High molecular arborescent polyoxyethylene with hydroxyl containing shell

Arborescent polyoxyethylene of high molar mass (2×10⁵ g/mol) and narrow molar mass distribution was synthesized in a three-stage process. In the first stage a triblock copolymer of ethylene oxide (central block, DP ca. 90) and 2,3-epoxypropanol-1 (short flanking blocks, DP ca. 5) was synthesized. The potassium alcoholate derived from this copolymer was used to initiate the polymerization of ethylene oxide and the subsequent addition of protected glycidol (1-etoxyethyl glycidyl ether). After deprotection the short polyglycidol blocks were used as branching units for the next generation. Repeated step by step process leads to the ‘pom-pom like’ branched polyoxyethylene macromolecules enriched with the reactive hydroxyl groups in the outer shell. The branched structure of the obtained polymers was evidenced by the size exclusion chromatography and NMR spectroscopy.     

Properties of random and block copolymers of butadiene and styrene. II. Melt flow

Flow curves, log (rate of shear) versus log (shear stress), as functions of temperature were obtained for several butadiene-styrene copolymers of fixed (25%) styrene content, differing in monomer sequence distribution. A random copolymer of constant composition along the polymer chain and narrow molecular weight distribution (MWD) exhibited behavior similar to linear, narrow MWD polybutadienes; the flow was Newtonian at low shear stresses, and the flow curves for various temperatures were accurately superimposable by a shift along the log (shear rate) axis. In a random copolymer varying in composition along the polymer chain, non-Newtonian behavior was more pronounced, and temperature-shear rate superposition did not succeed, a trend further perpetuated in copolymer of a single long styrene block sequence. The latter resemble branched polymers, as would be expected from association of the styrene blocks. With two styrene blocks, association produces network structures below the glass transition of polystyrene with consequent loss of flow. Disruption of these associations above T_g (styrene) imparts the greatest thermoplasticity to these elastomers. There is evidence, however, that some of the associations persist at temperatures well in excess of T_g (styrene).     

Polymeric nanoparticles with tunable architecture formed by biocompatible star shaped block copolymer

An amphiphilic star shaped block copolymer, based on well known biocompatible components, was synthesized using branched poly(ε-caprolactone) as hydrophobic core and branched poly(ethyleneglycol) as hydrophilic corona. The composition of this macromolecule, based on two well differentiated blocks, conferred amphiphilic behavior to the whole system that acted as driving force for its self-assembling in aqueous media. Depending on the polymer concentration it was possible to obtain different architectures. The TEM micrographs permitted to follow the evolution of the system from single vesicles toward necklace entanglements. In this work, we discuss the mechanism that would be involved in the evolution of the system's morphology as a function of the block copolymer concentration. In addition, the proposed star shaped block copolymer presented good solubilizing properties that were used to disperse in water, poorly soluble molecules such as chlorine-carbazoles, which were used to investigate the suitability of the self-assembled nanostructures as drug nano-carriers.     

Rapid FTIR method for quantification of styrene‐butadiene type copolymers in bitumen

The mid‐IR molar absorptivity for polystyrene (PS) and polybutadiene (PB) blocks were obtained for five styrene‐butadiene‐styrene (SBS) and SB copolymers, including linear, branched, and star copolymers, and their blends with bitumen. The average absorptivity for PS and PB blocks was 277 and 69 L mol⁻¹ cm⁻¹ and it was little affected by the S/B ratio or the copolymer architecture. In the presence of bitumen, Beer's law was obeyed but the respective PS and PB absorptivity was 242 and 68 L mol⁻¹ cm⁻¹, possibly because of weak interactions between the copolymer and bitumen. The absorptivity values were used to calculate the concentration of SB‐type copolymers in blends with bitumen with an accuracy of 10% or better. The method can be used to probe the stability of bitumen–copolymer blends in storage at 165°C, to determine the copolymer concentration in commercial polymer modified bitumen (PMB), and to assess the resistance of PMB to weathering. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1034–1041, 2001     

Further studies of the saturated methyl branched fatty acids ofVernix caseosa lipid

