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The construction of heterocyclic aramid nanofibers (HNFs) was reported for the first time in this study by a polymerization-induced self-assembly method. 2-(4-Aminophenyl)-5-aminobenzimidazole was introduced as the third monomer to participate in the polymerization of poly(p-phenylene terephthalamide) and HNFs were successfully prepared based on the balance of the solvent isolation effect and intermolecular interaction. Subsequently, HNFs were fabricated into nanopaper, which has uniform micro–nano structures and significantly improved mechanical properties and electrical insulation.

The mechanical properties of poly(arylene sulfide sulfone) (PASS) electrospun membrane were significantly enhanced by co-electrospinning with semi-aromatic nylon poly(m-xylene adipamide) (MXD6), another engineering plastic with high thermal stability and good mechanical properties. The tensile strength of PASS membrane increased with increased incorporation of MXD6, and was tripled when 20% MXD6 was incorporated. The mechanism of the mechanical property improvement is the existence of hydrogen bonding interaction between PASS and MXD6 and between adjacent fibers at the intersections. Thermal properties of the PASS/MXD6 membranes were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), which showed that the membranes could be stably utilized up to 180 °C without any change in appearance and without decomposition. Contact angle measurements of all the membranes showed hydrophobic character. To demonstrate the potential applications of PASS/MXD6 blend membranes, their oil absorption capacities were evaluated with three oils of different viscosities, which proved that the PASS/MXD6 membranes are better absorbents than commercial non-woven polypropylene fibers. Therefore, PASS/MXD6 fibrous membranes produced by electrospinning have a great potential in practical applications.

The manipulation of nanobuilding blocks into a 3D macroscopic monolith with ordered hierarchical structures has been much desired for broad and large-scale practical applications of nanoarchitectures. In this paper, we demonstrate a fully bottom-up strategy for the preparation of aramid aerogel monoliths. The process starts from the synthesis of poly(p-phenylene terephthalamide) (PPTA) through the polycondensation of p-phenylenediamine and terephthaloyl chloride, with the assistance of a nonreactive dispersing agent (polyethylene glycol dimethyl ether), which helps the dispersal of the as-synthesized PPTA in an aqueous medium for the formation of p-aramid nanofibers (ANF). Then the vacuum-assisted self-assembly (Vas) technique is skillfully connected with the ice-templated directional solidification (I) technique, and the combined VasI method successfully tailors the self-assembly of ANF to transform the 1D nanofibers into a 3D aerogel monolith with a specific long-range aligned, lasagna-like, multilaminated internal structure. The study of the aerogel microstructure revealed the dependence of the lamina orientation on the direction of the freezing front of ice crystals. This direction should be parallel to the deposition plane of the Vas process if a long-range aligned lamellar structure is desired. The anisotropy of the multilaminated aerogel was proven by the different results in the radial and axial directions in the compression and thermal conductivity tests. As a kind of organic aerogel, the ANF monolith has typical low density, high porosity, and low thermal conductivity. Additionally, the ANF monolith exhibits high compressive stress and excellent thermal stability. Considering its high performance and facile preparation process, potential applications of the ANF aerogel monolith can be expected.

Aerogel has been widely known as a low-density and highly porous material and is closely connected with the complex processing methods, such as freeze-drying or supercritical drying. In this work, using the polymerization-induced aramid nanofiber (PANF) as a building block, we put forward a modified freezing-drying method for the high-efficiency preparation of all-para-aromatic-amide aerogels. In the preparation process, PANF hydrogel is first frozen at -18 °C and then dried at 20-150 °C for the formation of PANF aerogel. The PANF framework formed during the freezing process is crucial for the formation of the PANF aerogel. Moreover, the space-occupying effect of ice crystals is also helpful for the formation of the macroscopic pore structure in the aerogel. Aerogels with large size or well-controlled shape could be successfully obtained by this method. Through the variation of PANF concentration in the hydrogel and drying temperature, aerogels with different densities (20-185 mg/cm3) could be achieved, and the lowest density is reached at 150 °C, with the PANF concentration of 0.7%. The low-density PANF aerogels show high specific compressive strengths and low thermal conductivities, which are comparable to those resulting from the freeze-drying or supercritical drying method. Furthermore, the shrinkage phenomenon in the drying process could be skillfully utilized for the preparation of PANF aerogel-coated objects. The PANF aerogels could be applied as a thermal insulating material or shock absorption material in practical applications.

