Lamellar Polymer Research Articles

Directed Assembly of Quantum Dots Using Brush Block Copolymers for Well-Ordered Nonlinear Optical Nanocomposites

We report the directed assembly of quantum dots (QDs) within well-ordered photonic nanocomposites using a family of (polynorbornene-graft-poly(styrene))-block-(polynorbornene-graft-poly(ethylene oxide)) (PS-b-PEO) brush block copolymers (BBCPs). Cadmium selenide (CdSe) nanoparticles (NPs) modified with 11-mercaptoundecylhydroquinone are selectively incorporated within the PEO domains of the self-assembled BBCPs via strong hydrogen-bonding interactions between the ligands on QDs and PEO brushes of the BBCPs. Well-ordered QD arrays were readily created within a periodic lamellar polymer matrix, or one-dimensional photonic crystal, with a widely tunable lattice spacing ranging from 46.2 to up to 145 nm. The loading concentration of the QDs can be up to 30 wt % (15 vol %) while maintaining a well-ordered lamellar morphology, providing an optical gain material platform for the systematic investigation of optical properties. Strong photoluminescence and third harmonic generation from the well-ordered QD arrays were observed via multiphoton excitation using femtosecond (fs) laser light at several optical wavelengths from 700 to 1550 nm.

Assembling semiconducting molecules by covalent attachment to a lamellar crystalline polymer substrate.

We have investigated the potential of polymers containing precisely spaced side-branches for thin film applications, particularly in the context of organic electronics. Upon crystallization, the side-branches were excluded from the crystalline core of a lamellar crystal. Thus, the surfaces of these crystals were covered by side-branches. By using carboxyl groups as side-branches, which allow for chemical reactions, we could functionalize the crystal with semiconducting molecules. Here, we compare properties of crystals differing in size: small nanocrystals and large single crystals. By assembling nanocrystals on a Langmuir trough, large areas could be covered by monolayers consisting of randomly arranged nanocrystals. Alternatively, we used a method based on local supersaturation to grow large area single crystals of the precisely side-branched polymer from solution. Attachment of the semiconducting molecules to the lamellar surface of large single crystals was possible, however, only after an appropriate annealing procedure. As a function of the duration of the grafting process, the morphology of the resulting layer of semiconducting molecules changed from patchy to compact.

A Highly Sensitive Luminescent Dye@MOF Composite for Probing Different Volatile Organic Compounds

The probing of volatile organic compounds (VOCs) is critical and challenging in biotechnology and environmental monitoring. Incorporation of luminescent moieties into metal-organic frameworks (MOFs) has produced many unique luminescent sensors for probing different VOCs. The emissions of most MOF sensors are based mainly on the single transitions of luminescent moieties, so the luminescence readouts are only predominant for some special VOCs. We use a natural amino acid derivative as the luminescent moiety to result in a lamellar coordination polymer, and further embed luminescent dye molecules in the crystal matrix to result in a luminescent dye@MOF sensor. The composite sensor exhibits excellent sensitivity for decoding different VOCs with clearly differentiable fluorescence emission by tuning the energy transfer efficiency from the organic ligand to the dye moieties. The composite luminescent sensor is self-calibrated, and much more stable and instantaneous than other more widely explored luminescent sensors.

Stabilization of Nuclei of Lamellar Polymer Crystals: Insights from a Comparison of the Hoffman–Weeks Line with the Crystallization Line

We have studied melting of poly(butylene succinate), isothermally crystallized over a wide temperature range, employing a combination of the Hoffman–Weeks plot and the Gibbs–Thomson crystallization line, determined by small-angle X-ray scattering measurements. A change in the slope α of the Hoffman–Weeks (H–W) line, accompanied by a change of the slope of the crystallization line, was observed for crystallization temperatures higher than 110 °C. α was reaching a value of 1, implying that no intersection point between the H–W line and the Tm = Tc line could be obtained. (Tm is the measured melting temperature and Tc is the temperature at which the sample was crystallized). This observation was corroborated by the crystallization line, which was found to be parallel to the melting line for Tc > 110 °C. We relate these changes in slope to different stabilization mechanisms of the secondary nuclei at the growth front of polymer lamellar crystals. For Tc > 110 °C, secondary nuclei are proposed to be stabilized...

