Towards a better mixing of two incompatible polymers by casting from solution without compatibilizer

Blends of polystyrene/poly(oxyethylene) (PS/POE) and polystyrene/poly-(methyl methacrylate) (PS/PMMA) have been obtained by casting from solution. Differential Scanning Calorimetry, Optical Microscopy, and Scanning Electron Microscopy showed that two incompatible polymers can present relatively good miscibility (formation of domains smaller than 5 μm) when the solvent from which the films are obtained does not present any noticeable selectivity towards the two polymers of the blends. An increase of the casting temperature increases the miscibility of PS and PMMA because the selectivity of the solvent used, towards these polymers decreases with increasing temperature. On the contrary, an increase of the casting temperature in the case of the PS and POE mixture decreases their miscibility because the selectivity of the solvent used increases with increasing temperature. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1051–1060, 1998     

Dynamic evolution of gases in the γ‐ and helium‐ion radiolyses of solid polymers

The dynamic evolution of gaseous hydrogen, methane, and carbon dioxide in the γ‐ and ⁴He‐ion radiolyses of solid polymers was investigated. The polymers used include low‐density and high‐density polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), Nylon 11, Nylon 6, and poly(dimer acid‐co‐alkyl polyamine). An inline quadrupole mass spectrometer was utilized to monitor the dynamic profiles of the gases produced in the radiolysis. One‐ and two‐dimensional numerical diffusion models were developed to simulate and extract optimum diffusion coefficients and gas yields from the experimental dynamic gas profiles. It was found that the dynamic evolution of molecular hydrogen from the bulk polymer is controlled by its diffusion in most cases, such as CO₂ in poly(methyl methacrylate). In the γ radiolysis of some polymers such as low‐density polyethylene and polypropylene, the dynamic evolution of methane is only partially controlled by the diffusion process, and some other postirradiation process is a factor. It is concluded that the simulation method developed in this article is helpful in understanding and predicting the mechanisms of gas evolution in the radiolysis of solid polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci B Part B: Polym Phys 39: 1449–1459, 2001     

Grafting by in situ coupling of epoxy groups of a living copolymer with an anionic living polymer

A tetrahydrofuran (THF) solution of the living random copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) was prepared by the living anionic copolymerization of the two monomers, using 1,1‐diphenylhexyllithium (DPHLi) as initiator, in the presence of LiCl ([LiCl]/[DPHLi]₀ = 3), at −50°C. The copolymer thus obtained has a controlled composition and molecular weight and a narrow molecular weight distribution. By introduction of an anionic living polystyrene (poly(St)) or anionic living polyisoprene (poly(Is)) solution into the above system at −30°C, a coupling reaction took place and a graft copolymer with a polar backbone and nonpolar side chains was produced. The solvent used in the preparation of the living poly(St) or poly(Is) affects the coupling reaction. When benzene was the solvent, a graft copolymer of high purity, controlled graft number and molecular weight, and narrow molecular weight distribution (M_w/M_n = 1.11–1.21) was obtained. In the coupling reaction, the living poly(St) reacted only with the epoxy groups and not with the carbonyls of the backbone polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 105–112, 1999     

Using the new in–in method for the synthesis of polyisoprene/polystyrene heteroarm star polymers

The basis of the two‐step in–in method is as follows: star polymers with poly(divinyl benzene) cores, synthesized by the arm‐first method, include many unreacted double bonds in their core, and these double bonds can be attacked by the carbanions of some monomers such as styrene and dienes. In this work, linear polyisoprene chains were used to attack the double bonds existing in the poly(divinyl benzene) cores of polystyrene star polymers, so that a heteroarm star polymer with polystyrene and polyisoprene arms was synthesized. It was later well characterized with size exclusion chromatography, light scattering, viscometry, UV spectroscopy, dynamic mechanical thermal analysis, and ¹H NMR. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 135–142, 2003     

Linking reactions of living polymers with bromomethylbenzene derivatives: Synthesis and characterization of star homopolymers and graft copolymers with polyelectrolyte branches

