Liquid-phase Polymerization Research Articles

Evidence of the filling of nano-porosity in SiO 2- like layers by an initiated-CVD monomer

Although very promising results in terms of moisture and oxygen barrier properties have been achieved by alternating organic and inorganic layers composing a multilayer structure, the impact of the organic interlayer on the global barrier performance is still unraveled. Three main hypotheses have been reported in literature so far, although consistently applied to the case of a liquid-phase polymerization process of the organic layer: smoothening of the polymeric substrate surface by the organic layer; decoupling, by means of a tortuous path, of the defects present in two adjacent inorganic barrier layers; filling of the nano-defects present in the barrier layer during the (liquid phase) polymerization of the organic layer. Within this framework, this contribution reports on the adsorption/desorption study of an initiated-CVD (i-CVD) monomer (trimethyl-trivinyl-cyclotrisiloxane), V 3D 3, performed on plasma deposited SiO 2- like layers by means of in situ spectroscopic ellipsometry measurements. The SiO 2- like layers are used as moisture permeation barriers followed by an organic interlayer deposited by means of the i-CVD technique. The experimental evidence for the V 3D 3 molecule infiltration and filling in the open micro/meso porosity present in the inorganic layer underneath, confirms the hypothesis on the filling of nano-defects in the barrier layer upon organic layer deposition and shows that the defect filling occurs also in the case of a CVD-based approach.

Preparation of novel photoreactive polycarbazole-based microparticles: Reactivity features

Four types of innovative benzophenone (BPh)- or aryl azide (ArAz)-containing photoreactive polycarbazole (polyCbz)-based microparticles (MPs) were prepared using an oxidative liquid phase polymerization system. Their photochemical reactivity was evaluated by their reaction with highly inert poly(2-chloro-paraxylelene) (Parylene C) films. Possible mechanisms for the photochemical reaction of those MPs with Parylene C were discussed. The highly photoreactive BPh was found to react more inside the particle causing internal cross-linking of MP polyCbz chains, fusion between adjoining particles and deformation of their spherical structure. In contrast, the less reactive but more selective ArAz-containing MPs were found to react much more with Parylene C. The strong reactivity of such photoreactive MPs toward Parylene C films emphasizes a general method for the functionalization of stable nonfunctional polymeric coatings. This paves the way to simple and solvent-free functionalization of nonfunctional coatings and materials by light. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Oxidative fabrication of spherical polycarbazole-based microparticles

A straightforward oxidative liquid phase polymerization (LPP) method has been successfully developed for the fabrication of spherical functional (polyCOOH) polycarbazole-based microparticles from corresponding carbazole-containing monomers. The influence of the chemical structure of starting carbazole monomers on the LPP-based microparticle formation has been deeply examined using scanning electron microscopy (SEM).

기상중합법을 이용한 Polypyrrole(PPy) 필름의 전기적/광학적 특성 및 미세패턴 형성에 관한 연구

Iron(Ⅲ) p-toluenesulfonate(FTS)를 개시제로 한 pyrrole의 중합에서 용액 중합법(LPP)과 기상 중합법(VPP)으로 제조된 PPy 박막의 전기/광학적 특성 및 표면구조를 비교하였다. LPP에 비해서 VPP 방법으로 제조된 PPy 박막은 우수한 전기적 특성을 보여주었다. 표면 특성분석을 이용하여 제조된 PPy 필름의 표면 모폴로지와 표면저항과의 상관관계를 검토하였다. VPP 방법으로 제조된 PPy 박막의 표면이 LPP로 제조된 것보다 평탄하였다. VPP를 응용한 잉크젯 프린팅과 소프트 리소그래피를 사용히여 미세 패턴된 PPy 박막을 효과적으로 제조할 수 있었다.

An easy method for the production of functional polypyrrole/MWCNT and polycarbazole/MWCNT composites using nucleophilic multi-walled carbon nanotubes

Oxidized polycarboxylated multi-walled carbon nanotubes (COOH-MWCNTs) may be readily decorated by covalently attached pyrrolyl (Pyr) and carbazolyl (Cbz)-containing ligands. Resulting chemically modified MWCNTs behave as a novel nucleophilic nanosized phase. It covalently trapped positively charged polyPyr- and polyCbz-chains grown oxidatively in bulk media of liquid phase polymerizations (LPPs). This two-step sequence for the controlled fabrication of functional (polyCOOH) dual phase polyPyr/MWCNT and polyCbz/MWCNT composites provided a general solution to the observed detrimental issues of phase compatibility during component assembly. In one specific case, this multi-parameter oxidative liquid phase polymerization process has been also investigated using a statistically relevant design of experiments in order to evaluate influential LPP parameters for process optimization.