By the method of capillary gas chromatography-mass spectrometry, we have identified 35 monomethyl and 46 dimethyl branched acids in the saturated acids of vernix caseosa lipid with chain lengths ranging from C₁₁ to C₁₈. Many other mono-, di-, and trimethyl branched acids have been partially identified. All methyl branches were found to be on the even numbered C-atoms except for some terminal iso methyl groups. Three types of dimethyl branched acids were found: those with a terminal iso structure, those with a terminal anteiso structure, and those with neither iso nor anteiso structures. The 4-methyl branch predominated for all types of branched acids. Equivalent chain length data for di- and trimethyl branched acids were determined on a Pentasil (nonpolar) wall coated capillary column and checked by calculation from monomethyl branched acid data. Mass spectral identification was performed with and without the aid of a data system. A possible mode of formation of these acids is discussed.     

Preparation and surfactancy of branched copolymers from poly(oxyalkylene)‐amine and trichlorotriazine coupling

A family of branched and block copolymers consisting of poly(oxyalkylene) segments was prepared by using 2,4,6‐trichloro‐1,3,5‐triazine as the amine coupling agent. The copolymers were characterized to have a high molecular weight of up to 22,600 g/mol (Mn) and be thermally stable due to the presence of triazine cores and reactive chloride functionalities. Using the trifunctional poly(oxypropylene)‐block amines as the starting material and a two‐step coupling process, the prepared copolymers are star‐shape or branched, multiple‐block copolymers, with a versatile solubility in water or organic solvents. Further variation in amine structures of hydrophobic poly(oxypropylene) (POP‐) and hydrophilic poly(oxyethylene) (POE‐) blocks may allow the prepared copolymers to be amphiphilic. As an example, the triazine/POP T‐5000/POE ED‐2001 copolymer behaves as a surfactant and exhibits the capability of reducing toluene/water interfacial tension until 1.3 mN/m at critical association concentration as low as 0.001 wt %. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 29–36, 2005     

Role of intermolecular interaction between hydrophobic blocks in block-selected inclusion complexation of amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide) triblock copolymers with cyclodextrins

The influence of hydrophobic interaction between poly[(R)-3-hydroxybutyrate] blocks on block-selected inclusion complexation between amphiphilic poly(ethylene oxide)-poly[(R)-3-hydroxybutyrate]-poly(ethylene oxide)) (PEO-PHB-PEO) triblock copolymers and α-cyclodextrin (α-CD) or γ-cyclodextrin (γ-CD) was studied by X-ray diffraction, differential scanning calorimetry (DSC), FTIR and ¹H NMR. Due to the stronger hydrophobic interaction at higher temperature, the amphiphilic triblock copolymer tends to aggregate to form tighter core-shell sphere with PHB block in the core and PEO in the corona. Therefore, the CD threaded onto PEO blocks cannot further slide onto the PHB block, which resulted in a highly block-selected inclusion complex formation. Moreover, the DSC results indicated that the triblock copolymer coalesced from its ICs with hot water showed an increase in microphase separation compared with the as-synthesized triblock copolymer, which further supports our hypothesis that CD only selectively includes PEO blocks of the triblock copolymer at higher temperature.     

Interfacial adhesion evaluation in (low‐density polyethylene)/elastomer blends

Low‐density polyethylene (LDPE) with different elastomers at a ratio of 50/50 wt% blends was prepared by using a co‐rotating twin‐screw extruder. Three kinds of elastomers were used: ground tire rubber (GTR), partially crosslinked butyl rubber (Kalar^®), and styrene‐butadiene‐rubber block copolymer (SBS; Kraton^®). For better characterization of interaction between polyethylene and elastomer, influence of the type of elastomer on the properties of compositions LDPE/elastomer was determined. In the studies, two types of partially crosslinked butyl rubber (differing over filler content and Mooney viscosity) and two types of SBS (differing over structure: linear/branched) were used. The influence of kind and type of elastomer on static mechanical properties (tensile strength, elongation at break, hardness), dynamic mechanical properties, thermal properties, and morphology of obtained compositions were characterized. LDPE/linear SBS copolymer blend had the best mechanical properties, as a result of better compatibility in comparison with other investigated blends. The reason for improved compatibility was an increase of mobility of chain segments in the amorphous phase of polyethylene associated with their partial plasticization by flexible polybutadiene blocks present in SBS copolymer. J. VINYL ADDIT. TECHNOL., 22:492–500, 2016. © 2015 Society of Plastics Engineers     

