Synthesis and characterization of semifluorinated polymers and block copolymers

The goal of the investigation presented here was to evaluate the influence of semifluorinated side chains on the bulk structure and the surface properties of polysulfones with different chain structure. Thus, segmented block copolymers consisting of polysulfone and semifluorinated aromatic polyester segments as well as polysulfones having semifluorinated side chains randomly distributed over the polymer backbone were synthesized and characterized. Oxydecylperfluorodecyl side chains were used because of their strong tendency for self-organization. The influence of the chain architecture on the self-organization as well as on the surface properties, particularly the wetting behavior, was examined. It could be shown that despite of the higher self-organizing tendency of block copolymers the surface properties of both polymer types are comparable and depend only on the concentration of side chains.     

Phase behavior of crystalline blends of poly(tetrafluoroethylene) and of random fluorinated copolymers of tetrafluoroethylene

In the present article, we investigate by differential scanning calorimetry (DSC) the thermal behavior (melting, crystallization, and crystal–crystal transitions) far from equilibrium of blends constituted of two crystalline polymers. In particular, the following blends are examined: PTFE–PFMVE, PTFE–FEP, and FEP–PFMVE where PTFE is poly(tetrafluoroethylene), PFMVE is poly(tetrafluoroethylene‐co‐perfluoromethylvinylether), and FEP is poly(tetrafluoroethylene‐co‐hexafluoropropylene). The two last ones are random tetrafluoroethylene copolymers with small amounts of comonomer. Our results indicate that, under the experimental investigated conditions, the blends containing PTFE do not give cocrystallization on cooling from the melt, although under very rapid crystallization conditions, quenching, the presence of the copolymer would seem to slightly influence PTFE crystallization (lower peak temperatures are observed for the crystalline transitions and the melting with respect to those of the neat homopolymer). The behavior of the FEP–PFMVE blend is completely different; in fact, our results indicate the occurrence of cocrystallization, then miscibility in the crystalline phase, for almost all compositions and all investigated experimental conditions. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 679–689, 1999     

Spherulitic growth in block copolymers and blends of miscible crystalline polymers

Spherulitic morphology and growth rate of block copolymers comprised of miscible crystalline constituents, namely poly(ethylene succinate) (PES) and poly(ethylene oxide) (PEO), were investigated. The results of the copolymers were compared with those of the blends with the same composition and molecular weight. Interpenetrating spherulites, where spherulites of one component grow in those of the other component, were observed in the copolymers as in the blends. Copolymerization, namely the connectivity of the PES and PEO blocks, reduced the spherulitic growth rate in the melt for both components. The growth inside the spherulites of the other component was discussed based on the lamellar and fibrillar (or lamella‐stack) structures, which are influenced by the interblock connectivity. Suppression of molecular mobility in the interlamellar regions resulted in the reduced nucleation and growth rate of the component growing in the spherulites of the other constituent. PES of the copolymer showed dendrites around 60 °C or above. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Morphology of Nylon-6 blends with styrenic polymers

The morphology of blends of styrenic polymers in a matrix of 75% Nylon-6 prepared in a Brabender Plasti-Corder was examined by scanning electron microscopy. Styrene/acrylonitrile copolymers (SAN) form smaller particles as the AN level increases owing to the corresponding decrease in the SAN–polyamide interfacial tension. Various styrenic polymers containing functional groups, maleic anhydride or oxazoline type, that can react with Nylon-6 during melt processing were added to the SAN phase which also led to a decrease in the particle size owing to the graft copolymer formed in situ. The effects of functional group type, amount of functional groups per chain, amount of functional polymer added, and the miscibility of the styrene/maleic anhydride (SMA) and SAN copolymers on the morphology of the styrenic phase in the Nylon-6 matrix are described. © 1992 John Wiley & Sons, Inc.     

