grafted from a silicon wafer, (6) plasma-polymerized PS, and (7) chemically cross-linked polycarbonate. For linear polymers, wear depends critically on the orientation of the chains with respect to the scan direction. With increasing cross-link density, wear was reduced and ripple formation was suppressed. The cross-linking density was the dominating material parameter characterizing wear.

MQ siloxane resins containing Si–H functions have been made from tetramethyldisiloxane and tetraethoxysilane. Hydrosilylations with mesogenic alkenes give low molecular weight liquid crystal MQ resins with potentially useful properties.

We addressed the structure of bottle-brush macromolecules under good solvent conditions by means of scattering techniques and computer simulations. Architectural parameters, such as backbone length, side chain length and side chain stiffness were varied systematically. A consistent description of the form factors was achieved by describing the bottle-brush polymers as flexible cylinders with internal density fluctuations. The model leads to direct conclusions about parameters, such as the brush persistence length, describing the overall shape of the bottle-brush polymers. Indirect conclusions about the side chain and backbone conformation can be drawn. Experimental results were compared to those obtained from computer simulations carried out for single bottle-brush polymers using the cooperative motion algorithm. The simulation gives direct access to the pair correlation function, allowing an independent determination of the form factor. In addition direct information about the side chain and backbone conformation can be obtained. The critical parameter for lyotropic behavior of bottle-brush polymer solutions is the ratio of brush persistence length to diameter which should be of order 10 or larger. Thus the discussion of the results is focused on the impact of the architectural parameters on the persistence of the bottle-brush polymers. Experimental results on the lyotropic behavior of a bottle-brush polymer are presented.

Brush copolymers synthesized by controlled radical polymerizations were crosslinked either covalently or physically, resulting in elastomers with an unusually low equilibrium shear modulus Ge, of order 1 kPa. Examples are given for both crosslink motifs, along with the dynamic viscoelastic properties of these materials. The results are discussed in terms of the effect of the side chains on the brush polymers, which behave in some respect as a low molecular weight diluent that cannot be leached from the sample.

Linear homopolymer melts under shear stress were studied using a Monte Carlo method in a dense system, using the cooperative motion algorithm. The simulations were performed in a plane-parallel geometry, between reflective walls, for chains up to 640 beads (entangled). Behavior of the melts under shear stress was simulated by appropriate biasing of the bead move probability. Chain dynamics was monitored during reaching the equilibrium flow in the step-shear experiment (creep) simulation, in the equilibrium flow and during melt relaxation. The results were compared with those obtained for non-flowing melt. Significant differences between step-shear and steady-state simulations were observed, while chain dynamics during recovery is almost identical with that in non-flowing melt. Dynamics of the melt depended strongly on the chain length and shear stress, showing nonlinear effects for long chains. Chain orientation, coil deformation and relaxation were analyzed. Relaxation time of long chain decreased by orders of magnitude under shear following the power law. Diffusion of beads and chains was analyzed and an anomalous diffusion was observed, also in the directions perpendicular to the flow direction. In the flowing melt the effect of confined space was important, even if the wall spacing was much bigger than Rg.

Structural relaxation processes in poly(methyl-para-tolyl-siloxane) (PMpTS) polymers of three molecular weights were studied using dynamic light scattering. Two relaxation processes: the usual alpha and an additional slow one alpha' were observed and studied as function of temperature and molecular weight. Contrary to the structural relaxation, we find that in a plot T-T-g the relaxation times for the alpha', process for all molecular weights do not collapse to a single curve. For one of the samples the light scattering correlation functions were compared with the corresponding functions obtained by means of mechanical relaxation, dielectric spectroscopy and computer simulations. The simulations show that the bimodal distribution, i.e. the alpha relaxation and the slow (a') process are contained in the correlation functions of most of the probes (optical anisotropy, dipole moment, chain bond, density) in agreement with experimental observations. (c) 2006 Elsevier Ltd. All rights reserved.