Phase densities and lamellar morphologies of semicrystalline polyethylenesviaabsolute small-angle X-ray scattering measurements

With the crystalline volume fraction from small-angle X-ray scattering (SAXS) and the density of the crystalline phase from wide-angle X-ray diffraction, the amorphous phase density of two representative polyethylenes was calculated as a function of temperature using the absolute total SAXS scattering power or invariant. The density of the amorphous phase in semicrystalline polyethylene is crystallinity independent and is lower than melt-extrapolated values reported in the literature. Model-independent SAXS-based crystallinity values can be calculated with the aid of the densities of the crystalline and amorphous phase and the absolute SAXS invariant. Such model-independent crystallinity values can be used in SAXS curve-shape analysis procedures to obtain the average thickness of the crystalline and amorphous layers also in the case of non-ideal lamellar semicrystalline polymer morphologies for which the number-average long period cannot be retrieved from the maxima in correlation functions or interface distribution functions.

EFFECTIVENESS RESEARCH ON A WAVY LAMELLAR PLATE-TYPE BIOFILTER WITH A CAPILLARY SYSTEM FOR THE HUMIDIFICATION OF THE PACKING MATERIAL APPLYING INTROINDUCED MICROORGANISMS

To conduct research, a new generation plate-type air treatment biofilter for removing gaseous pollutants from air has been applied under laboratory conditions. A distinguishing feature of the packing material of the biofilter includes wavy lamellar polymer plates placed to each other and producing a capillary effect of humidification. While having such an arrangement, wavy lamellar plates also have rather wide spacing (6 mm), and therefore the employment of the structure of the plate-type packing material decreases the aerodynamic resistance of the device. A wavy porous plate is made of a polymer plate that ensures stiffness. Both sides of the wavy lamellar polymer plate have attached steam exploded birch fiber pellets under which, to increase plate capillarity, not-woven caulking material is put. This technological decision allows effectively enhancing the durability of the biopacking material. The work presents the results of research on the efficiency of the biodestruction process of acetone, xylene and ammonia. With reference to the conducted investigation, the high efficiency of air treatment and microbiological activity has been established. When pollutant gases (acetone, xylene and ammonia), under a velocity of 0.08 m s–1, passed through the biopacking material, microbiological activity in the material reached on average 1×108 cfu/cm2, and air treatment efficiency made 90.7%.

Combining fast-scan chip-calorimeter with molecular simulations to investigate superheating behaviors of lamellar polymer crystals

We studied the power-law heating-rate dependence of superheating for the melting of alpha- and beta-crystals of isotactic polypropylene by means of chip-calorimeter, and expanded our parallel observation to higher heating rates by means of molecular simulations. We observed that, at low heating rates, the melting of lamellar crystals after thickened via melting-recrystallization exhibits no power-law-dependent superheating; at medium heating rates, the melting of crystals after thickened via chain-sliding diffusion exhibits the power-law-dependent superheating with the power indexes sensitive to chain mobility in the crystals; while at high heating rates, the zero-entropy-production melting of crystals without further thickening maintains the power-law-dependent superheating but with the power indexes uniform at an upper-limit 0.375. We attributed the index 0.375 to a result combining local intramolecular nucleation and global roughening growth at the lateral surface of lamellar crystals, which dominate the kinetics of crystal growth and melting of polymer crystals at high temperatures.

Combining TMDSC measurements between chip-calorimeter and molecular simulation to study reversible melting of polymer crystals

Reversible melting is a phenomenon unique to polymer crystals, which raises an excess reversing heat capacity near their melting points. By means of temperature-modulated differential scanning calorimetry (TMDSC) measurements with an expanded frequency range in chip-calorimeter, we studied reversing heat capacities of alpha- and beta-form crystals of isotactic polypropylene. We attributed their differences at high temperatures and low frequencies to variable chain mobility in these two crystals. We further performed parallel dynamic Monte Carlo simulations of lattice polymers with variable chain mobility in the crystals to confirm this attribution. Our observations provide the first evidence on the role of chain mobility in the microscopic mechanism of reversible melting at the fold-end surfaces of lamellar polymer crystals.