Anionic polymerization techniques utilizing 1,2,4,5-tetra(bromomethyl)- benzene as the linking agent were employed for the synthesis of four-arm star polymers with poly(tert-butyl methacrylate) (PtBuMA), poly(methyl methacrylate), poly(tert-butylacrylate) (PtBuA), or poly(2-vinylpyridine) (P2VP) branches. This work was extended through the “grafting onto” method, in combination with anionic polymerization techniques, to synthesize graft copolymers consisting of polystyrene backbones and PtBuA, PtBuMA, or P2VP branches. Postpolymerization reactions were performed to produce graft copolymers with polyelectrolyte branches. Crosslinking reactions were observed in some of the graft materials several months after their preparation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4337–4350, 1999     

Studies on molecular composite. I. Processing of molecular composites using a precursor polymer for poly(p‐phenylene benzobisthiazole)

The blending of a precursor polymer for poly(p‐phenylene benzobisthiazole) (PBZT) with various matrix polymers was attempted, followed by heat conversion of the PBZT precursor polymer to obtain molecular composites consisting of PBZT and the matrix polymers. A higher concentration of mixed solution using organic solvent and milder conditions to remove the solvent could be applied to blend the polymers using the precursor polymer in place of rodlike PBZT. The dispersibility of PBZT in the matrix polymer in the blended materials obtained depended on the ability to form intermolecular hydrogen bridges between the PBZT precursor and the matrix polymer. In particular, the blended material, obtained using a nonthermoplastic aromatic polyamide as the matrix polymer having a molecular structure similar to that of the PBZT prepolymer, was transparent and showed excellent reinforcing efficiency of PBZT. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 189–197, 1999     

Synthesis of well‐defined polymers end‐functionalized with crosslinkable aziridine groups by living anionic polymerization

Well‐defined end‐functionalized polystyrene, poly(α‐methylstyrene), and polyisoprene with polymerizable aziridine groups were synthesized by the termination reactions of the anionic living polymers of styrene, α‐methylstyrene, and isoprene with 1‐[2‐(4‐chlorobutoxy)ethyl]aziridine in tetrahydrofuran at ?78 °C. The resulting polymers possessed the predicted molecular weights and narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.1) as well as aziridine terminal moieties. The cationic ring‐opening polymerization of the ω‐monofunctionalized polystyrene having an aziridinyl group with Et₃OBF₄ gave the polymacromonomer, whereas the α,ω‐difunctional polystyrene underwent crosslinking reactions to afford an insoluble gel. Crosslinking products were similarly obtained by the reaction of the α,ω‐diaziridinyl polystyrene with poly(acrylic acid)‐co‐poly(butyl acrylate). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4126–4135, 2005     

Synthesis and characterization of poly(aryl ether)s containing the pyrimidine moiety

A series of new poly(aryl ether)s containing the pyrimidine moiety were prepared by a nucleophilic aromatic substitution polymerization reaction in an aprotic solvent (DMAc) in the presence of excess potassium carbonate. These polymers are high molecular weight, amorphous, and soluble in common solvents at room temperature. The polymers are easily cast from solution into flexible, colorless, and transparent films. They showed high glass transition temperatures ranging from 198 to 304°C by DSC analysis. The 5% weight losses by thermogravimetric analysis ranged from 478 to 580°C, indicating that these polymers are very thermostable in nitrogen and air. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1107–1110, 1998     

Fast FTIR imaging: A new tool for the study of semicrystalline polymer morphology

The distribution of chemical species and the degree of orientation in semicrystalline polymer systems have been studied using fast Fourier transform infrared (FTIR) imaging. A variety of poly(ethylene glycol) systems, including pure polymer, high and low molecular weight blends, and blends with amorphous polymers, were studied. It is shown that fast FTIR imaging can be used to determine the distribution of species with different molecular weights and can be used to determine the degree of segregation of different components in blends with amorphous polymers. Additionally, by employing an infrared polarizer, the degree of orientation was determined in these systems by the generation of spatially‐resolved dichroic ratio images. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2353–2359, 1999     