Self-assembly of polystyrene-b-poly(4-vinylpyridine) in deoxycholic acid melt

It is well known that amphiphilic block copolymers in selective solvents self-assemble into micellar structures, where solvophilic blocks tend to contact with solvents while solvophobic blocks are shielded from the solvents. Different from the conventional micellization in liquid systems, we report that the block copolymer, polystyrene-b-(4-vinylpyridine) (PS-b-P4VP), can self-assemble in melted deoxycholic acid (DCA) at high temperatures and the structures are retained in “solid state” after being cooled down to room temperature. Probing by transmission electron microscopy (TEM), we found that a series of self-assembled structures, including spherical micelles, wormlike micelles and vesicles can be obtained by varying the length of the block copolymers and the morphologies are dependent on the annealing temperature and time. We also demonstrate how to extract the structures that are trapped in solid state by removing DCA using appropriate solvents. The extracted vesicles, which are loaded with solid molecules, are potential for applications in nanocapsules and controlled release.     

Cylindrical phase of diblock copolymers confined in thin films. A real-space self-consistent field theory study

We have used real-space self-consistent field theory to search possible morphology of an asymmetric AB diblock copolymer thin film confined between two homogeneous hard walls. The volume fraction of the A block is fixed to be f=0.3, as expected, a cylindrical phase is stable without confinement (in the bulk). Our simulation reveals that under confinement, in addition to parallel and perpendicular cylinders, other phases, such as flat lamellae, perforated lamellae, undulated cylinders and undulated lamellae, are also stable due to the block-substrate interactions. Three new structures, i.e. undulated lamellae, undulated cylinders and parallel cylinders with non-integer period, are observed to be stable with suitable film thickness and block-substrate interaction. By systematically varying the film thickness and the interaction parameters between the two blocks, phase diagrams are constructed for typical block-substrate interactions. We compare the phase diagrams for weak and strong substrate preference and discuss the effects of confinement and substrate preference on the stability of various structures.     

Relation between molecular orientation and morphology of a multiblock copolymer melt confined in cylindrical nanopores

The morphologies of multiblock copolymer melts (for simplicity, we consider tetra blocks) and their configurations when they are confined in cylindrical nanopores were examined by Lattice Monte Carlo simulations. The dependence of their morphologies and of the configurations of the copolymers (through the radius of gyration) on the nanopore diameter, intersegment interaction energies (repulsive interaction energies between different kinds of segments of the copolymers), and attractive interactions between one kind of segments and the surface of the nanopore was investigated. The results indicate that the morphology of a copolymer melt is connected to the configuration of the copolymer chain. It was found that: (i) stacked disks are generated when the polymer chains are preferentially directed along the nanopore axis, and (ii) helixes or lamellae parallel to the nanopore axis are formed when the copolymer chains are preferentially directed normal to the nanopore axis.     

Synthesis,characterization, and photo‐responsive properties of Y‐shaped amphiphilic azo triblock copolymer

In this study, we report the synthesis, characterization, and photo‐responsive properties of a new Y‐shaped amphiphilic azo triblock copolymer composed of two isotropic polyethylene glycol (PEG) blocks and an azobenzene liquid crystalline block. The azo block, with two ending groups suitable for the azo coupling reaction, is polymerized by atom transfer radical polymerization with a synthesized initiator containing two functional terminal groups. The macromolecular diazonium salts are prepared by the diazotization of PEG terminated with an amino group. The triblock copolymer is obtained by the azo coupling reaction between the azo block and macromolecular diazonium salts in DMF under mild condition. The intermediates and the obtained triblock copolymer are characterized by ¹H NMR, FT‐IR, GPC, POM, DSC, TEM, and UV‐vis. The photoinduced isomerization behavior of the azo copolymer is investigated by UV‐vis. With the addition of water into the solution of the triblock copolymer, spherical aggregates with an average diameter of about 400 nm can be easily obtained. The aggregates are elongated when irradiated with polarized 365 nm UV light. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43695.     