Dynamic mechanical and dielectric properties of polymer–heterocycle hybrid materials were investigated. The data were analyzed within the context of complex shear modulus, G∗(ω) and the complex electric modulus, M∗(ω) formalisms. Charge transport and segmental relaxation times were derived from the electric modulus, M″(ω) and loss modulus, G″(ω), respectively. The results are discussed in terms of the effect of temperature and doping ratio onto the relaxation phenomena in these polymer–heterocycle hybrid materials.

Aromatic silicon-containing poly(amide-imide)s have been prepared by low temperature solution polycondensation reaction of various aromatic diamines having ether bridges between phenylene rings with a diacid chloride, namely bis[N-(4-chlorocarbonylphenyl) phthalimidyl]dimethylsilane. These polymers were easily soluble in polar amidic solvents such as N-methylpyrrolidone,N,N-dimethylacetamide, and N,N-dimethylformamide and can be cast from solutions into thin, flexible films. They showed good thermal stability, with initial decomposition temperature being above 410°C and glass transition temperature in the range of 263–285°C. The polymer films exhibited good mechanical properties with tensile strengths in the range of 78–109 MPa, tensile modulus in the range of 1.44–1.76 GPa, and elongation at break values ranging from 11% to 24%. Electrical insulating properties of two polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature.

A general strategy for the preparation of well-defined diblock copolymers combining a random cascade-branched dendritic (i.e., hyperbranched) and a linear block has been developed. The strategy is based on a linear poly(styrene-b-butadiene) (PS-b-PB) diblock copolymer with high molecular weight PS block and short, functional 1,2-PB block, prepared by conventional anionic polymerization. The functional PB block is used for the grafting of branched AB2-type carbosilane monomers, resulting in the attachment of a hyperbranched structure to the backbone. Slow addition of the methyldi(undecenyl)silane monomers using Karstedt's catalyst permits control of the molecular weight of the hyperbranched block, resulting in high molecular weight linear-hyperbranched diblock copolymers. Molecular weights of the block copolymers ranged between 72 800 and 106 400 g/mol for Mn, and polydispersity Mw/Mn was low (typically below 1.1), as predicted by theory for slow monomer addition. Morphological studies by TEM, AFM, and S...

Thin films, in the range of tens of micrometers thickness, have been prepared by casting onto glass plates the chloroform or N-methylpyrrolidone solutions of polyimides or poly(imide-amide)s containing silicon and phenylquinoxaline units in the main chain. The polymers have been synthesized by solution polycondensation reaction of aromatic diamines having preformed phenylquinoxaline rings with bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride or with a diacid chloride resulting from the reaction of this dianhydride with p-aminobenzoic acid. The polymers were easily soluble in polar aprotic solvents and showed high thermal stability. The free-standing films exhibited good mechanical properties with tensile strengths in the range of 48–86 MPa, tensile modulus in the range of 1.25–2.22 GPa and elongation at break in the range of 3–37%. Electrical insulating properties of some polymer films were evaluated on the basis of dielectric constant and dielectric loss and their variation with frequency and temperature. The values of the dielectric constant at 10 kHz were in the range of 2.94–3.08 for polyimides and 3.89–4.49 for poly(imide-amide)s. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3062–3068, 2006

Atom transfer radical polymerization (ATRP) of two poly(ethylene oxide) (PEO) macromonomers, with different polymerization degrees (DP n ) and different end groups, was conducted in solution via the grafting through method. Selection of a PEO methacrylate with a methyl end-group (PEOMeMA, DP PEO = 23) and a PEO acrylate end-capped by a phenyl ring (PEOPhA, DP PEO = 4) for the copolymerization led to a spontaneous gradient of PEO grafts along the copolymer backbone. Such a composition was formed because of significantly different reactivities of the two PEO macromonomers. The resulting copolymer has PEOMeMA at one end of the polymer chain, gradually changing through hetero-sequences of PEOPhA at the other chain end. An increase in the initial feed ratio of PEO acrylate reduced the rate of change in the shape of the gradient. Amorphous-crystalline structure in the copolymers was demonstrated by DSC and WAXS. The mechanical measurements of copolymers consisting of an amorphous PEOPhA and crystallizable PEOMeMA segments indicated elastomeric properties in the range of a soft rubber (G' ∼ 10 4 Pa, G' » G).