Fabrication of functional polypyrrole (PolyPyr)-nanotubes using anodized aluminium oxide (AAO) template membranes. Compromising between effectiveness and mildness of template dissolution conditions for a safe release of PolyPyr-nanotubes

Functional acidic (COOH) pyrrole (Pyr)-containing oxidizable monomers can be template-polymerized using hard nanoporous anodized aluminium oxide (AAO) membranes in liquid phase polymerization (LPP) conditions. Accordingly, the safe and effective release of resulting functional polyCOOH–polypyrrole (polyPyr)-nanotubes from template membranes must be operated in controlled acidic, instead of commonly used Martin-like basic conditions (membrane digestion).

Thermodynamical properties of ε-caprolactone

The values of the combustion and enthalpies of formation for e-caprolactone were determined by means of combustion calorimetry. The vapor pressures of lactone were measured in the range of 283–353 K, and the value of its enthalpy of vaporization was estimated by the transpiration method. Conformational analysis and calculations of the equilibrium structures, inertia moments, and sets of fundamental vibrations was performed by the B3LYP/6-311++G(3 df, 3 pd) quantum-chemical method. The total energies of the most stable lactone conformers were found and ΔfH(g) was estimated using the composite G3MP2 method. The set of fundamental vibrations for the most stable conformers of the compound was developed on the basis of the available experimental IR spectra and calculated vibration frequencies. The values of the thermodynamic properties of e-caprolactone were determined in the ideal ga s state in the range of 0—1500 K. A set of reliable and interconsistent thermodynamic parameters for e-caprolactone was created. Thermodynamic analysis for liquid-phase polymerization of s-caprolactone in the temperature range of 220—500 K was carried out.

Adsorption of hydrogen on nanoporous carbon adsorbents

Four samples of active carbons with specific micropore volumes of 0.4—1.33 cm3g-1 at 77 K and pressures up to 5 MPa were used to study hydrogen adsorption. The highest amount of of hydrogen adsorbed on these active carbons at the boiling point 20.38 K and pressure 0.101 MPa was calculated by methods derived from the theory of volumetric filling of micropores (TVFM). The adsorbent FAS-1-05 prepared by the liquid-phase polymerization of furfurol was shown to have the highest adsorption capacity. The amounts of hydrogen adsorbed on FAS-1-05 at temperatures 77, 196, and 300 K and pressures 7 and 20 MPa were calculated using the TVFM methods with allowance for linearity of the isosters. The results were compared with the experimental values obtained at 77 K and pressure below 5.1 MPa and at 293 K and pressures up to 16.1 MPa. The highest amounts of hydrogen adsorbed (6.2 wt.% for the adsorbent FAS-1-05) were obtained under pressures below 5.1 MPa and at 77 K.

The thermodynamic properties of delta-lactones

The enthalpies of formation of δ-hexanolactone and δ-nonanolactone were determined by combustion calorimetry. Conformational analysis and quantum-chemical calculations of equilibrium structures, fundamental vibrations, moments of inertia, and total energies were performed for δ-pentanolactone (I), δ-hexanolactone (II), and δ-nonanolactone (III) by the B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and G3MP2 methods. The experimental IR spectra and calculated vibrational frequencies were used to suggest the assignment of vibrational frequencies of stable conformations. The thermodynamic properties of I–III in the ideal gas state were determined over the temperature range 0–1500 K. A thermodynamic analysis of mutual isomerization in the gas and liquid phases over the temperature range 298.15–900 K and liquid-phase polymerization of γ- and δ-pentanolactones and 4-pentenoic acid over the temperature range 298.15–500 K was performed.

Radiation-chemical processes for fabrication of protective coatings and composite materials with the use of fluorinated monomers

The feasibility and the specific features of fabrication of protective coatings and composite materials on the basis of fluorinated monomers with the use of high-energy radiation (60Co γ-rays, fast electrons) are analyzed. The consideration is focused on the radiation-chemical synthesis of tetrafluoroethylene telomers, their practical application, and modification of polymeric and inorganic materials by means of low-temperature postradiation polymerization and liquid-phase graft polymerization of fluorinated monomers. Radiation initiation makes it possible to prepare new products with a broad range of functional properties and to design novel technologies with the use of fluorinated monomers.