Interaction between the strong anionic character of strong anions and the hydrophobic association property of hydrophobic blocks in macromolecular chains of a water‐soluble copolymer

The copolymerization of acrylamide, sodium 2‐acrylamido‐2‐methyl propane sulfonate, and styrene was carried out in a microemulsion medium, and ternary copolymers based on polyacrylamide, which contained both strong anionic groups (? SO₃Na) and hydrophobic blocks (polystyrene), were synthesized. The structures and compositions of the copolymer were characterized by various means (Fourier transform infrared, ultraviolet, and elemental analysis). The aqueous solution properties were investigated with a florescence probe technique and apparent viscosity measurements, and the interactions between the strong anionic character of the anionic groups and the hydrophobic association behavior of the hydrophobic blocks was intensively examined. After the simultaneous addition of the strong anionic groups and hydrophobic association blocks to the main chains of polyacrylamide, the synergism of the electroviscosity effect of the strong anionic groups and the hydrophobic association effect of the hydrophobic blocks obviously enhanced the apparent viscosity of aqueous copolymer solutions, and the synergism of greater salt tolerance of the strong anionic groups and the strengthened hydrophobic association of the hydrophobic blocks in brine solutions resulted in increased salt resistance for the copolymer. However, the presence of strong anionic groups (? SO) in the macromolecules weakened the intermolecular hydrophobic association effect of the copolymer in aqueous solutions to a certain degree; that is, the strong anionic groups produced a certain negative influence on the hydrophobic association effect of the hydrophobic blocks. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 714–722, 2005     

Blends of poly(d,l‐lactide) with polyhedral oligomeric silsesquioxanes‐based biodegradable polyester: Synthesis,morphology, miscibility,and mechanical property

A highly branched hybrid copolymer based on polyhedral oligomeric silsesquioxane (POSS) was designed to improve the brittleness of poly(d,l‐lactide) (PDLLA). The toughening material was synthesized using POSS‐OH as the core, which initiated the ring‐opening polymerization of ε‐caprolactone and d,l‐lactide sequentially to form the highly branched POSS‐g‐poly (ε‐caprolactone)‐b‐poly(d,l‐lactide) (POSS‐g‐PCL‐b‐PLA) copolymer with eight PCL‐b‐PLA arms. The POSS‐g‐PCL‐b‐PLA copolymer had a very good dispersion in the PDLLA matrix with the size of microdomains smaller than 1 µm when added at a low content below 10 wt %. In related to the nano‐scale size of microdomains in the blends, the crystallinity of PCL blocks was significantly suppressed. Thus, the addition of POSS‐g‐PCL‐b‐PLA is very effective to improve the roughness of the matrix polymer when added at a low content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40776.     

Long-tailed spherical aggregates formed from ABA triblock copolymer by changing the properties of selective solvent

A convenient method of tuning aggregate morphologies from amphiphilic block copolymer by adding second selective solvent is introduced in this paper. Some novel aggregate morphologies, i.e. hierarchical vesicles (and compound spherical micelles) with one or more tails, were formed by introducing a second selective solvent for core-forming blocks into the poly(4-vinyl pyridine)-b-polystyrene-b-poly(4-vinyl pyridine) ABA amphiphilic block copolymer/co-solvent/water systems. Addition of selective solvent (toluene) for core-forming blocks (PS blocks) has significant effect on the aggregate morphologies from the amphiphilic triblock copolymer. The aggregate morphologies changed from spheres to rods, long tailed solid large compound spheres, and to long tailed hierarchical vesicles by adding 0.5, 10 and 30 wt% of toluene to the organic solvent, respectively. There exists an aggregate morphological transition of the long tailed hierarchical vesicles to long tailed solid spheres by decreasing the content of toluene in the organic solvent mixture. The tails disappeared, and irregular vesicular and spherical structures were formed when the toluene content was 20 wt%. The toluene addition is expected to increase the stretching of the core-forming blocks (PS), and to modify the interfacial tension of core-corona interface, which are the main reasons for the aggregate morphology transition. To the best of our knowledge, these tailed vesicles and spherical morphologies have not been found in block copolymer aggregates system up to now.     