Poly(ethylene glycol) methyl ether methacrylate macromonomer (PEOMA, MW = 1100 g/mol, DPPEO = 23) and octadecyl methacrylate or acrylate (ODMA, ODA) were (co)polymerized by atom transfer radical polymerization (ATRP). The one-pot copolymerization via grafting through (macromonomer method) yielded densely heterografted copolymers (DPn = 300−500). The composition of the copolymers strongly depended on the selection of comonomer pairs; i.e., two methacrylates (PEOMA/ODMA) or methacrylate/acrylate (PEOMA/ODA) led to formation of a spontaneous random or gradient copolymer, respectively. The combination of hydrophilic and hydrophobic segments in the same polymer chain caused microphase segregation. Additionally, X-ray results indicated that frustration in packing the crystallizable segments, helical PEOMA and hexagonal ODMA crystals, can direct to an amorphous fraction instead of a semicrystalline ODMA in the graft copolymer. Thermomechanical measurements showed the soft rubbery behavior of the copolymers (104 ...

A series of liquid crystalline (LC) polymers having biphenyl (–C 6 H 4 C 6 H 4 R; R=H, OC 11 H 23 , OC(O)CH(Cl)CH 2 CH 2 COOCH 2 CH 3 ) 4-methoxyphenyl benzoate (–C 6 H 4 C(O)OC 6 H 4 OCH 3 ) and cholesteryl type mesogenic moieties were synthesized. They were made from respective –Si(CH 3 ) 2 H terminated mesogens and vinyl functionalized linear and star shape branched polysiloxanes of comb-like and dendritic topologies and were analyzed using WAXS and SAXS techniques. Contrary to the well defined typical dendrimers, in which mesogenic groups are present in an outer sphere, the dendritic systems described here contain such groups also inside the dendritic core. It was found that star shape and dendritic LC structures exhibited various calamitic mesophases (SmA, N* and SmC*) depending on the type of mesogenic groups. On the contrary, the comb-like structures give rise to formation of hexagonal phase, even though they contain typical rod-like mesogenic moieties. For the series of 4-methoxyphenyl benzoate substituted polymers the thorough studies of the relationship between their liquid crystalline properties and topology of siloxane skeleton was determined. Mechanical properties of the LC materials were also studied.

This contribution reports the combined influences of odd−even effects and the specific positioning of alkoxy side chains OR1 = (OCn+10H2(n+10)+1) and OR2 = (OCnH2n+1) (with n = 6, 7, 8, 9) on the phenylene−ethynylene and phenylene−vinylene segments, respectively, on the optical properties of hybrid polymers P(n+10)/n of general repeating unit: −Ph−C⋮C−Ph−C⋮C−Ph−CHCH−Ph−CHCH−. For the polymeric materials, visual color impression varies alternatively between orange red (P16/6 and P18/8) and yellow (P17/7 and P19/9) according to the odd and even features of the alkoxy side chains, where odd or even relates to the total number of sp3-hybridized atoms within the side chains. This side chain related effect is ascribed to both absorptive and emissive behaviors of the polymers on the basis of photophysical investigations in the bulk. Almost identical thin film absorption spectra were obtained for all four materials; however, the photoluminescence of the odd polymers, P16/6 (λf = 556 nm) and P18/8 (λf = 614 nm), ...

We describe numerical simulations of fluorescence resonance energy transfer (FRET) in symmetric diblock copolymer lamellae. The model systems were generated by Monte Carlo simulation at various finite temperatures, and virtual dyes (donors (D) and acceptors (A)) were introduced at the junction points of the block copolymer chains. We examined the effect of dye dipole orientation on energy transfer by selectively choosing the dipole orientations. The coupling effect between dipole orientation and D−A distance in the calculation of extent of energy transfer was found to be significant when donors and acceptors were confined to a thin interface at a low simulation temperature. We calculated the interface thickness of the simulated diblock copolymer lamellae based on the FRET data and the Helfand−Tagami mean field theory of polymer interfaces. FRET operates over short distances and is insensitive to the waviness of the interface.