Interfacial tension in a lower critical solution temperature blend: Effect of temperature,blend composition,and deformation of the interphase

Interfacial tension is a very important material parameter in two‐phase polymer blends. It determines the morphology development during processing, which is crucial for the end‐use properties of the material. Although different techniques for interfacial tension measurement give comparable results for immiscible polymers, the determination of the interfacial tension in lower critical solution temperature blends is not straightforward. This is illustrated for poly(α‐methyl styrene acrylonitrile)/poly(methyl methacrylate)(PαMSAN/PMMA), a slightly incompatible polymer pair. Interfacial tension has been measured with three different techniques: small‐amplitude oscillatory shear, recovery after elongation, and elongation of a multilayer sample. The large differences in these results can be attributed to the fact that most experimental techniques determine an apparent value, rather than the thermodynamic equilibrium value, of the interfacial tension. The latter is only obtained if the measurement is performed under quiescent conditions on a system that is composed of the coexisting PαMSAN‐rich and PMMA‐rich phases. The apparent interfacial tension depends on the actual composition of the phases and on the deformation of the interface. An order of magnitude approximation for such effects has been derived from theoretical considerations. Finally, each of these apparent values can be of practical importance. If a blend is prepared by melt mixing of the pure polymers, a high apparent value of interfacial tension should be considered. If, however, a blend is prepared by phase separation of a homogeneous mixture, the thermodynamic value is important. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 679–690, 2002     

Solvent diffusion in amorphous glassy polymers

In this article, a mathematical model is proposed for predicting solvent self‐diffusion coefficients in amorphous glassy polymers based on free volume theory. The basis of this new model involves consideration of the plasticization effects induced by small molecular solvents to correctly estimate the hole‐free volume variation above and below the glass‐transition temperature. Solvent mutual‐diffusion coefficients are calculated using free volume parameters determined as in the original theory. Only one parameter, which can be predicted by thermodynamic theory, is introduced to express the plasticization effect. Thus, this model permits the prediction of diffusion coefficients without adjustable parameters. Comparison of the values calculated by this new model with the present experimental data, including benzene, toluene, ethyl benzene, methyl acetate, and methyl ethyl ketone (MEK) in polystyrene (PS) and poly(methyl methacrylate) (PMMA), has been performed, and the results show good agreement between the predicted and measured values. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 846–856, 2000     

Reconcentration of diluted polymer solutions by full adsorption/desorption procedure: II. Desorption of macromolecules by a narrow pulse of displacer

Diluted polymer solutions can be effectively reconcentrated applying full adsorption/desorption processes. Macromolecules from diluted solutions are quantitatively retained within a bed of appropriate adsorbent. Next, the polymer is released by a high‐strength desorbing liquid that is introduced into the sorbent bed as a narrow pulse. To evaluate the above reconcentration procedure, medium‐polarity polymers, mainly poly(methyl methacrylate)s of various molar mass distributions were chosen as model species. Nonporous silica was used as an adsorbent, toluene and chloroform as adsorbing liquids, and tetrahydrofuran as a desorbing liquid in an HPLC‐like apparatus. The concentration profiles of both the desorbing liquid pulse and desorbed polymer were monitored with the usual LC detectors. On‐line size exclusion chromatography was employed in selected cases to determine molar mass and molar mass distribution of desorbed macromolecules. The effect of some experimental parameters on the reconcentration efficiency was elucidated, viz. the nature of the sample solvent‐adsorbing liquid, flow rate of desorbing liquid, molar mass, molar mass distribution, and nature of reconcentrated polymer, as well as relations among the amount of the polymer to be reconcentrated and the volume of the desorbing liquid pulse. It is shown that very high reconcentration factors can be readily obtained by the full adsorption–desorption procedure if the experimental conditions are carefully optimized. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 267–275, 1999     

Influencing the phase transition temperature of poly(methoxy diethylene glycol acrylate) by molar mass,end groups,and polymer architecture