Proper building of polymer/polysilsequioxane composite is determined by deep-rooted structural variables. This work focuses on the fabrication of silane-grafted waterborne polyurethane (DWPU)/polyphenylsilsequioxanes (PPSQ) composites by blending and in-situ methods, respectively. By using blending method, PPSQ nanoparticle latexes were dispersed in DWPU. By using in-situ method, as the precursor of PPSQ, phenyltrimethoxysilane was mixed in DWPU, and PPSQ was expected to be generated via in-situ sol-gel reaction during film formation. We systematically investigated the influences of PPSQ and its incorporation method on the phase separation of films. The competition between a heterophase-triggered phase separation and a silane-based crosslinking was found during film formation. The intrinsically local ordering permutation of PU segments was interrupted more or less with PPSQ. Both surface composition and morphology were altered in correspondence to the different addition amount of PPSQ. Furthermore, optical, mechanical, and thermal resistances of composite films were also investigated for potential applications as coatings.

The recent researches on waterborne polyurethane (WPU) have been much highlighted to fulfill the both requirements of environment and material performance. Herein, a simple copolymerization approach is demonstrated toward the tough, fluorescent and adhesive WPU elastomer films by the incorporation of para aromatic amide (aramid)-urea segments in the backbone of the polymer. The synthesis of the poly(amide-urea-urethane) was carried out through two steps of chain extension reactions, and the aramid motif, 4,4'-diaminobenzanilide (DABA) was used as the chain extender in the second step of chain extension before the polymer was neutralized and dispersed in water. The aramid-urea segments promoted the H-bonding association of the polyurethane matrix during the film formation of the WPU, which facilitated the microphase separation as well as the pronounced elevation of film performance. Under the DABA content of 4 wt%, the ultimate tensile strength increased to 73 MPa, 380% of that without DABA incorporation. Importantly, the WPU film showed remarkable toughness of 372 MJ·m-3 with the elongation at break of ~1250%. The water adsorption of the film was also suppressed to below 3% in 24 h of the water uptake test. Not only that, but the elastomer film also exhibited high adhesion to metal surfaces to withstand a hanging weight of 27.5 kg with the bonding area of 25 mm × 50 mm. Besides, the film was also able to emit bright blue fluorescence under the excitation of UV light. The combining of high strength, toughness, water resistance and photoluminescence in the WPU will provide the elastomer great potential as environmentally friendly multifunctional material.

Aramid paper based on poly (p-phenylene terephthamide) (PPTA) is a typically excellent insulation material, but the common preparation is complex and tedious. In this work, using the PPTA based aramid nanofibers (ANFs) synthesized by the bottom-up polymerization induced self-assembly process, insulation paper was fabricated through the vacuum assisted filtration without any high pressure or high temperature treatment. Importantly, the ANF paper exhibits improved electrical insulation, desired mechanical strength and good thermal stability, which is attributed to the tightly weaved architecture formed by the nanofibers.

The direct synthesis of polymer microspheres modified by aramid nanofibers (ANFs) is an interesting challenge. This work describes a simple aqueous process to prepare polystyrene (PS)/ANF composite microspheres, where the specific ANF network was "dressed" on PS. ANF was derived from the copolymerization of terephthaloyl chloride, p-phenylene diamine, and methoxypolyethylene glycol and could be dispersed in water stably. We applied the as-synthesized ANF as a Pickering emulsifier in the o/w emulsion of styrene monomer. Radical polymerization was subsequently initiated in the Pickering emulsion system. The combination of ANF with polymer spheres was revealed by scanning electron microscopy (SEM) and thermal gravity analysis. The role of ANF in the monomer emulsion as well as in the polymerization was studied through SEM, optical microscopy, optical stability analyzer, and pulse nuclear magnetic resonance combined with the polymerization kinetic analysis. Moreover, we investigated the effects of other synthesis parameters, such as monomer type, monomer content, pH value, and salt concentration.