Molecular brushes with poly(dimethylsiloxane) (PDMS) side chains were prepared by atom transfer radical polymerization (ATRP) conditions via macromonomer method (grafting through). The well-defined polymers with molecular weight distribution Mw/Mn = 1.22−1.35 and with up to 350 repeating units of macromonomers with methacrylate functionality (PDMSMA, MW = 1000 g/mol, DPPDMS = 10) were formed in the presence of CuCl/Me6TREN catalyst. Similar conditions were used for copolymerization with another macromonomer, i.e. poly(ethylene glycol) methyl ether methacrylate (PEOMA, MW = 1100 g/mol, DPPEO = 23). The comparable reactivities of both methacrylates resulted in heterografted brush copolymers with random composition and with narrow molecular distribution (Mw/Mn = 1.07−1.18). The obtained molecular brushes, consisting of amorphous PDMS fraction and crystallizable PEO segments, after annealing at high temperature had properties characteristic for soft gels (G‘ ≪ 104 Pa).

The phase state of a series of poly(n-octadecyl methacrylate)-b-poly(tert-butyl acrylate)-b-poly(n-octadecyl methacrylate) (pODMA-b-ptBA-b-pODMA) triblock copolymers, synthesized through atom transfer radical polymerization, has been investigated in bulk and on surfaces using small-angle X-ray scattering and atomic force microscopy, respectively. The mean-field theory was employed to construct the bulk phase diagram. Excellent agreement was found between the bulk and surface morphologies as well as for the domain spacing (domain spacing scaled as d approximately equal to N(0.64)), suggesting that the strong polymer-polymer interactions in bulk are also the dominant interactions on surfaces.

Diluted solutions of a single, electrically charged polymer chain, its monovalent counterions and two kinds of multivalent salts are investigated. In particular, the influence of the salt concentrations and valences on the mean effective charge per monomer, total inner energy, radius of gyration and various pair correlation functions of the monomers and free ions are analysed. The calculations show that it is the four-valent and three-valent ions, oppositely charged to the monomers, that mostly occupy the space around the polymer and tremendously increase their number there compared to that in the bulk. Furthermore, reductions in the polymer size and effective charge per monomer appear, especially for increasing amount of the four-valent salt. Thus, there is an evidence for polymer conformational changes associated with the ion condensation onto the chain.

Self-organization features of poly(p-phenylene-vinylene)/poly(p-phenylene-ethynylene)s (PPV/PPE)s polymers of constitutional structure (−PhC⋮CPhC⋮CPhCHCHPhCHCH−)n and bearing two alkoxy side chains on either every one (1) or every second (2) phenylene moieties are presented. Formation of self-assembled structures on various size scales has been examined using a combination of experimental methods. Initial investigations performed for macroscopically isotropic samples by means of DSC, POM, and 2D SALS have revealed a strong dependence of the thermal behavior and related morphologies on the side chain densities. The existence of organizational features in macroscopically oriented bulk samples (extruded filaments) was also demonstrated using 2D WAXS. Self-organization of (PPV/PPE)s into biphasic structures made of spatially segregated main chain layers with the side chains filling the space between layers was postulated. The local arrangement of the macromolecular subunits was strongly dependent on the macro...

Pyrrole and 3-(3,6-dioxaheptyl)pyrrole were polymerized in the presence of an oligo(oxyethylene monomethylether) sulfonate (DP PEO =17) with ammonium peroxydisulfate as an oxidizing agent and dry chloroform as a solvent. The oligo(oxyethylene) sulfonate acted as a phase transfer agent and also became incorporated into the polymer as a counter ion. The polymers were obtained as gel-like particles that could be easily dispersed in organic solvent and could be doped with lithium triflate to enhance the ionic conductivity of the electronically conductive materials. DSC and X-ray measurements showed a glass transition (T g ) in all samples at around -40°C which is related to the dynamics of the EO segments. In addition, the system composed of polypyrrole with oligo(oxyethylene) sulfonate counter ions showed partial crystallinity and a melting transition at 34 °C. Conductivity was explored by impedance spectroscopy with regard to frequency and temperature dependence. The data could be evaluated in the coordinates of an Arrhenius plot as the sum of two Arrhenius functions in all cases. Although one Arrhenius-type function was sufficient to describe the temperature profile of the conductivity below T g , a second term needed to be added at T> T g . The absolute values of conductivity were also dependent on the level of doping with lithium triflate. These phenomena were interpreted as a contribution of ionic conductivity by the lithium ions to the electronic conductivity, which comes about from the oxidation state of the polypyrrole backbone.