Heat and mass exchange in films of a reacting mixture and a cooling liquid under exothermic-reaction conditions

Conjugate turbulent heat and mass exchange in fast exothermic reactions in thin films has been investigated with allowance for the change in the pressure. A modification of the equal-flow-rate method, the most natural for problems of such a kind, has been constructed. Its distinctive feature is that it is constructed on formal passage to a rectangular domain of variation in variables. The modification obtained has been tested on the problem solved earlier by the well-known equal-flow-rate method. Despite the fact that the proposed mathematical model and the procedure of its investigation enjoy rather wide application, in the present work, it is oriented toward the cationic liquid-phase polymerization of isobutylene. The local concentration distributions of the monomer and the catalyst and the temperature distributions have been obtained in numerical investigations. The reaction and cooling zones have been singled out; it has been recorded that the process of the most active chemical transformation is localized by the narrow zone of entry into the film.

Initiated Chemical Vapor Deposition (iCVD) of Poly(alkyl acrylates): An Experimental Study

In a two-part investigation, an experimental study and a kinetic model analysis of the initiated chemical vapor deposition (iCVD) of alkyl acrylate polymers are described. In this first part, an experimental study was performed to look at the effect of process parameters on iCVD polymerization. A homologous series of alkyl acrylates, from ethyl up to hexyl acrylate, were iCVD polymerized. The resulting polymers matched well spectroscopically with those from liquid-phase polymerization, demonstrating that stoichiometric polymers with no observable cross-linking can be achieved in a chemical vapor deposition environment. Deposition rate and molecular weight increased by a factor of over 300 and 60, respectively, when monomer saturated vapor pressure, Psat, was reduced from 42.6 to 0.584 Torr at equal gas pressures, PM. Over three times increase in deposition rate was observed for ethyl acrylate when substrate temperature was reduced from 29 to 17 °C. These trends are attributed to an increase in PM/Psat or, equivalently, monomer surface concentration in Henry's law limit at low PM/Psat. Evidence for adsorption-limited iCVD kinetics came from an apparent negative activation energy of −79.4 kJ/mol obtained experimentally that agreed well with a mathematically derived activation energy of −81.8 kJ/mol equal to twice the heat of desorption in the negative sense. Adsorption measurements found Henry's law limit to be valid and, when fitted to a BET equation, allowed the heat of desorption to be calculated. On the basis of this experimental study, process guidelines were made to define the appropriate parameter space for future iCVD polymerization, with PM/Psat in the range of 0.4−0.7 recommended as an optimal iCVD window.

Polydipyrrole- and polydicarbazole-nanorods as new nanosized supports for DNA hybridization

Novel functional polydipyrrole- and polydicarbazole nanorods have been AAO template-synthesized from COOH-dipyrrole/-dicarbazole monomers using Vapor Deposition and Liquid Phase Polymerizations (VDP and LPP). They were tested as insoluble supports for covalent DNA attachment and hybridization.

Design and fabrication of unsteady electrokinetic microactuator arrays for turbulent boundary layer control

The development of a micro-electro-kinetic-actuator (MEKA) array for the study and control of the viscous sublayer of a turbulent boundary layer is presented. Several generations of such MEKA arrays have been fabricated that explore the use of non-conventional MEMS materials such as quartz, polymers or mylar and are combined where needed with conventional MEMS design and fabrication processes. The present study is the first attempt to exploit the potential advantages of using the electrokinetic principle as the basis for a new class of microscale actuators suitable for active sublayer control. Among such advantages are that these actuators have no moving parts, and that they achieve the flow rates required for this type of flow control. Moreover, the inherent problem of matching the length and time scales between microactuators and the physical system being controlled makes the viscous sublayer a natural choice for these types of actuators. The electrokinetic drivers are fabricated inside microchannels, 250 mm to 2 mm in diameter, using a liquid-phase polymerization process that generates 1 µm doped pores. This process greatly simplifies the fabrication of a large number of actuators, and using this technique we are able to fill 100% of the 25 600 microchannels that form the typical MEKA 5 array. The array is fabricated using a novel three-layer design that contains (i) a top layer with the actuator nozzles, electrodes and leadouts, (ii) a center layer containing the individually addressable electrokinetic driver channels in which electrolyte pumping occurs in response to a time-varying electric field that will induce volume displacement in the sublayer and (iii) a bottom layer containing an electrolyte reservoir and common electrode. The functionality incorporated in this three-layer design with independent unit cells demonstrate all the elements needed for turbulent boundary layer control.