Interfacial localization of carbon fillers in cocontinuous-structured polymer blends is well-known as a high-efficiency strategy for conductive network formation. However, a comparison with interfacial localization of carbon fillers in sea-island-structured polymer blends is lacking. Here, three types of highly efficient conductive networks formed on the basis of interfacial localization of carbon black (CB) in polyamide 6 (PA6)/poly(butylene terephthalate) (PBT) blends with different blend compositions (80/20, 50/50 and 20/80 vol/vol) were investigated and compared in terms of electrical resistivity, morphology as well as rheological and mechanical properties. The order of the electrical percolation threshold of CB in the three blends is 50/50 &lt, 20/80 &lt, 80/20, which can be attributed to different network structures. The rheological percolation thresholds are close to the electrical ones, confirming the formation of CB networks. The formation mechanisms for the three types of CB network structures are analyzed. All the three types of PA6/PBT-6 vol% CB composites showed improved tensile strength compared with PA6/PBT blends, being in favor for practical applications.

The processing of poly(p-phenylene terephthalamide) (PPTA) has long been a great challenge. This work reports a simple "monomers-nanofibers-macroscopic product" (MNM) hierarchical self-assembly approach to build 3D all-PPTA engineering materials. This approach mainly includes the preparation of polymerization-induced aramid nanofibers (PANFs) from monomers and the fabrication of all-PPTA materials from PANF hydrogel. Various 3D architectures, including simple solid bulks and sophisticated honeycombs (HCs), are obtained after the dehydration and shrinking of the PANF hydrogel. The tensile strength and compressive yield strength of PANF bulk are more than 62 and 90 MPa, respectively, which are comparable to typical engineering plastics. The compressive strength of PANF HC with a density of 360 kg m-3 is more than 24 MPa. The thermal stability of PANF bulk and PANF HC are as good as that of Kevlar fiber and almost no decomposition occurred before 500 °C in a nitrogen atmosphere. Furthermore, the MNM process is performed under mild conditions, without high temperature, high pressure, or corrosive solvent. The MNM process is a novel strategy for the processing of all aromatic polyamide materials with complex structures and high performances and would be another development since the breakthrough of liquid crystal spinning technology of PPTA.

Poly(p-phenylene terephthalamide) (PPTA) nanofibers were prepared via a polymerization induced self-assembly process with the assistance of methoxy polyethylene glycol (mPEG) for stability and dispersity. In the traditional process of the solution polycondensation of p-phenylenediamine (PPD) and terephthaloyl chloride (TPC), PPTA will aggregate and precipitate with the chain growth due to the liquid crystalline characteristic. The introduction of mPEG can control the aggregation degree of PPTA molecules and stabilize the formed aggregates, which drives the self-assembly of PPTA molecules and results in the formation of nanofibers. The obtained nanofibers specialized by the great length–diameter ratio were characterized in detail. The effects of mPEG addition on the formation and the performance of the fibers were all studied in the work. The nanofibers can disperse in variety of organic solvents and water. Moreover, the nanofibers can be deposited for the formation of thin films with excellent transparency and thermal stability, which has great potential applications such as the separator of lithium ion battery.

In this work, a novel bisbenzimidazolylpyridine-functionalized fluorescent epoxy resin was synthesized for organophosphate pesticide detection. The epoxy resin was characterized by Fourier-transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy ( 1 H NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and fluorescence spectroscopy. After loading with Eu(III) ions, the epoxy resin showed a strong fluorescence emission. The fluorescence emission was observed to be instantaneously quenched when exposed to trace amount of diethyl chlorophosphate in solution. The Stern–Volmer quenching constants K sv for quenching at 617 nm was determined to be 0.377 × 10 3 L/mol. This sensitive emission-quenching function and easy processing nature of the polymeric support enable the resin to be a promising chemosensor candidate for the detection of organophosphates.

A multiblock fluorinated polyurethane was synthesized using tetraphenylethane-based polyurethane as macroiniferter to free-radically polymerize 1H,1H,3H-trihydro perfluoro-2,4-dimethylpentyl methacrylate (FDPMA). Simultaneous self-assembly occurred in FDPMA polymerization process and various nanostructures, like multicore particles, formed depending on FDPMA concentration. Fluorophobic effect and the cooperation of the fluorinated blocks with polyurethane blocks are demonstrated to be the main contribution. That soluble FDPMA in DMF becomes insoluble after polymerization triggers the self-assembly process and leads to the nanostructure formation, and the polyurethane blocks that are soluble in DMF and immiscible with the fluorinated blocks stabilize the discrete nanostructures. Further, the nanostructures in solutions can evolve into various morphologies, such as disk and fiber, when dried to solid state. All these results not only reveal the feasibility and robustness of the multiblock copolymer on the modulation of self-assembly structure but also represent a facile and efficient approach for novel nanostructure construction. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013