The structure of a thin zone-cast film of the hexa-n-dodecyl-substituted hexa-peri-benzocoronene (HBC) has been investigated using grazing incidence X-ray diffraction. A model with an orthorhombic unit cell containing two molecules accounts well for the observations. The molecules are arranged in a "herringbone" structure resembling the packing observed for unsubstituted HBC. The molecular disk planes are oriented perpendicularly to the substrate, rotated by approximately 39 degrees about the film normal. The relatively long side chains of dodecyl were found to be in an ordered interdigitated state. The aliphatic side chains and the aromatic HBC-cores segregate to form regular vertical domains spanning the film thickness. For in-plane rocking scans a discrete orientation distribution is observed with peaks at regular angle intervals. We interpret this as a grain boundary effect induced by alkyl chain stacking faults.

The effects of the core size, the side chain length, and the number of substituents on the supramolecular organization of polycyclic aromatic hydrocarbons have been investigated by 2D wide-angle X-ray scattering experiments performed on oriented filaments prepared by extrusion. The aromatic core size of the compounds varied between the hexa-peri-hexabenzocoronene core consisting of 42 carbon atoms and the enlarged aromatic core of 132 carbon atoms, whereas the length of the side chains extended up to 20 carbon atoms per chain. It has been observed that the lateral packing characterized by the lattice constant of the 2D intercolumnar hexagonal arrangement increases with the molecular masses of the core, forming the columnar stacks, and of the side chains which fill the core periphery. A model describing the relationship between the morphological and molecular parameters for the columnar hexagonal arrangements of the discotics is suggested and indeed proven by comparison with the experimental results.

Diyne-containing poly(p-phenylene-vinylene)s, 4a-d, of general chemical structure-(Ph-C&3bond; C-C&3bond; C-Ph- CH&3bond; CH-Ph-CH&3bond; CH-)(n), obtained through polycondensation reactions of 1,4-bis(4-formyl-2,5-dioctyloxyphenyl)- buta-1,3-diyne (2) with various 2,5-dialkoxy-p-xylylenebis(diethylphosphonates), 3a-d, are the subject of this report. The polymers exhibit great disparity in their degree of polymerization, n, which might be ascribed to side-chain-related differences in reactivity of the reactive species during the polycondensation process and which led to n-dependent absorption (solution and solid state) and emission (solution) behaviors of the polymers. Polarizing optical microscopy and differential scanning calorimetry are employed to probe their thermal behavior. The structure is investigated by means of wide-angle X-ray diffraction for both isotropic and macroscopically oriented samples. Comparison of photophysical (experimental and theoretical) and electrochemical properties of the polymers with those of their yne- containing counterparts 6a-d [-(Ph-C&3bond; C-Ph-CH&3bond; CH-Ph-CH&3bond; CH-)(n)] has been carried out. Similar photophysical behavior was observed for both types of polymers despite the difference in backbone conjugation pattern. The introduction of a second yne unit in 4 lowers the HOMO and LUMO levels, thereby enhancing the electron affinity of polymers 4 compared to polymers 6. The "wider opening" introduced by the second yne unit facilitates moreover the movement of charges during the electrochemical processes leading to minimal discrepancy, Delta E-g between the optical and electrochemical band gap energies. Polymers 6, in contrast, show significant side-chain-dependent Delta E-g values. Low turn-on voltages between 2 and 3 V and maximal luminous efficiencies between 0.32 and 1.25 cd/A were obtained from LED devices of configuration ITO/PEDOT:PSS/polymer 4/Ca/Al

