Blends of polycarbonate and acrylic polymers: Crystallization of polycarbonate

The microstructure of amorphous polymer blends has been extensively studied in the past, but now there is a growing interest for polymer blends where one or more of the components can crystallize. In this study we investigate such blends, namely miscible polycarbonate (PC)/acrylic blends. Using small angle X-ray scattering (SAXS) measurements, combined with atomic force microscopy (AFM), electron microscopy (SEM), and optical microscopy, we demonstrate that the amorphous acrylic component mostly segregates inside the spherulites between the lamellar bundles (interfibrillar segregation). Varying the PC molecular weight or the mobility of the amorphous component (by changing its molecular weight and T_g) does not change the mode of segregation. So far qualitative predictions of the mode of segregation in semicrystalline polymer blends have been proposed using the δ parameter (the ratio between the diffusion coefficient D of the amorphous component in the blend and the linear crystallization rate G), introduced by Keith and Padden. Our results suggest that other parameters have to be considered to fully understand the segregation process. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2197–2210, 1998     

Preparation of substituted ionic carbohydrate polymers and their interactions with ionic surfactants

The formation of micelles of hexadecyltrimethylammonium chloride (CTAC) and sodium dodecylsulfate (SDS) in aqueous solutions containing charged polysaccharides was studied by steady-state and time-resolved fluorescence measurements using pyrene as a photophysical probe. Micropolarity studies using the I₁/I₃ ratio of the vibronic emission bands of pyrene and the behaviour of the I_E/I_M ratio between the excimer and monomer emissions show the formation of hydrophobic domains. The interactions between the polyelectrolytes and surfactants of opposite charge lead to the formation of induced pre-micelles at surfactant concentrations lower than the critical micellar concentration (cmc) of the surfactants. At similar concentrations, the I_E/I_M ratio shows a peak. This aggregation process is assumed to be due to electrostatic attractions. At higher surfactant concentrations, near the critical micellar concentration, micelles with the same properties as those found in pure aqueous solution are formed. On the other hand, systems containing polyelectrolytes and surfactants of the same charge do not show this behaviour at low concentrations. The presence of long alkyl chains bound to the polyelectrolytes also induces the formation of free micelles at concentrations somewhat below the aqueous cmc.     

Chemical recycling of polycarbonate in high pressure high temperature steam at 573 K

Polycarbonate (PC) could be completely decomposed into its monomer, bisphenol A (BPA) with high pressure (not atmospheric pressure) high temperature steam (573 K) in 5 min reaction time. The maximum yield of BPA was about 80 mol% based on the starting PC. PC decomposition at 573 K in liquid water phase near the saturated pressure for the comparison. For 30 min in reaction in liquid water at 573 K residual PC still remained and the BPA yield was about 50% as maximum.     

Preparation of emulsion‐templated fluorinated polymers and their application in oil/water separation

A series of emulsion‐templated fluorinated polymers (polyHIPEs) were first synthesized with introducing 2‐(perfluorohexyl)ethyl methacrylate (PEM) to the external phase of water‐in‐styrene high internal phase emulsion (HIPE) templates. The morphology (i.e., void size and its distribution) of these porous materials could be tuned simply by changing PEM and/or surfactant amount. The synergistic effect between the surface chemistry and surface architecture allowed the polyHIPEs to possess hydrophobicity with a water contact angle of 151°. The superhydrophobicity and oleophilicity of the polyHIPEs, together with their highly open porous structure, make the material a very competitive candidate as a filtration material for oil/water separation in practice with the efficiency of separating dichloromethane from the oil/water mixture of 95%. Such oil/water separating capacity was maintained after 10 cycles of filtration of oil/water, indicating the cyclic usage of the polyHIPE is feasible. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1508–1515     

Kinetic study of depolymerization of polyurethanes: A experimental and computational insight for chemical recycling

This work reports experimental and computational studies of polyurethanes depolymerization from industrial waste through a reaction with potassium hydroxide. A computational study was performed to identify the chemical reaction mechanism, which is more difficult to determine experimentally. Kinetic and thermodynamic parameters of activation process were also obtained by theoretical calculations. An experimental procedure led to products identified by ¹³C solid-state NMR analysis, which agree to the computational study. A small variation of less than 5% in the activation energy values found between the data obtained through theoretical calculations and experimental methods suggests that the described computational procedure is enough to describe the process in a satisfactory manner.     