Cocrystallization in blends of random tetrafluoroethylene fluorinated copolymers: The effect of the chain structure and crystallization conditions

The possibility of the cocrystallization of random fluorinated tetrafluoroethylene copolymers was investigated with differential scanning calorimetry and wide‐angle X‐ray scattering. In particular, mixtures composed of poly(tetrafluoroethylene)‐co‐(hexafluoropropylene) containing 8 or 1 mol % comonomer or poly(tetrafluoroethylene)‐co‐perfluoromethylvinylether (2–10 mol % comonomer) were examined. The extent of cocrystallization was determined by the difference in the comonomer content, being higher when the difference was lower, and it was favored when quenching from the melt state was adopted. Nevertheless, a key to determining the extent of cocrystallization was the behavior of counits with respect to inclusion or exclusion from the crystal lattice: when the components were different with respect to this behavior, they were not likely to be miscible in the crystal state even if the difference in the comonomer content was low. Moreover, the similarity in the crystallization rates between the components played an important role: the cocrystallization decreased as the difference in the crystallization rate increased until, when the difference became high enough, the blend became immiscible. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1477–1489, 2002     

Roll-Casting of block copolymers and of block copolymer-homopolymer blends

An improved technique for casting highly oriented films of block copolymers from solutions subjected to flow is presented. Polymer solutions were rolled between two counter-rotating adjacent cylinders while at the same time the solvent was allowed to evaporate. As the solvent evaporated, the block copolymers microphase separated into globally oriented structures. Using this method known as ‘roll-casting’ we present in this paper a study of the morphology of polystyrene-polybutadiene-polystyrene (PS/PB/PS) triblock copolymer cast with and without additional high molecular weight homopolymers. The pure copolymer films consisted of polystyrene cylinders assembled on a hexagonal lattice in a polybutadiene matrix in a near single-crystal structure. Blends of copolymer with high molecular weight polystyrene and/or polybutadiene, phase separated into ellipsoidal regions of homopolymer embedded in an oriented block copolymer matrix. Annealing the films resulted in conversion of the homopolymer regions to spheres accompanied by some misalignment of the copolymer microdomains. The morphology of these films as revealed by TEM is discussed. A brief discussion of the flow field that develops in the experimental system is also presented and its similarity to the flow field of our previous work is shown. © 1994 John Wiley & Sons, Inc.     

Synthesis and surface properties of fluorinated block copolymers containing sulfonic groups

A series of fluorinated block copolymers with different fluorinated block lengths and compositions were synthesized by atom transfer radical polymerization (ATRP), and then the block copolymers containing sulfonic groups with various sulfonation levels were successfully prepared further via a sulfonation reaction. These well‐defined block copolymers were characterized by means of Fourier transform infrared (FTIR), ¹H‐nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The surface activities of the fluorinated block copolymers containing sulfonic groups in N‐methyl pyrrolidone solution and the surface properties of the films prepared from such a solution were examined, and the experimental results showed that the fluorinated block copolymers exhibited a high surface activity in solution and quite a low solid surface energy of films, even though they contain hydrophilic sulfonic groups. The critical surface tensions of these copolymers were estimated and were comparable to that of polytetrafluoroethylene. Even more interestingly, the surface activities of the block copolymers containing sulfonic groups or sodium sulfonate groups in aqueous solution were also measured. It was found that the surface activity in aqueous solution was weaker than that in N‐methyl pyrrolidone solution and depended on both the length of the fluorinated block and the sulfonation level of the block copolymers. The surface properties of the films prepared from the block copolymers in aqueous solution were tested, and most of these films exhibited a hydrophilic surface property. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4809–4819, 2004     

Morphology of reactive PP/PS blends with hyperbranched polymers

To study the efficiency of different mechanism for reactive compatibilization of polypropylene/polystyrene (PP/PS) blends main chain or terminal functionalized PP and terminal functionalized PS have been synthesized by different methods. While the in-situ block and graft copolymer formation results in finer phase morphologies compared to the corresponding non-reactive blends, the morphology development in the ternary blend system PP/PS + HBP (hyperbranched polymer) is a very complex process. HBP with carboxylic acid endgroups reacts preferably with the reactive sites of the oxazoline functionalized PS (PS-Ox) and locates mainly within the dispersed PS-Ox phase. A bimodal size distribution of the PS-Ox particles within the oxazoline modified PP (PP-Ox) matrix phase is observed with big PS-Ox particles (containing the HBP as dispersed phase) and small PS-Ox particles similar in size like the unimodal distributed particles in the non-reactive PP-Ox/PS-Ox blends. Factors influencing the morphology are discussed.     