The thermal properties and self-organization of hexa-peri-hexabenzocoronene (HBC) derivatives with dove-tailed alkyl chains of various lengths have been investigated using polarized optical microscopy and wide-angle X-ray scattering. It is shown that the size-related increase of steric interactions among the peripheral side chains substituted to the aromatic core leads to a dramatically lowered isotropization temperature, allowing thermal processing at practical temperatures. Additionally, the introduction of ether linkages within the side chains enhances the affinity of the discotic molecules towards polar surfaces, resulting in homeotropic self-assembly when the compounds are processed from the isotropic state between two surfaces and, for the first time, as a thin film on a single surface. It is established that the degree of homeotropic order is influenced by the phase behavior, the supramolecular order in the bulk, and the surface affinity of the corresponding derivatives. These results are important for the design of photovoltaic cells based on HBC derivatives.

The self-organization of two polycyclic aromatic hydrocarbons with different aromatic core sizes, dodecylphenyl-substituted hexa-peri- hexabenzocoronene and an extended disk consisting of 96 carbon atoms 6-fold-alkyl-substituted, on the surface from solution has been investigated. Highly ordered surface layers of both materials could be obtained by the zone-casting technique, despite an apparently low self-organization in drop-cast films. The zone-cast films revealed high macroscopic uniaxial orientation of the columns with a molecular edge-on arrangement on the glass support as confirmed by polarized optical microscopy, UV-vis measurements in polarized light, high-resolution transmission electron microscopy, and X-ray diffraction. Electron diffraction indicated a high intracolumnar periodicity of the molecules, but a low intercolumnar correlation of the disks due to the increased molecular dynamics in the liquid crystalline phase.

Liquid droplets in equilibrium with vapor are simulated at solidlike surfaces using the cooperative motion algorithm (CMA). These droplets behave like real droplets, i.e., the densities of the coexistent liquid and vapor phases obey empirical relations such as rho l - rho v proportional, variant (1 - T/Tc)(1/3). Droplet evaporation was studied under various interaction conditions, i.e., nonsoluble and soluble substrates. In the last case, substrate particles migrate toward the liquid-vapor interface to minimize the droplet surface energy. This leads to the formation of a microwell surrounded by a ringlike deposit on the substrate surface. It is shown that the ring formation in the first stages of evaporation results in pinning of the droplet contact area.

Direct nonradiative energy transfer experiments are described for the lamellar structures formed in films of poly(isoprene-b-methyl methacrylate) in which individual polymers are labeled at the junction with a single dye molecule. The donor was 9-phenanthryl (9Phe), and we compare two acceptors (1-anthryl (1An) and 2-anthryl (2An)) which differ in the orientation of their transition moments with respect to the polymer backbone. Experiments on the lamellar structures formed in films of PI-9Phe-PMMA/PI-1An-PMMA and PI-9Phe-PMMA/PI-2An-PMMA provide identical values of the interface thickness (1.1 ± 0.2 nm) between the PI and PMMA domains. The fact that a common value is obtained for the two sets of experiments indicates that the orientation parameter κ2 for the energy transfer process in this rigid system makes an identical contribution to both sets of experiments. We take these results as justification for using an averaged value of the orientation parameter 〈|κ|〉2 in fitting experimental data to the underl...

We describe the results of Monte Carlo simulations, based on the cooperative motion algorithm, of the lamellar structure generated at finite temperature by a symmetric diblock copolymer. The (70 × 70 × 70) simulation box in which the polymer chains were embedded for each simulation was rotated. based on the interfce orientation, to bring the interfacial planes of the simulated structure into parallel. We found that the interface thickness, as defined by the distribution of the junction points, became narrower at lower temperature, and that the interface plane was characterized by a waviness with a maximum peak-to-valley distance of 20-30 lattice bonds, Compared with the isotropic state (T/N = ∞), chains at lower temperatures were stretched in the direction perpendicular to the interface; but only modestly compressed in the direction paralledl to the interface. Individual block chains within the lamellar domains still behave like random coils. The block copolymer molecules exhibit only a modest tendency to orient themselves with their end-to-end vector perpendicular to the plane of the lamellar interface. Considered as an ensemble average, the results we obtained are similar to those reported from small angle neutron scattering measurements for the mean conformation of the PSd blocks of symmetrical PSd-PVP diblock copolymers.