Stable and uniform dispersions of para-aramid nanofibers have been prepared by adding methoxypolyethylene glycol (mPEG) in the polymerization process, followed by strong shear and dispersion. Aramid membranes are fabricated by vacuum-assisted filtration of the nanofiber dispersion and assembled into batteries as separator. The membrane properties and battery performances are characterized in detail and the effect of mPEG content on these properties is explored. It is demonstrated that aramid membranes possess good electrolyte wettability, excellent mechanical properties, and superior thermal stability, which improve the safety of lithium ion batteries. The mPEG is critical to the formation of aramid nanofibers and improves the porosity and ionic conductivity of the membranes. These fascinating characteristics and facile papermaking method endow aramid membrane potential application as separator in lithium ion batteries with superior safety. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43623.

Fluorescent microspheres of polystyrene-based Eu(III) complexes were prepared from TentaGel resin, 2,6-bisbenzimidazolylpyridine and europium nitrate. The microspheres were characterized by FTIR spectroscopy, elemental analysis, XPS measurements and fluorescence spectroscopy. Characteristic red emission under irradiation of 365 nm light from a hand-held UV lamp was observed for the microspheres either in a solution or solid-state. Fluorescent quenching was observed when the microspheres were exposed to a trace amount of diethyl chlorophosphate (DCP) in the dispersion. The material and property can be potentially used to fabricate chemosensor in the detection of organophosphates.

Terpyridine-capped poly(ethylene glycol) (PEG) was synthesized as a novel polymeric ligand and rare earth complex was prepared from Eu(NO 3 ) 3 and the telechelic macromolecules. The structure of the complex was characterized by 1 H NMR, FT-IR, UV-vis and fluorescence spectroscopy. Strong fluorescent emission of the complex was observed at 593 and 616 nm upon the excitation of 300 nm. The fluorescent emission was quenched upon addition of trace amount of diethyl chlorophosphate (DCP). And the observed K sv values for DCP were measured to be 0.568×10 3 and 0.89×10 3 L/mol for quenching at 593 and 616 nm, which indicated the detection limit for DCP was about 0.014 mmol/L. These results showed that the terpyridine-lanthanide complex could be an effective chemosensor with a potential application in the detection of organophosphates.

Novel physically crosslinked polyurethane-hexafluorobutyl methacrylate (PU-M) copolymers were prepared by the macroiniferter-controlled radical polymerization method. The chemical structures of the PU-M copolymers were characterized by FT-IR, (1)H-NMR, GPC, DSC, and XPS. The self-assembly and surface properties of the PU-M copolymers have been investigated. The results revealed that PU-M copolymers have good hydrophobility, so the hydrophobility of polyurethane could be easily adjusted by controlling the content of the hydrophobic vinyl monomers. The mechanical evaluation shows that PU-M copolymers exhibit good mechanical properties. The effects of the fluorine content on the surface properties and self-assembly of the PU-M copolymers were investigated. The morphology of the PU-M copolymers' self-assembly was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the mechanism of self-assembly was investigated. Antimicrobial property of the chlorinated PU-M copolymers against both Escherichia coli and Bacillus subtilis bacteria was examined and showed increase compared to that of pure polyurethane.

Polyurethane (PU) has widespread applications in implantable devices because of its excellent mechanical and biocompatible properties, whereas weak biostability limits its long-term implantation. The introduction of silicone rubber (SR) onto the PU surface is an effective method for improving the biostability of PU, but the adhesion of these two polymers is unsatisfactory. In this study, the surface modification of PU via grafting through the introduction of vinyl and SiH groups onto the PU surface was attempted to improve the adhesion of PU to SR. Fourier transform infrared, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were employed to investigate the graft reaction on the PU surface. The interfacial and surface morphology was characterized with scanning electron microscopy. Different PU/SR interfaces after oscillation and shear were compared as well. The results indicated that the PU surface was activated by diisocyanate, which generated free isocyanate groups for the further grafting of vinyl and SiH groups. When addition-type, room-temperature-vulcanized SR was poured onto the PU surface, the vinyl and SiH groups on the PU surface underwent an addition reaction, which improved the adhesion of PU and SR by connecting them with chemical bonds. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Novel physically crosslinked polyurethane–itaconic acid (PU–I) copolymer hydrogels were synthesized by the macroiniferter-controlled radical polymerization method. The structures of the PU–I copolymer hydrogels were characterized by 1H NMR, FTIR, GPC, and DSC. The water contact angles and self-assembly of the PU–I copolymer hydrogels have been investigated. The results revealed that PU–I copolymer hydrogels have good hydrophilicity, so the water contact angles of polyurethane could be easily adjusted by controlling the content of the hydrophilic vinyl monomers. The PU–I copolymer hydrogels were subjected to solvent-induced self-assembly in THF + water to construct a variety of morphologies. The morphology of the PU–I copolymer hydrogels’ self-assembly was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the mechanism of self-assembly was investigated.