Linear and branched fluoroazo‐benzene chromophores with increased compatibility in semifluorinated polymers

A family of fluorinated azobenzene‐based push‐pull chromophores with one, two, and three trifluorovinyl ether (TFV) groups in linear and branched architecture was synthesized and utilized as active materials in the low optical loss electro‐optic (EO) composites. The fluorinated azobenzene chromophores exhibited increased solubility (30–50 wt %) in semifluorinated polymer host, such as perfluorocyclobutane (PFCB) aromatic ether resin after crosslinking, compared with the commercially available nonfluorinated azobenzene chromophore Disperse Red 1 (1–2 wt %). The impact of this approach on the optical properties on the polymer blends is assessed through optical propagation loss measurements and EO characterization. The resulting fluorinated EO composites showed excellent optical clarity, low birefringence, and low optical loss less than 0.5 dB/cm, while giving EO coefficients of about 3–7 pm/V at 1550 nm. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3166–3177, 2007     

Structure and properties of blends containing ethylene-methacrylate copolymers

The preparation, melting point, degree of crystallinity, mechanical properties, and morphology of a family of blends composed of a transition-metal-neutralized carboxylate semicrystalline ionomer (metal-neutralized ethylene-methacrylate copolymer) and an amorphous copolymer (styrene-4-vinyl pyridine copolymer) are described. These polymeric materials contain low levels (≤ 10.0 mol %) of interacting groups which are capable of forming interpolymeric complexes. These interactions are best described as transition metal-pyridine coordination complexes. A general characteristic of these blend systems is that the mechanical properties and morphology are directly influenced by the nature of the counterion and the specific composition ratio of amorphous to semicrystalline component. A nontransition metal counterion (sodium) is weakly interacting at best, while a transition metal counterion (zinc) is strongly interacting. Morphological studies (polarized-light microscopy and small-angle light-scattering measurements) confirm that the glassy component, if nonassociating, resides primarily in the interspherulite region, while the associating species will behave in a similar manner only after the stoichiometric ratio is reached. The morphology directly influences the stress-strain behavior of these blends. It is noteworthy that the spherulite size remains unchanged with nonassociating blends while a 50% reduction is noted in the associating blends. Thermal and wide-angle x-ray scattering measurements confirm the lamellar structure is unaffected by these associations. © 1992 John Wiley & Sons, Inc.     

Tuning salicylate‐based polymers to overcome lag time and extend release via copolymers and polymer blends

This work describes how physicochemical properties of salicylate‐based poly(anhydride‐esters) (PAEs) can be tuned for drug delivery and optimized by comparing copolymerization with polymer blending. These alterations reduced the lag time of drug release, while still maintaining a long‐term drug release profile. The chemical composition of the copolymers and polymer blends was determined by proton nuclear magnetic resonance and additional properties such as molecular weight, glass transition temperature and contact angle measurements were obtained. In vitro salicylic acid release from the copolymers and blends is studied in an environment mimicking physiological conditions. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 685–689     

Mechanical properties of glass continuous poly(cyclohexylethylene) block copolymers

The bulk mechanical properties of linear triblock and pentablock copolymers that self‐assemble into hexagonally packed cylinders with glassy, unentangled matrices of poly(cyclohexylethylene) (PCHE for a homopolymer, C for a block copolymer) with rubbery poly(ethylene‐alt‐propylene) (P) and semicrystalline polyethylene (E) minority components are examined. The tensile properties of high C content CEC triblock copolymer could not be quantified; however, CPC can plastically deform under uniaxial strain, unlike brittle PCHE. Both CECEC and CPCPC pentablock copolymers exhibited ductile tensile behavior, but the tensile properties of blends of these two pentablock copolymers show that the addition of crystallinity in the minority phase prevents strain softening after yielding and necking, which indicates that these samples deform only via crazing. On the other hand, the white gage region of CPCPC and the ability of CPCPC to neck indicate that high C content materials deform via shear yielding and crazing when the minority component is a rubbery material. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Structure and mechanical properties of talc‐filled blends of polypropylene and styrenic block copolymers