A series of telechelic OH polysulfones (PSU) were converted to atom transfer radical polymerization (ATRP) macroinitiators by reaction with 2-bromoisobutyryl bromide. Three macroinitiators with different chain lengths were extended with poly(butyl acrylate) (PBA) to form ABA triblock copolymers. The structure and dynamics of the ABA triblock copolymers with PSU central segments and various molecular weight PBA side chains were investigated by small-angle X-ray scattering and rheology. The block copolymers form micelles with a PSU core and PBA corona. The length of each block has an important effect on the structure and resulting dynamics of the copolymers. Dynamic mechanical measurements indicate three relaxation modes: (i) PBA segmental relaxation at high frequency; (ii) PBA relaxation of the corona block at intermediate frequency; (iii) an additional relaxation process related to structural rearrangement of the micelles at low frequency. The shear modulus plateau corresponding to a soft rubbery state extends over a very broad time or temperature range because of this slow additional relaxation. triblock supramolecular copolymer unit bulk Schematic illustration of the structural elements and the bulk supramolecular structure for a symmetric triblock copolymer with a stiff central segment strongly incompatible with the other constituent.

Rigid-flexible polyethers consisting of terphenyl and aliphatic segments of various lengths along their main chains and disubstituted by dendritic wedges of various generations (Go, G 1 , and G 2 ) are examined in their bulk states. Characterization of phase transitions has been performed by means of differential scanning calorimetry (DSC) and was supported by structural information obtained from small-angle light scattering (SALS) and polarized optical microscopy (POM) experiments. In order to characterize order on the molecular size scale, two-dimensional (2D) wide-angle X-ray diffraction (WAXS) experiments have been performed for macroscopically oriented samples. All results pointed out a highly ordered nature of these materials. Both monomers and polymers were characterized. In the case of polymers, structures consisting of layered backbone sheets separated by the side dendritic moieties filling the space between them were deduced. In all cases, strong effects of molecular parameters, such as main chain flexible spacer's length and sizes of substituents, on transition temperatures (odd-even effect), degree of orientation, and distances characteristic for the supramolecular structures, were observed.

Comb-like macromolecules 3-nnn consisting of poly(p-phenylene–vinylene)/poly(p-phenylene–ethynylene) polymer backbones bearing four flexible alkoxy substituents per constitutional unit are examined in their bulk states with respect to the length of the side chains attached on the phenylene ring located between the vinylene moities. Characterization of phase behaviour has been performed by means of polarized optical microscopy and differential scanning calorimetry. Structural ordering on the molecular size scale was deduced from a qualitative analysis of wide-angle X-ray scattering effects recorded for macroscopically oriented filaments using a two-dimensional detector. Macromonomer 1 was also considered. All experimental results pointed out a highly ordered self-organization of these materials with structure parameters depending on molecular details. For both macromonomer 1 and polymers 3-nnn, formation of supramolecular assemblies is detected as temperature dependent contributions of (1) spatial segregation between aromatic and aliphatic segments, (2) stacking properties of π-conjugated fragments and (3) crystallization of the alkoxy side chains.

This paper discusses static and dynamic mechanical properties of electron beam-cured mixtures made of the nematic liquid crystal (LC) E7 and either tripropyleneglycol diacrylate (TPGDA) or propoxylated glycerol triacrylate (GPTA) as monomers differing essentially by their functionnality. Dilution of the initial mixture with LC leads to a significant weakening of the film mechanical strength. Strong effects were found on Young modulus and rubbery state modulus. As the concentration of LC increases, these mechanical parameters drop significantly together with the glass transition temperature of the polymer showing a plasticizing effect. The results for the glass transition temperatures for the polymer and the LC were confirmed by thermograms obtained by differential scanning calorimetry.