To p robe the microstructures of ni trate est er pla sticized p olyether (NEPE) composite propellants and observe th e morphology of each constit ute in the propellant, the microstructure and elemental constitutes of NEPE propel- lants were in vestigated using scanning electron microscopy and energy disper- sive X-ray spectroscopy. The ammonium perchlorate (AP) grains had a scraggy surface and were difficult to disperse uniformly. The compatibility between the AP grain s a nd the poly mer bi nder wa s poor, espe cially for large grains. T he size di stribution range of the AP and o ctogen (HMX) grai ns in prop ellants varied from several to several hundreds μm for the for mer while for the latter from s everal to s everal tens μm. Contrast ing i mages be fore and after dissolution the propellant in trichloro methane sho wed th at the degree of crosslinking of the polymer binder was low since non-crosslinked binder on the surface areas w as e asily re moved by the solvent, and that the plasti cizer w as near the HMX grains and contributed more O to the element analysis of HMX.

Polystyrene-methacrylic core-shell nanospheres, self-assembled into face-centered-cube-like colloidal crystals with their (001) planes parallel to the substrate, have been transformed into ordered pore structures by a toluene treatment. Detailed analysis by transmission electron microscopy reveals that the morphological transformation is preceded by an internal neck formation due to selective fusion of the polystyrene-rich core material, at the contacts between the nanoparticles, followed by the selective dissolution of the polystyrene-rich cores. We have demonstrated the importance of local symmetry and compactness of the nanospheres assembly in determining the nature of the neck formation and the existence of multiscale ordered pore structures in the square facing colloidal crystals. The pseudo layer-by-layer nature of the selective dissolution of square arranged nanosphere multilayers is responsible for the observed three-dimensional pore structures.

In this work, we carried out the hybrid density functional theory (DFT) calculations in order to understand the thermal trans–cis isomerization and initial thermal decomposition of 3,3′-diamino-4,4′-azofurazan (DAAzF), 3,3′-diamino-4,4′-azoxyfurazan (DAAF), 3,3′-dinitro-4,4′-azofurazan (DAAF) and 3,3′-dinitro-4,4′-azoxyfurazan (DAAzF). The relative energy between the trans- and cis-isomer was also calculated at the B3LYP/6-311++G(d,p)//B3LYP/6-31G(d) level of theory. We found that a negative correlation existed between the relative energy and the sensitivity for these energetic azofurazan and azoxyfurazan compounds, where the higher relative energy means the lower the sensitivity. It was also found that the oxidation of azo-group could cause the decreasing in the relative energy between the trans- and cis-isomer, as well as the alteration of the isomerization mechanism. An inversion mechanism operates for azofurazan compounds (DAAzF and DNAF) while a rotation mechanism works for azoxyfurazan compounds (DAAF and DNOAF). Compared with the thermal trans–cis isomerization, the homolytic cleavage of C–N bond needs to overcome a much higher energy barrier, which indicates that the energy of the external stimulus should firstly trigger the trans–cis isomerization, rather than the breakage of C–N bond. A self-desensitization effect caused by the reversible thermal trans–cis isomerization process was firstly proposed to explain that the azofurazan and azoxyfurazan compounds are class of energetic materials with lower sensitivity. This new concept (self-desensitization effect) is expected to be useful to design the novel high density, insensitive energetic material.