The easily accessible, but virtually overlooked monomer methoxy diethylene glycol acrylate was polymerized by the RAFT method using monofunctional, difunctional, and trifunctional trithiocarbonates to afford thermoresponsive polymers exhibiting lower critical solution temperature‐type phase transitions in aqueous solution. The use of the appropriate RAFT agent allowed for the preparation and systematic variation of polymers with defined molar mass, end‐groups, and architecture, including amphiphilic diblock, symmetrical triblock, and triarm star‐block copolymers, containing polystyrene as permanently hydrophobic constituent. The cloud points (CPs) of the various polymers proved to be sensitive to all varied parameters, namely molar mass, nature, and number of the end‐groups, and the architecture, up to relatively high molar masses. Thus, CPs of the polymers can be adjusted within the physiological interesting range of 20–40 °C. Remarkably, CPs increased with the molar mass, even when hydrophilic end groups were attached to the polymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A new process for producing polyamide from polyester

A new process for producing polyamide from polyester and diamine was proposed. An attempt was made to produce polyamide 6T from polyethyleneterephthalate or dimethylterephthalate with hexamethylenediamine in water, o‐dichlorobenzene and sulfolane. Characterization of the products by IR, elemental analysis, solution viscosity and GPC were carried out. It became clear that high molecular polyamide 6T could be obtained from polyethyleneterephthalate and hexamethylenediamine in sulfolane. The reaction mechanism was discussed from the viewpoint of the polymer effect and solvent effect. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1413–1423, 1999     

Theoretical consideration of the molecular mass distribution of starlike polymers formed by attachment of linear polymers to dendritic cores

Star‐shaped polymers can be synthesized by condensation of linear polymers to dendritic cores. The distribution of molecular masses of such hybrid star polymers and the factors influencing it have been investigated by calculations based on population balance equations and Laplace transformations. Moreover, the expressions for numerical calculations of molecular mass distributions have been derived for both Poisson and Schultz–Zimm types of initial molecular mass distributions. According to the calculation results, the molecular mass distribution of the star polymers is strongly dependent on the distribution of the length of linear polymers. Beyond this, the molecular mass development is affected by several parameters that describe the reaction degree of dendritic cores, thus, by the fraction of all functional groups of dendritic cores involved in grafting, denoted by p; the average branching degree of one starlike molecule, represented by ρ; or the fraction of dendritic molecules becoming the cores of star polymers, expressed by p/ρ, provided the star molecule contains only one core. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2751–2758, 2001     

Brittle‐ductile transition in uniaxial compression of polymer glasses

We carried out a large set of tests to establish a correlation between the molecular (network) structure (influenced by molecular weight, molecular weight distribution, and melt predeformation) and mechanical responses of several glassy polymers to uniaxial compression at different temperatures and different compression speeds. The experimental results show that to have ductile responses there must be an adequate chain network, afforded by the interchain uncrossability among sufficiently long chains. Specifically, polystyrene (PS) and poly(methyl methacrylate) of sufficiently low molar mass do not have chain network and are found to be very brittle. Binary PS mixtures are brittle at room temperature when the volume fraction of the high‐molecular‐weight component is sufficiently low (e.g., at and below 27.5%). Moreover, sufficiently melt‐stretched PS mixtures show brittle fracture when compressed along the same direction, along which melt stretching was made. All the experimental findings confirm that a robust chain network is also a prerequisite for yielding and ductile cold compression of polymer glasses, as is for extension. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 758–770     

In vitro hemocompatibility and cytotoxicity study of poly(2‐methyl‐2‐oxazoline) for biomedical applications