The structure–property relationships of isotactic polypropylene (iPP)/styrenic block copolymer blends filled with talc were examined by optical and scanning electron microscopy, wide‐angle X‐ray diffraction, and tensile‐ and impact strength measurements. The composites were analyzed as a function of the poly(styrene‐b‐ethylene‐co‐propylene) diblock copolymer (SEP) and the poly(styrene‐b‐butadiene‐b‐styrene) triblock copolymer (SBS) content in the range from 0 to 20 vol % as elastomeric components and with 12 vol % of aminosilane surface‐treated talc as a filler. Talc crystals incorporated in the iPP matrix accommodated mostly plane‐parallel to the surface of the samples and strongly affected the crystallization process of the iPP matrix. The SBS block copolymer disoriented plane‐parallel talc crystals more significantly than the SEP block copolymer. The mechanical properties depended on the final phase morphology of the investigated iPP blends and composites and supermolecular structure of the iPP matrix because of the interactivity between their components. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1255–1264, 2004     

Selective swelling blends of block copolymers for nanoporous membranes with enhanced permeability and robustness

Block copolymers (BCPs) are important precursors to produce membranes with well‐defined porosities. However, it remains challenging to prepare robust and affordable BCP‐based membranes. In this work, cheap commodity styrene‐butadiene‐styrene (SBS) elastic triblock copolymers are mixed with polystyrene‐block‐poly (2‐vinylpyridine) (SV) block copolymers in solutions, leading to macroscopically stable blend films upon casting because of the compatibilizer effect of PS existing in both copolymers. By soaking the blend films in ethanol, the microdomains of poly(2‐vinylpyridine) are selectively swollen and cavitated upon drying, resulting in a hierarchical structure with perforated SV phases interwoven with the SBS phases. The blend membranes with 30% SBS exhibit improved water permeability and mechanical robustness due to the presence of elastic SBS compared to neat SV membranes; meanwhile, the rejections of the blend membranes remain largely unchanged. Moreover, the blend membranes exhibit a pH‐responsive function, and homoporous SV regions are obtained by pre‐aligning the SV phases. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1617–1625     

Composition and solution properties of fluorinated block copolymers and their surface structures in the solid state

A series of diblock copolymers composed of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA₁₄₄-b-PFMA _n ) with various PFMA block lengths were prepared by atom transfer radical polymerization (ATRP). The surface structures and properties of these polymers in the solid state and in solution were investigated using contact angle measurement, X-ray photoelectron spectroscopy (XPS), sum frequency generation (SFG) vibrational spectroscopy, surface tension and dynamic laser light scattering (DLS). It was found that with increasing PFMA block length, water and oil repellency decreased, the ratio of F/C increased with increasing film depth, and the degree of ordered packing of the perfluoroalkyl side chains at the surface decreased. When the number of PFMA block units reached 10, PMMA segments were detected at the copolymer surface, which was attributed to the PFMA block length affecting molecular aggregation structure of the copolymer in the solution and the interfacial structure at the air/liquid interface, which in turn affects surface structure formation during solution solidification. The results suggest that copolymer solution properties play an important role in structure formation on the solid surface. Supported by the National Natural Science Foundation of China (Grant Nos. 50573069 and 20704038) and Program for Changjiang Scholars and Innovative Research Team in University (Grant No.IRT 0654)     

Miscibility and surface properties of fluorinated copolymer blends involving hydrogen‐bonding interactions