Crystal Chemistry of Uranyl Carboxylate Coordination Networks Obtained in the Presence of Organic Amine Molecules

AbstractThree uranyl isophthalates (1,3‐bdc) and two uranyl pyromellitates (btec) of coordination‐polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine‐based molecules [1,3‐diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N‐dimethylformamide]. (UO2)2(OH)2(H2O)(1,3‐bdc)·H2O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H2O molecules. The compounds (UO2)1.5(H2O)(1,3‐bdc)2·0.5H2dap·1.5H2O (2) and UO2(1,3‐bdc)1.5·0.5H2dap·2H2O (3) consist of discrete uranyl‐centered hexagonal bipyramids connected to each other by a ditopic linker to form a single‐layer network for 2 or a double‐layer network for 3. The protonated diamine molecules are located between the uranyl–organic sheets and balance the negative charge of the layered sub‐networks. The phase (UO2)2O(btec)·2Hdma·H2O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO2(btec)·2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non‐bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen‐bond network. The different illustrations show the structural diversity of uranyl–organic coordination polymers with organic amine molecules as countercations.

Layered structures and nanosheets of pyrimidinethiolate coordination polymers

We report the synthesis, crystal structure and exfoliation of a new member of an important family of layered compounds: lamellar pyrimidinethiolate coordination polymers. Conductivity measurements and DFT calculations of iron(II) pyrimidine-2-thiolate show that this material and a related compound are insulators.

Insight into the Structure and Nanoscale Conductivity of Fluorinated Ionomer Membranes

A material-sensitive atomic force microscopic (AFM) tapping mode was combined with current measurements to investigate structure, phase separation, and conductive structure of surfaces and cross sections of long side chain Nafion and short side chain AQUIVION PFSA ionomer membranes. We found unexpected large-scale ordered structures consistent with a dominant lamellar polymer structure at the cross sections. The highly terraced areas of both ionomers have a wide distribution of layer thicknesses from sub-nanometer to a few nanometers. In both broad size distributions, preferential sizes were identified that reflect the different lengths of the molecular side chains, indicating a stacking in layers. The nanoscale phase separation of the ionomer was analyzed by using the capacitive current distribution. In AQUIVION PFSA, larger connected water-rich ionic areas were found than in Nafion with same total ionic area. A steady-state current at the cross sections evolved only after an activation period by enforcing current flow though the membrane. A comprehensive and heterogeneous current distribution was observed with highly conductive areas. In contrast, on outer membrane surfaces, only non-continuous spot-like currents were observed. In general, our measurements are consistent with conduction in water layers in-between polymer chains and a bi-continuous structure under faradaic current flow.

Preparation of a solution‐processable, nanostructured ionic polyacetylene

ABSTRACTPolymerization of a self‐assembled 1‐dodecyl‐3‐propargylimidazolium bromide ionic liquid (IL) yields a nanostructured ionic polyacetylene. A 1:1 aqueous mixture of the amphiphilic IL produces an ordered lyotropic mesophase that adopts a hexagonal perforated lamellar structure. Rh (I)‐mediated polymerization of the assembled mixture yields a hexagonal modulated lamellar structured polymer. FTIR spectroscopy reveals that the polymer was self n‐doped. The polymer was fractioned into three components with the majority product, possessing an intermediate molecular weight that is soluble in polar organic solvents. In methanol, the optical band gap of the main fraction was determined to be 2.38 eV and was nonemissive. The solution‐processable polymer was airbrush sprayed onto glass substrates to give a liquid‐crystalline, lamellar structured semiconductive film (7.02 × 10−5 S cm−1). The polymer resisted oxidation (degradation) upon storage in air as monitored by vibrational spectroscopy. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1215–1227

Systematic Kinetic Analysis on Monolayer Lamellar Crystal Thickening via Chain-Sliding Diffusion of Polymers