Isothermal and polythermal kinetics of depolymerization of C60 polymers

Isothermal depolymerization of the two polymers of C₆₀, i.e. of 1D orthorhombic phase (O) and of “dimer state” (DS) have been studied by means of Infra-red spectroscopy in the temperature ranges 383-423 and 453-503 K, respectively. Differential Scanning Calorimetry (DSC) has been used to obtained depolymerization polytherms for O-phase and DS. Standard set of reaction models have been applied to describe depolymerization behavior of O-phase and DS. The choice of the reaction models was based primarily on the isotherms. Several models however demonstrated almost equal goodness of fit and were statistically indistinguishable. In this case we looked for simpler/more realistic mechanistic model of the reaction. For DS the first-order expression (Mampel equation) with the activation energy E_a = 134 ± 7 kJ mol⁻¹ and preexponential factor ln(A/s⁻¹) = 30.6 ± 2.1, fitted the isothermal data. This activation energy was nearly the same as the activation energy of the solid-state reaction of dimerization of C₆₀ reported in the literature. This made the enthalpy of depolymerization close to zero in accord with the DSC data on depolymerization of DS. Mampel equation gave the best fit to the polythermal data with E_a = 153 kJ mol⁻¹ and preexponential factor ln(A/s⁻¹) = 35.8. For O-phase two reasonable reaction models, i.e. Mampel equation and “contracting spheres” model equally fitted to the isothermal data with E_a = 196 ± 2 and 194 ± 8 kJ mol⁻¹, respectively and ln(A/s⁻¹) = 39.1 ± 0.5 and 37.4 ± 0.2, respectively and to polythermal data with E_a = 163 and 170 kJ mol⁻¹, respectively and ln(A/s⁻¹) = 32.5 and 29.5, respectively.     

Preparation and characterization of antimicrobial polycarbonate nanofibrous membrane

Electrospinning of polycarbonate (PC)/chloroform solution with quaternary ammonium salt (benzyl triethylammonium chloride, BTEAC) was investigated to develop antimicrobial nanofibrous membranes for ultrafiltration. With BTEAC additive, ultrafine PC fibers were continuously generated and densely mounted without the blockage of spinning tip on electrospinning. When small amounts of BTEAC were added to the PC solution, the average diameter was also decreased from several micrometers to submicron range. It was found that the conductivity of the PC solution was a major parameter affecting the morphology and diameter of the electrospun PC fibers as well as the electrospinnability of PC. The nanofibrous membranes electrospun from the PC solution with BTEAC exhibited better excellent antimicrobial activity than those prepared without BTEAC. The PC nanofibrous filter shows a good filtration efficiency to satisfy the criterion of HEPA filter, and the pressure drop of the PC filters are within the normal range. Therefore, PC nanofibrous membrane showed a great potential as a candidate for ultrafiltration, compared to a commercial HEPA filter.     

Preparation and characterization of organotin-oxomolybdate coordination polymers and their use in sulfoxidation catalysis

The organotin-oxomolybdates [(R(3)Sn)(2)MoO(4)].n H(2)O (R=methyl, n-butyl, cyclohexyl, phenyl, benzyl) have been prepared and tested as catalysts for the oxidation of benzothiophene with aqueous hydrogen peroxide, at 35 degrees C and atmospheric pressure. In all cases, the 1,1-dioxide was the only observed product. The kinetic profiles depend on the nature of the tin-bound R group and also on the addition of a co-solvent. For the tribenzyltin derivative, the apparent activation energies for sulfoxidation as a function of the co-solvent are in the order 1,2-dichloroethane (5 kcal mol(-1))相似文献   

Well‐defined epoxide‐containing styrenic polymers and their functionalization with alcohols