Alkoxy-substituted CN-containing phenylene-vinylene-alt-phenylene-ethynylene hybrid polymers (CN-PPV-PPE), 3a, 3b, and 7a, were obtained from luminophoric dialdehydes 1 by step growth polymerization via Knoevenagel reaction as high molecular-weight materials. Corresponding CN-free polymers 3c and 7b and an ethynylene-free polymer 5 with similar side chains were synthesized for the purpose of comparison. The chemical structures of the polymers were confirmed by IR, H-1 and C-13 NMR, and elemental analysis. Thermal characterization was conducted by means of thermogravimetric analysis and differential scanning calorimetry. Morphology was investigated by means of optical microscopy and small-angle light scattering. The final morphologies are determined by the molecular characteristics (side chains volume fraction, backbone stiffness) of the studied polymers. All the CN-containing polymers 3b, 5, and 7a exhibit higher fluorescence quantum yield in solid state (50 to 60%), but lower quantum yields (12-40%) in dilute chloroform solution, in total contrast to CN-free polymers 3c, 3d, and 7b. Identical optical, E-g(opt), and electrochemical band gap energies, E- g(ec), were obtained for 3b, 3c and 3d with intrinsic self-assembly ability, whereas a discrepancy, DeltaE(g), was observed in the cases of the fully substituted polymers 5, 7a, and 7b, whose values are dependent on the level of backbone stiffness and length of the side groups combined with the presence or absence of CN units. The incorporation of CN units in 3b and 7a lowers their respective LUMO level by 220 and 350 meV compared to their corresponding CN-free counterparts 3c and 7b, suggesting an improvement of the electron-accepting strength. Polymers 3b and 7a are efficient electron acceptors suitable for photovoltaic application. The experiments indicate that 3b is a better electron acceptor when used together with M3EH-PPV, but transport properties seem to be better for 7a. With 3b, high external quantum efficiencies of up to 23%, an open circuit voltage of up to 1.52 V, and a white light energy efficiency of 0.65% could be realized in bilayer solar cell devices. LED-devices of configuration ITO/PEDOT:PSS/polymer/Ca/Al from 3b, 3c, 7a, and 7b showed low turn-on voltages between 2 and 2.5 V. The CN-free polymers 3c and 7b exhibit far better EL parameters than their corresponding CN containing counterparts 3b and 7a

A series of novel poly(imino ketone)s (PIK) have been synthesized via palladium-catalyzed polycondensation (Hartwig−Buchwald reaction) of aromatic dichloro or dibromo ketones with various aromatic ...

Linear flexible polymers of Ng monomers, end-grafted at the density σ onto a spherical surface of radius R (“hairy sphere”), including the case of a flat impenetrable wall (R → ∞), are simulated us...

The thermal and dynamic mechanical behaviour of calcium containing co-polyurethanes namely calcium containing poly(urethane-ether)s, poly(urethane-ester)s and poly(urethane-ether-ester)s along with their control co-polyurethanes were studied. The data obtained revealed that the initial decomposition temperature of the calcium containing polymers decreases with increase in calcium content, while the control polymers showed slightly higher IDT than calcium containing polymers. The T g value of the polymers increases with increase in calcium content and decreases with increase in soft segment content and length. A single T g is observed for the calcium containing poly(urethane-ether)s based on PEG 200 and calcium containing poly(urethane-ether-ester)s based on HTPDGP 356 for various composition of Ca(HBP) 2 :PEG 200 or HTPDGP 356 :diisocyanate, indicating phase mixing of the soft segment with the ionic species and the hard segment which showed a homogenous phase. In contrast, two T g s for the calcium containing poly(urethane-ether)s based on PEG 400 and calcium containing poly(urethane-ester)s based on HTPBG 1000 for various compositions of Ca(HBP) 2 :PEG 400 or HTPBG 1000 :diisocyanate (HMDI or TDI) show the presence of a heterogeneous phase. The dynamic mechanical analysis of the calcium containing polymers based on HMDI show that with increase in the ionic content of polymer, modulus ( g ′ and g ″) increases at any given temperature. The polymers without calcium show lower modulus at any given temperature.