A study of the versatile micropatterns of diblock copolymer micelles: the effect of copolymer concentration, substrate, film thickness and micelles morphology

We report the novel use of polystyrene-block-poly(acrylic acid) (PS-b-PAA) diblock copolymer micelles as the nano-building blocks in fabricating orderly aligned three-dimensional micropatterns with high regularity through a one-step evaporation-induced cracking process. Crack patterns of square, rectangular, stripe-like and mesh-like structures in micron scale were obtained. The effect of the concentration of diblock copolymer, the properties of the substrates, the thickness of the drying layer, and the morphology of the micelles on the regularity of the crack patterns was studied. By regulating the above factors, we achieved micropatterns of various structures. We further developed a cheap, fast, and simple method for fabricating micromolded structures using the crack patterns as templates.     

One‐pot approach synthesizing and characterization of random copolymerization of ethyl acrylate‐co‐methyl methacrylate with broad range of glass transition temperature onto collagen

Collagen is a natural polymer that cannot be applied freely to specific end uses due to its inherent drawbacks. Grafting polymerization of methyl methacrylate‐co‐ethyl acrylate was applied to modify the surface of acid soluble collagen (ASC). The main objective of this work is not only reducing the hydrophilic behavior of collagen on which has been concentrated so far but also successfully showed that the introduced co‐monomers onto ASC can alter the thermal behavior of the resulted copolymer. The level of branched copolymer significantly influenced the initial viscosity in studied co‐monomer feed ratios. The graft polymerization of collagen demonstrated the meaningful change in conductivity value of branched copolymer, where the copolymer in side chain with low dielectric constant covalently bonded onto the ASC. The increase in the co‐monomer feed ratio had no significant effect on conductivity value of copolymer, afterwards. The novelty of this work was determined to achieve the new copolymer onto the backbone of collagen to be used in specific thermally stabled end uses that the sufficient chain entanglements improve the flexibility of final product. POLYM. ENG. SCI., 58:1261–1267, 2018. © 2017 Society of Plastics Engineers     

Nanostructure development in polystyrene‐b‐polybutadiene‐b‐poly(methyl methacrylate) (SBM) thin films by atomic force microscopy: Effect of copolymer composition and solvent

Surface morphology development for SBM triblock copolymer thin films has been studied by atomic force microscopy. The effect of copolymer composition and solvent on the final morphology has been investigated. Obtained results indicated that depending on the block ratio (symmetric or asymmetric with minority middle block) and solvent, lamellar, hexagonal, cylindrical, or spheres in lamellae (ls)‐type morphologies can be achieved at film surfaces. The influence of the interaction parameters among blocks and solvents and cohesive energy values of block pairs on the final morphology has been proved. POLYM. ENG. SCI., 58:422–429, 2018. © 2017 Society of Plastics Engineers     

Styrene-butadiene branched star-shaped asphalt modifiers: Synthesis and mechanical characterization

Abstract

The synthesis and the corresponding characterization of styrene-butadiene (SB), branched, star-shaped copolymers was investigated as part of a research project on asphalt modification using polymers with precise molecular structures. The method of anionic polymerization was followed to prepare samples of block copolymers of SB, a synthesis method that controls chain-architecture, molecular weight distribution, monomer distribution, and the average molecular weight. The research studies are the synthesis of block copolymers including linear, three- and four-arms constructs, depending on the coupling agent used. The techniques of nuclear magnetic resonance (1NMR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and rheology were carried out to characterize the copolymers. From the results of the 1NMR, DSC, and GPC analyses, all star-shaped copolymers investigated showed a similar block copolymer composition. Furthermore, the rheological behavior of one of the synthesized star-shaped copolymers was nearly the same as a four-branched commercial copolymer. Rheologically, the four-arm block copolymer sample had the largest storage modulus (G′) among the branched copolymers synthetized, indicating that such architecture produces a highly structured material. In regard to polymer-modified asphalt formulations, the three-branched copolymer architecture yielded better elastic behavior than the four-branch version. In summary, the findings of this investigation provide new insight about a polymer system that may offer advantages in industrial asphalt paving applications.     

Synthesis and microphase-separated structures of star-block copolymers

Highly branched star-shaped polymers such as (AB)_n stars of asymmetric diblock arms, star homopolymers, and gradient-modulus stars led to hierarchical structure transformation of cubic lattices in film formation. The ordered microphase-separated morphologies for A_nB_n and A_mB_n stars were quite different from those that occurred in the corresponding linear block copolymer systems. Thus, the particular chemical structures of star-block copolymers were influenced significantly by incompatibility effects.