Lamellar polymer crystals are metastable due to their limited lamellar thickness. We performed dynamic Monte Carlo simulations of lattice linear polymers to investigate the kinetics of isothermal thickening via chain-sliding diffusion in single lamellar crystals of polyethylene and poly(ethylene oxide). We sorted out three typical cases for controversial experimental observations. The basic case is a continuous increase of lamellar thickness for heavily folded long chains, with a logarithmic time dependence typical at the lateral growth front. Its kinetics is dominated by the activation energy barrier for sliding diffusion with higher speeds at higher temperatures. For integer-folded short chains, however, the lamellar thickness increases discontinuously, and its kinetics is dominated by a free energy barrier for surface nucleation. The latter can be further split into two cases: the thickening in the melt is mainly driven by the bulk free energy, with lower speeds at higher temperatures due to a temperature-sensitive barrier; while the thickening on a solid substrate is mainly driven by the surface free energy, with higher speeds at higher temperatures due to a temperature-insensitive barrier. The simulations facilitate our systematic understanding to the case-by-case microscopic mechanisms for the thickening of monolayer lamellar crystals via sliding diffusion of polymers.

Influence of Tie and Loop Molecules on the Mechanical Properties of Lamellar Block Copolymers

We use coarse-grained molecular dynamics simulation to study the influence of molecular architecture and conformations on the mechanical response of lamellar nanostructured polymers. For this purpose, a recently developed generation method (radical like polymerization method) has been optimized to generate lamellar triblock copolymer samples with alternate glassy and rubbery stacks. Several systems, with various rate of loop (both ends of the chain are in the same glassy block), cilia (cut triblock, effectively a diblock chain) and tie molecules (TMs) (chain that bridges two subsequent glassy blocks through the intermediate rubbery block) were generated. Uniaxial tensile tests were performed, the tensile strain being applied in the normal direction of the lamellae. This situation can be understood as a simple way of mimicking the deformation of the equatorial stack in semicrystalline polymers, with the “hard” phase being the glassy (rather than crystalline) one. The resulting constitutive laws reveal the ...

Growth Rates of Edge-on Lamellar Crystals Confined in Polymer Thin Films

The growth rates of edge-on lamellar polymer crystals in variable thickness films were investigated in terms of dynamic Monte Carlo (MC) simulations. The growth rates linearly decreased with decreasing film thickness for the thinner films and were nearly constant for the thicker films. The mean stem lengths (crystal thickness) were also constant in different thickness films. The crystal widths parallel to the film thickness increased more slowly with increasing film thickness in the thinner films than that in the thicker films, indicating they were restrained by the film thickness. We propose that the growth rate of edge-on lamellar crystals in thin films is dominanted by the crystal width in the thinner films and by the crystal thickness in the thicker films; the variation of the film thickness can change the three-dimensional shape of the crystal growth front, also affecting the growth rate of the edge-on lamellar crystal.

Crystallization Kinetics of Lamellar Crystals Confined in Polymer Thin Films

We used dynamic Monte Carlo simulations to investigate the crystallization kinetics of flat-on lamellar polymer crystals in variable thickness films. We found that the growth rates linearly reduced with decreasing film thickness for the films thinner than a transition thickness dt , while they were constant for the films thicker than dt . Moreover, the mean stem lengths (crystal thickness) we calculated decreased with film thickness in a similar way to the growth rates, and the intramolecular crystallinities we calculated confirmed the film thickness dependence of the crytsal thickness. Besides, the crystal melting rates in thin films were calculated and increased with decreasing film thickness. We proposed a new interpretation on the film thickness dependence of the crystal growth rate in thin films, suggesting that it is dominated by the crystal thickness in terms of the driving force term (l–l min) expressed by Sadler, rather than the chain mobility based on experiments. The crystal thickness can determine whether a crystal grows or melts in a thin film at a fixed temperature, indicating the reversibility between the crystal growth and melting.

Evolution of entanglements during the response to a uniaxial deformation of lamellar triblock copolymers and polymer glasses

Using coarse-grained molecular-dynamics simulations, a generic styrene-block-butadiene-block-styrene triblock copolymer under lamellar conformation is used in order to investigate the mutual entanglement evolution when a structure of alternating glassy (S)/rubbery (B) layers is submitted to an imposed deformation. By varying the amount of loop chains between each phase, i.e., noncrossing chains, it is possible to generate different types of S/B interface definitions. A specific boundary driven tensile strain protocol has been developed in order to mimic "real" experiments and measure the stress-strain curve. The same protocol is also applied to a reference state consisting in a directed glassy homopolymers, as well as to an isotropic glassy polymer. The evolution of initial mutual entanglements from the undeformed samples during the whole deformation process is monitored. It is shown for all considered systems that initial entanglements mostly participate to the preyield regime of the stress-strain curve and that this network is debonded during the strain-hardening regime. For triblocks with a non-null amount of crossing chains, the lower the amount is, the longer the memory effect of the initial entanglement network in the postyield regime is. On the fly distributions of entanglements, which depart from the postyield regime, depict memory effects and long-time correlations during the strain-hardening regime. For triblocks, loop chains reinforce these effects.