In this work, we carried out the density functional theory (DFT) calculations in order to understand the molecular structures and thermal trans–cis isomerization of 3,3′-diamino-4,4′-azofurazan (DAAzF) and 3,3′-diamino-4,4′-azoxyfurazan (DAAF). We found that the azo group oxidation of DAAzF leading to the formation of DAAF induced evidently the twist of azofurazan molecule and weakened one of CN bonds connecting the furazan rings and azo group. This means that DAAzF is more stable than DAAF. In addition, the oxidation of azo group has a significant influence on the energy difference between trans- and cis-isomer of azofurazan. The energy difference between the isomers of DAAF is only about half of that of DAAzF. Furthermore, the thermal trans–cis isomerization of DAAzF and DAAF was found to follow a different mechanism: an inversion mechanism for DAAzF and a rotation mechanism for DAAF. By analyzing the reversible trans–cis isomerization process, we firstly proposed that a self-desensitization effect could be responsible for the low sensitivity of azofurazan. This new desensitization mechanism may be useful in the design of novel high energetic density material.

The C – H bond dissociation energies (BDEs) of hydroxyl-terminated polybutadiene (HTPB) binder have been computed using ab initio and density functional theory methods. Five different HTPB carbon radicals were produced by the ruptures of different C – H bonds. The structural analysis of radicals and the calculated BDEs showed that the studied C – H bonds could be divided into three groups. It was found that the weakest C – H bonds were those on the tertiary carbon atom linked to a vinyl function. The next were those on the secondary carbon attached to a vinyl function. The dissociation of these two kinds of C – H bonds determines the structure of the ultimate products during the aging of HTPB binder. The most stable C – H bonds were those in the methylene that were attached to the saturated carbon atoms.

Novel fluorinated polyurethanes (FPUs) were prepared by living radical polymerization of polyurethanes and hexafluorobutyl acrylate. The structures of the FPUs were characterized by FTIR, 1H NMR, GPC, DSC, and XPS. The fluorinated polyurethane polymerization was investigated and showed monomer conversion, and molecular weight increased with increasing reaction time. In this way, the fluorine content in polyurethane could be easily adjusted by controlling the content of the fluorinated acrylate monomer. The mechanical evaluation shows that FPUs exhibit good mechanical properties. Morphology of FPU films was observed by scanning electron spectroscopy. The effects of the fluorine content on the surface properties and oxidative stability of FPUs were investigated. FPUs films were devoid of significant surface degradation after immersion in 20% H2O2 and 0.1 M CoCl2 at 37 °C for 5 weeks. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3248–3256, 2009

Both of the PSMA colloidal monolayer and multilayer were transformed to ordered porous monolayers in large-scale through selective solvent treatment. The pore formation is an in situ structure inversion process and the core–shell-like structure of PSMA colloid plays a critical role in pore formation and stabilization. The ordered porous polymer films, prepared by this method, can be used as a template for fabricating metal dot-arrays with large areas.

In this work, a hyperbranched diazonium salt (HB-DAS), prepared through azo-coupling reaction of an AB2 monomer (N, N-bis[2-(4-aminobenzoyloxy)ethyl]aniline), was used to prepare self-assembled multilayers and ultrathin films. Multilayer films were fabricated by dipping substrates in HB-DAS and other polyelectrolyte solutions alternately in a layer-by-layer (LBL) manner. It was somewhat surprising to observe that HB-DAS forms multilayer films with either a polyanion (poly(styrenesulfonate sodium salt), PSS) or a polycation (poly(diallyldimethylammonium chloride), PDAC) through alternate deposition in the solutions. Ultrathin films were formed in a sequential growth manner by dipping the substrates in the HB-DAS solution, washing with deionized water and drying repeatedly. In all the processes, the absorbance and thickness of the thin films linearly increase as the number of the dipping cycle increases. HB-DAS/PSS multilayer possesses an obviously larger bilayer thickness and lower density compared with the other two counterparts. The drying step after each deposition is necessary for the HB-DAS ultrathin film growth through the repeated dip-coating of HB-DAS. The multilayer and ultrathin films prepared by the above methods all show high resistance to erosion by organic solvents. The multilayers and ultrathin films exhibit photoinduced dichroism upon the irradiation of a polarized Ar+ laser beam.

Millimeter-sized films of (100) facing face-centered crystals (fcc) of colloidal nanoparticles have been fabricated by self-assembly on silicon substrates and studied by both optical and scanning electron microscopy. The top surface layer sometimes also reconstructs to form a 1 x n (n varies from 2-7) superstructure. Such (100) oriented regions of the colloidal film are apt to concentrate near the edge of the substrate, and changing the width of the substrate could control the areas of the (100)-oriented domains. The formation of the square packing surface pattern is related to the shape of the meniscus at the edges of the substrate, where the particles suffer additional shear force and higher evaporation, which can be used to control the location and size of the square arrangement of nanoparticles.