Polymers containing electrophilic moieties, such as activated esters, epoxides, and alkyl halides, can be readily modified with a variety of nucleophiles to produce useful functional materials. The modification of epoxide‐containing polymers with amines and other strong nucleophiles is well‐documented, but there are no reports on the modification of such polymers with alcohols. Using phenyloxirane and glycidyl butyrate as low molecular weight model compounds, it was determined that the acid‐catalyzed ring‐opening of aryl‐substituted epoxides by alcohols to form β‐hydroxy ether products was significantly more efficient than that of alkyl‐substituted epoxides. An aryl epoxide‐type styrenic monomer, 4‐vinylphenyloxirane (4VPO), was synthesized in high yield using an improved procedure and then polymerized in a controlled manner under reversible addition‐fragmentation chain‐transfer (RAFT) polymerization conditions. A successful chain extension with styrene proved the high degree of chain‐end functionalization of the poly4VPO‐based macro chain transfer agent. Poly4VPO was modified with a library of alcohols and phenols, some of which contained reactive functionalities, e.g., azide, alkyne, allyl, etc., using either CBr₄ (in PhCN at 90 °C for 2–3 days) or BF₃ (in CH₂Cl₂ at ambient temperature over 30 min) as the catalyst. The resulting β‐hydroxy ether‐functionalized homopolymers were characterized using size exclusion chromatography, ¹H NMR and IR spectroscopy, and thermal gravimetric analysis. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1132–1144     

Preparation of new microgel polymers and their application as supports in organic synthesis

A series of soluble microgel polymers have been synthesized using solution-phase polymerization reactions. In a systematic manner, several variables such as monomer concentration, cross-linker content, reaction solvent and reaction time were examined, and this provided an optimal polymer with both solubility and precipitation characteristics suitable for synthetic applications. Thus, a chemically functionalized microgel polymer was synthesized, and the utility of this polymer in the synthesis of a small array of oxazole compounds has been demonstrated. The advantage of the microgel polymers produced was that they exhibited solution viscosities lower than those of conventional linear polymers even at higher concentrations, and this was found to be beneficial for their precipitation properties. Compounds prepared using the described microgel polymer supports were obtained in similar yields and purity when compared with insoluble resins, and more importantly, the soluble polymer bound intermediates could be analyzed at each step using standard NMR techniques.     

Preparation and characterization of bismaleimides containing ester groups from bisphenolic chelates and their polymers

A series of novel metal‐containing bismaleimide monomers was prepared by the reaction of 4‐maleimidobenzoic acid chloride with bisphenolic chelates. By reaction of the synthesized bismaleimides with bis(1‐mercapto‐2‐ethylether) or 3,4‐dichloromaleimidobenzoic acid chloride, new chelating polyimidosulfides and poly(ether‐ester)maleimides were prepared. The structures of the bisphenols, bismaleimides and polymers obtained were confirmed by IR spectroscopy and elemental analysis. Characterization of the compounds was undertaken by differential scanning calorimetry, thermooptical analysis, thermogravimetric analysis, viscosity measurements and solubility tests. Copyright © 2004 John Wiley & Sons, Ltd.     

Biomacromolecule template‐based molecularly imprinted polymers with an emphasis on their synthesis strategies: a review

Molecular imprinting is an efficient tool for generating synthetic acceptors with specific recognition sites, which are mimed from template structures via polymerization. The final products of this strategy lead to high‐performance polymers with active recognition sites for a range of various applications in terms of extraction and separation, characterization and recognition, biomedicine, biosensors, and drug delivery. Molecular imprinting of biomacromolecules synthesizes a series of matrices that may be referred to as biomolecularly imprinted polymers (BMIPs). In this review article, an overview of different methods for fabricating BMIPs with an emphasis on novel polymerization schemes along with potential challenges is discussed. Additionally, selected applications of BMIPs will be briefly highlighted derived from the latest research papers. Copyright © 2016 John Wiley & Sons, Ltd.     