Studies on one 2D cadmium(II) coordination polymer and two mononuclear cadmium(II) complexes with trans or cis configuration having 3-bromo, 3,6-dibromo, and 3,8-dibromo 1,10-phenanthroline ligands

Three novel Cd(II) complexes, formulated as [Cd(3,8-dibromo-1,10 -phen- κ 2N , N′)( l-tar)] n ( 1), trans-[Cd(3,8-dibromo-1,10 -phen- κ 2N , N′) 2(NO 3- κ 2O , O′) 2]·(CH 3CN) ( 2) and cis-[Cd(3,6-dibromo-1,10-phen- κ 2N , N′)(3-bromo-1,10-phen- κ 2N , N′)(NO 3- 2 O, O′)(CH 3OH- κO)](NO 3) ( 3) (phen = phenanthroline, l-tarH 2 = l-tartaric acid), have been synthesized and characterized in this paper. In coordination polymer 1, the [Cd 2(3,8-dibromo-phen) 2] 4+ cations are bridged by l-tar ligands into an infinite 2D lamellar polymer along the c-axis, and the neighboring 2D polymers are further extended into a 3D supramolecular network by π–π stacking interactions. Complexes 2 and 3 are both mononuclear cadmium complexes but with different conformation ( trans or cis). In the crystal packing structures of 2 and 3, molecules are arranged into three-dimensional (3D) frameworks by intermolecular hydrogen bonding and π–π stacking interactions.

Direct Observation of Alkyl Chain Interdigitation in Conjugated Polyquarterthiophene Self‐Organized on Graphite Surfaces

AbstractA solution processible polymer—poly(3,3‴‐didodecylquaterthiophene) (PQT‐12) is investigated at the liquid/solid interface using the scanning tunneling microscopy (STM). Two‐dimensional ordered films made up of self‐assembled domains, with dimensions of 100 nm × 50 nm adsorbed on highly oriented pyrolytic graphite (HOPG) were formed. These domains consist of parallel lamellar polymer chains, with the alkyl chains forming interdigitated structures, along with U‐shaped and closed ring segments of the polymer chains. A polymer chain packing model is proposed herein, which attempts to propose a correlation between the packing of long chains and charge mobilities. These STM results could help in understanding the relationship between the extended conjugation and molecular organization of the PQT‐12 chains.magnified image

Synthesis, Crystal Structures and Thermal Analysis of Two New Silver(I)–Dithioether Lamellar Coordination Polymers

Two new silver(I)–dithioether coordination polymers based on the self-assembly of the dithioether ligands L n −R = CH3–S(CH2) n S–CH3 (n = 1, 3) and AgX silver salts, where X = ClO4 − (1) and PF6 − (2), have been synthesized and characterized by single crystal X-ray diffraction and TGA. The crystallographic data of those complexes are: (1) Monoclinic P21/c; a = 16.5861(3) A; b = 10.1048(2) A; c = 15.7843(3) A; β = 112.570(1)°; V = 2442.83(8) A3; Z = 4. (2) Monoclinic P21/n; a = 8.6500(2) A; b = 9.4053(2) A; c = 24.0357(6) A; β = 92.750(2)°; V = 1953.19(8) A3; Z = 4. In both complexes, the dithioether building blocks propagated the silver(I) centers to build cationic lamellar coordination polymers, while ClO4 − and PF6 −, which were sandwiched between silver-ligand sheets, counterbalance only the charge of the networks. The thermogravimetric investigation reveals that those complexes decompose in a single step respectively to metallic silver and silver salt. Two new silver(I)–dithioether coordination polymers, obtained from the self-assembly of dithioether ligands and AgX salts with noncoordinating counteranions (X = ClO4 − and PF6 −), were characterized by X-ray crystallography and thermogravimetric analysis (TGA).