Since poly(2‐methyl‐2‐oxazolines) (PMeOx) attract high attention for the potential use in drug delivery, cytotoxicity, and hemocompatibility of a set of PMeOxs with molar masses in the range from 2 to 20 kDa are systematically investigated under standardized conditions in terms of molar mass, concentration and time dependency. PMeOx polymers are well tolerated in red blood cell aggregation and hemolysis assays without any damaging effects even at high concentrations up to 80 mg/mL. Only in long term cytotoxicity tests PMeOx polymers moderately influence cell viability in a time, concentration, and molar mass dependent manner. Referring to these results it can be concluded that PEtOx could be promising nonionic hydrophilic polymers for many biomedical applications without any cyto‐ and hemotoxic effects at typically used therapeutic doses. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Investigation of the LCST of polyacrylamides as a function of molecular parameters and the solvent composition

The paper investigates the thermoprecipitation of two macromolecule structures, poly(N-isopropylacrylamide) (poly-NIPA) and poly(N,N-diethylacrylamide) (poly-DEA) from aqueous solution. The majority of the data are collected for small (M_w < 5000 g/mol) homogeneous (D < 1.3) molecules of the indicated type synthesized by anionic, group transfer, and radical polymerization in the presence of a chain transfer agent. Conventional radical polymers (M_w < 200,000 g/mol) are also synthesized and used for comparison. Turbidity curves (photometry) and transition enthalpies (high sensitivity differential scanning calorimetry) are measured to investigate the phase transition as a function of the molecular size and the tacticity as well as the concentration of certain solution additives (simple salts, glucose, and the surfactant tetrabutylammonium acetate) and mixtures thereof. Where applicable, the results are interpreted on the basis of a two-state model to gain insight in the cooperativity of the transition. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2977–2989, 1999     

Synthesis and properties of multiblock copolymers consisting of poly(L‐lactic acid) and poly(oxypropylene‐ co‐oxyethylene) prepared by direct polycondensation

A multiblock copoly(ester–ether) consisting of poly(l ‐lactic acid) (PLLA) and poly(oxypropylene‐co‐oxyethylene) (PN) was prepared and characterized. Preparation was done via the solution polycondensation of a thermal oligocondensate of l ‐lactic acid, a commercially available telechelic polyether (PN: Pluronic‐F68), and dodecanedioic acid as a carboxyl/hydroxyl adjusting agent. When stannous oxide was used as the catalyst, the molecular weight of the resultant PLLA/PN block copolymers became very high (even with a high PN content) under optimized reaction conditions. The refluxing of diphenyl ether (solvent) at reduced pressure allowed the efficient removal of the condensed water from the reaction system and the feed‐back of the intermediately formed l ‐lactide at the same time in order to successfully bring about a high degree of condensation. The copolymer films obtained by solution casting became more flexible with the increasing PN content as soft segments. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1513–1521, 1999     

Controlled synthesis of hydrophilic concentrated polymer brushes and their friction/lubrication properties in aqueous solutions

Polymer brushes of water‐soluble polymers, poly(2‐hydroxyethyl acrylate) (PHEA) and poly(poly(oxyethyleneglycol)methylether acrylate) (PPEGA), were synthesized on a silicon wafer and a silica particle by applying photo‐induced organotellurium‐mediated radical polymerization to surface‐initiated graft polymerization. High graft densities were obtained, corresponding to reduced graft densities of about 0.32 and 0.42 for the PHEA and PPEGA brushes, respectively. These values were high enough to be categorized in the regime of “concentrated” polymer brushes (CPBs). Atomic force microscopic (AFM) study revealed that the CPB of PPEGA was allowed to be highly swollen in water but the CPB of PHEA did not. This means that water is reasonably good for PPEGA but not for PHEA. The AFM microtribological study between swollen brushes revealed two lubrication regimes, namely, boundary‐ and hydrodynamic‐lubrication regimes, with different shear‐velocity dependencies. Reflecting insufficient quality of water as a solvent, the CPB of PHEA showed adhesive interaction and thereby a higher frictional coefficient μ in the boundary lubrication. More interestingly, super lubrication was achieved for the CPB of PPEGA with a μ value in the order of 10^?4 in water and in 0.1 M aqueous NaCl solution (without the help of electrostatic repulsion). Super lubrication was concluded to be a characteristic feature of the CPB, even in an aqueous system. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011