Reactor design concepts for radiation processing

During the formative years of irradiation processing, the 1950s and 1960s, there was laboratory and academic interest in the use of this form of energy transfer to initiate polymerization for the manufacture of plastics and in other chemical processes. Studies were often based on low-dose-rate Cobalt-60 systems. The electron beam (EB) accelerator technology of the time was not as yet at the robust and industrially reliable state that it is now at the beginning of the twenty-first century. A series of reactor designs illustrate how an electron beam can be incorporated into reactor vessels for initiating gas and liquid phase polymerizations on a continuous basis. Development of such approaches, which would rely upon contemporary, high current electron beams to initiate polymerization, would help the chemical processing industry alleviate its problems of catalyst disposal and its related environmental concerns. Systems for treating materials in bulk at low doses, such as those typically used for grain disinfection, at high through-put rates, are also illustrated. Simplified shielding is envisioned in each proposed process system.

Modeling and simulation of propylene polymerization in nonideal loop reactors

AbstractA dynamic mathematical model for liquid‐phase polymerization in loop reactors was developed and implemented in language C using S‐functions in a MATLAB/SIMULINK environment. It is based on a nonideal continuous stirred‐tank reactor (CSTR) model capable of dealing with multisite copolymerization of olefins. The kinetic scheme includes a specific mechanism for hydrogen effect on rate of polymerization observed on both laboratory experiments and industrial plant trials. A nonideality due to polymer segregation at the reactor output was inserted into the model to better predict reactor slurry density. Polymer moment balances were used to compute resin properties, such as average molecular weights, polydispersity, and melt flow index. Dynamic data from an industrial polypropylene plant were used for parameter estimation and model validation.

Thermal degradation of the polymer obtained by oxidation of C60 fullerene by oleum

Degradation of (C60) n polymer and the C120 and C120O dimers at different temperatures was studied by IR and ESR spectroscopy. The formation of C60 was revealed. The polymer stability was found to be higher than the stability of the dimers. Peculiar features of the IR spectra of three-dimensional “hyper-crosslinked” polymers obtained by liquid-phase polymerization of C60 are discussed.

Fabrication and characterization of hydrogel-based microvalves

Several microvalves utilizing stimuli-responsive hydrogel materials have been developed. The hydrogel components are fabricated inside microchannels using a liquid phase polymerization process. In-channel processing greatly simplifies device construction, assembly, and operation since the functional components are fabricated in situ and can perform both sensing and actuation functions. Two in situ photopolymerization techniques, "laminar stream mode" and "mask mode," have been explored. Three two-dimensional (2-D) valves were fabricated and tested (response time, pressure drop, maximum differential pressure). In addition, a hydrogel/PDMS three-dimensional (3-D) hybrid valve that physically separates the sensing and regulated streams was demonstrated. Analytical modeling was performed on the 3-D valve. Hydrogel-based microvalves have a number of advantages over conventional microvalves, including relatively simple fabrication, no external power requirement, no integrated electronics, large displacement (185 /spl mu/m), and large force generation (22 mN).

On the phenomenon of variable activation energy for condensed phase reactions

Various effects that liquid and solid media produce on the experimental activation energy of a reaction involving a single chemical step are discussed. The effects are experimentally observed as significant variations in the activation energy with temperature or extent of reaction. Since these phenomena are inconsistent with the concept of a constant activation energy, that of variable activation energy is considered as an alternative. The discussion covers the kinetics of such processes as electron transfer, liquid phase polymerization, desorption from solids, and solid state decomposition.

Gas‐phase polymerization of propylene with a highly active ziegler‐natta catalyst

AbstractThe polymerization of propylene in the gas phase has been studied with the same high‐activity catalyst as was used for liquid‐phase polymerizations in earlier work. Catalyst injection, the influence of the support bed, and precontacting of the catalyst with the cocatalyst and the electron donor have been investigated. Furthermore, different ways of prepolymerization were tested. The kinetics can be described with the same model as was used for the liquid‐phase polymerizations. The reaction rate was proportional to the pressure at pressures above 5 bar; at lower pressures the rates are lower. Comparison of the reaction rates in the gas phase and liquid phase showed the rates in the gas phase were still lower than in the liquid phase. The fast decay observed in the gas‐phase polymerizations indicated that thermal runaway and deactivation may occur at temperatures above 40–45°C.