Measuring the size of polymers with negative radii using MALS/QELS: an exploration of the thermodynamic radius

The concept of 'size' in polymer science can have several interpretations, including definitions that rely on either statistical or equivalent-hard-sphere measures of the spatial extent of macromolecules in solution. A definition such as that of the equivalent thermodynamic radius (R(T)), which relies on the second virial coefficient of the polymer solution, offers the possibility of a zero or even a negative size parameter for macromolecules, depending on whether the polymer solution is in a theta or poor thermodynamic state, respectively. Here, we present the results of multi-angle light scattering measurements of R(T) for polystyrene and poly(methyl methacrylate), showing positive, negative, and zero values for this radius, depending on dilute solution thermodynamics. These results are augmented with measurements of the hydrodynamic radius, using quasi-elastic light scattering, and with random-walk-based calculations of the root-mean-square and viscometric radii. Re-examination of the literature provides additional examples of negative radii of polymers and oligomers.     

Structural relationships in blends of isotactic polypropylene and polymers with aliphatic sequences

Blends of isotactic polypropylene and polyethylene or polyamides often display highly unusual crystalline morphologies in which the chain axes of the helical and linear polymers are at large angles to each other. These crystalline morphologies are explained on the basis of a specific epitaxial relationship that rests on the existence, in the (010) plane of iPP, of rows of methyl groups nearly 5-Å apart. The structural basis of all the observed morphologies is the parallel alignment of the aliphatic segments of the PE or polyamides and of the iPP methyl rows (or vice versa) and matching of the near 5-Å distances between PE or PA chains and iPP methyl rows. The implications of this unusual epitaxial relationship with respect to the apparent “universality” of polymer nucleating agents are examined.     

Flammability of macrocyclic polymers and their complexes with metals

The peculiarities of thermal degradation and the flammability of nitrogen-containing macrocyclic polymers have been investigated. It has been shown that the thermal and thermo-oxidative stability of these polymers depend on the structure of the macrocycle, the type of organic radicals of the main unit and the metal nature. The effect of the type of n-conjugated macromolecules, as well as of the planarity and symmetry of macrocycle, on thermal stability as well as flammability of macrocyclic polymers has been studied. Metals (Cu, Co, Ni) in the coordination sphere increase the thermal stability and decrease the thermo-oxidative degradation of macrocyclic polymers.     

Preparation of ureido group bearing polymers and their upper critical solution temperature in water

Poly(2‐ureidoethylmethacrylate) (PUEM_n) was synthesized via reversible addition‐fragmentation chain transfer (RAFT) radical polymerization and following polymer reaction. We prepared two PUEM_n samples with different degrees of polymerization (n = 100 and 49). The polymers exhibited upper critical solution temperature (UCST) in phosphate‐buffered saline (PBS) solution. The phase separation temperature (T_p) in PBS can be controlled ranging from 17 to 55 °C by changing molecular weight of the polymer, polymer concentration, and adding NaCl concentration. The polymers in PBS formed coacervate drops by liquid–liquid phase separations below T_p. Results of the dielectric relaxation measurement, the hydration number per monomeric unit was 5 above T_p. Based on a fluorescence study, the polymer formed slightly hydrophobic environments below T_p. The liquid–liquid phase separation was occurred presumably because of weak hydrophobic interactions and intermolecularly hydrogen bonding interactions between the pendant ureido groups. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2845–2854     

Preparation and properties of polysiloxane grafting multi‐walled carbon nanotubes/polycarbonate nanocomposites

Carboxyl multi‐wall carbon nanotubes (MWNTs‐COOH) were grafted by diaminopropyl terminated dimethylpolysiloxane (DPD) to the modified MWNTs‐COOH (MWNTs‐DPD). The surface structure and thermal stability of MWNTs‐DPD and MWNTs‐COOH were characterized using Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). Then PC/MWNTs‐COOH and PC/MWNTs‐DPD nanocomposites were prepared by the solution method and melt extrusion method. The mechanical properties, transmission electron microscopy (TEM), TGA, limiting oxygen index (LOI), UL‐94 test, and permittivity test were used to evaluate the properties of the composites. The results showed that the MWNTs‐DPD was dispersed well in the PC matrix, and its tensile strength, flexual strength, flexural modulus, and flame retardancy were better than that of PC/MWNTs‐COOH. MWNTs‐DPD can improve the electrical properties of the nanocomposites at the low loading in PC. Copyright © 2010 John Wiley & Sons, Ltd.