The miscibility and underlying hydrogen‐bonding interactions of blends of a fluorinated copolymer containing pyridine and a nonfluorinated copolymer containing methacrylic acid were studied with differential scanning calorimetry (DSC), transmission Fourier transform infrared (TX‐FTIR) spectroscopy, and X‐ray photoelectron spectroscopy (XPS), whereas the surface properties of the blends were investigated with contact‐angle measurements, time‐of‐flight secondary‐ion mass spectroscopy, XPS, and attenuated total reflectance Fourier transform infrared spectroscopy. DSC studies showed that the presence of a sufficient amount of 4‐vinylpyridine units in the fluorinated copolymer produced miscible blends with the nonfluorinated copolymer containing methacrylic acid. TX‐FTIR and XPS showed the existence of pyridine–acid interpolymer hydrogen‐bonding interactions. Even though the anchoring effect of hydrogen bonding hindered the migration of the fluorinated component to the blend surface, it could not completely eliminate the surface enrichment of the fluorinated component and the surface rearrangement of the fluorinated pendant chain. The air–blend interface was mainly occupied by the fluorinated pendant chain, and the surface energies of the blends were extremely low, even with only 1.5 wt % of the fluorinated component in the blends. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1145–1154, 2004     

Synthesis and characterization of conjugated polymers and their blends for optoelectronic applications

Various polymeric blends of hole transporting materials, (such as MEH-PPV and P3HT) and electron transporting materials (such as poly(phenyl-vinyl-quinoline) and poly[2-(4-methacryloxyphenyl)-5-phenyl)-1,3,4-oxadiazole]) have been prepared and investigated. Moreover a soluble, main chain oxadiazole bearing polyether has been synthesized, aiming towards an efficient electron transporting polymeric material which was also used for blend preparation together with P3HT. A deeper investigation into their spectroscopic characteristics using, primarily, FT-IR spectroscopy, but also UV-Vis spectroscopy has been conducted. The surface morphology of these blends was investigated using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) in an attempt to gather information for their solid state properties and morphologies. Finally, DSC measurements provided additional insight into the thermal behaviour of these materials.     

Compatabilization of polystyrene/polypropylene blends by styrene–butadiene block copolymers with differing polystyrene block lengths

Compatibilization of polystyrene/polypropylene (PS/PP) blends, by use of a series of butadiene–styrene block copolymers was studied by means of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). The compatibilizers used differ in molar mass and the number of blocks. It was shown that the ability of a block copolymer (BC) to participate in the formation of an interfacial layer (and hence in compatibilization) is closely associated with the molar mass of styrene blocks. If the styrene blocks are long enough to form entanglements with the styrene homopolymer in the melt, then the BC is trapped inside this phase of the PS/PP blends, and its migration to the PS/PP interface is difficult. In this case, the BC does not participate in the formation of the interfacial layer nor, consequently, in the compatibilization process. On the other hand, the BC's with the molar mass of the PS blocks below the critical value are proved to be localized at the PS/PP interface. This preferable entrapping of some styrene–butadiene BC's in the PS phase of the PS/PP blend is, of course, connected to the differing miscibility of the BC blocks with corresponding components of this blend. Although the styrene block is chemically identical to the styrene homopolymer in the blend, the butadiene block is similar to the PP phase. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1647–1656, 1999     

Morphology and micromechanical behaviour of styrene/butadiene block copolymers and their blends with polystyrene

The correlation between the morphology and the deformation mechanism in styrene/butadiene block copolymers having modified architecture and in blends with homopolymer polystyrene (hPS) was studied. It was demonstrated that the morphology formation in the block copolymers is highly coupled with their molecular architecture. In particular, the micromechanical behaviour of a star block copolymer and its blends with polystyrene was investigated by using electron microscopy and tensile testing. A homogeneous plastic flow of polystyrene lamellae (thin layer yielding) was observed if the lamella thickness was in the range of 20 nm. The deformation micromechanism switched to the formation of craze-like deformation zones when the average PS lamella thickness changed to about 30 nm and more.     

Jacketed polymers: Controlled synthesis of mesogen‐jacketed polymers and block copolymers

The controlled radical polymerization of mesogen‐jacketed liquid crystalline polymers has triggered great interests in synthesis of complex structures as well as well‐defined linear homopolymers with controlled molecular weight and narrow molecular weight distributions. This review highlights the synthetic strategies of controlled radical polymerization of linear homopolymers, star polymers, superbranched polymers, graft polymers, block copolymers, star block copolymers, and so on. The employed living methods include nitroxide‐mediated radical polymerization and atom transfer radical polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 319–330, 2009