Adhesive properties of ABA poly(styrene-b-isoprene) block copolymers

ABA poly(styrene-b-isoprene) block copolymers with various molecular weight and elastomeric content were used as heat activated adhesives. The shear strength of glass to glass joints was tested. The influence of activation temperature and ageing on shear strength was also examined. Good adhesive and cohesive behaviour was found for copolymers with low total molecular weight and identical block lengths. These results were explained by the fact that phase separation does not easily occur in such copolymers.     

Nanostructured silica-type hybrids from poly(styrene-b-ethylene oxide-b-caprolactone) copolymers

By employing a triblock copolymer, poly(styrene-b-ethylene oxide-b-caprolactone) copolymer, as a structure-directing agent, a series of silica-type hybrid materials were prepared via a sol-gel method of (3-glycidyloxypropyl) trimethoxy silane and aluminum sec-butoxide. Small angle X-ray scattering and transmission electron microscopy analyses demonstrated that ordered nanostructures, from lamellar to 2-dimensional hexagonal columnar with a disordered intermediate morphology, were exhibited as a function of the amount of loaded silica nanoparticles. Among the observed morphologies, the silica particles in the lamellar sample were localized at the PS/PEO interface, which could be elucidated by the dominant translational entropy of small silica particles.     

Morphology and mechanical and dynamic mechanical properties of linear and star poly(styrene-b-isobutylene-b-styrene) block copolymers

The morphologies of solution cast linear and star poly(styrene-b-isobutylene-b-styrene) (SIBS) block copolymers, of ∼0.3-0.33 polystyrene (PS) volume fraction, were investigated using transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) methods. The linear (L) and 4-arm star materials have hexagonal packed cylinder morphologies. TEM indicates more continuous domains for the 3-arm SIBS and SAXS indicates lamellar morphology. The diameters of the PS cylinders are 25-30 nm in all cases, but inter-domain distances increase in the order: L→3-arm star →4-arm star SIBS. Dynamic mechanical analysis shows a decrease of plateau modulus in the order L→3-arm →4-arm star. T_g for the PIB phase is independent of star-branching. T_g increases for the PS block phase from L- to 3-SIBS although T_g(PS) for 4-SIBS is not significantly greater than that of L-SIBS. A high temperature shoulder on the PIB block glass transition peak is associated with sub-Rouse motions. Tensile modulus is essentially the same for L- and 3-SIBS but considerably greater for 4-SIBS. Stress levels and energy-to rupture increase in the order: L-SIBS <3-SIBS <4-SIBS and this behavior is rationalized in terms of the covalent junction points, entanglements, and hard block domain reinforcement. The results of cyclic deformation studies of hysteresis vs. maximum percent strain per cycle are interpreted in terms of irreversible morphological rearrangements, chain slippage through entanglements, and the influence of degree of star branching on motional constraints. There is a permanent set that increases while the stress required to extend the sample to a given strain decreases with each cycle. For cycles of lower maximum strain, and before PS block domains are disrupted, microscopic deformation is viewed as somewhat reversible, accompanied by a measure of energy dissipated as a consequence of slow relaxation kinetics of chain rearrangement vs. rate of bulk deformation. At high strain, a major fraction of the energy loss is attributed to irreversible, longer ranged disruption of the PS domains leading to permanent morphological change and permanent set. Percent hysteresis for all three cases decreases—then increases—with increasing maximum percent strain per cycle. The initial decrease is thought of in terms of a progressive decrease in the entropy of stretched chains with consecutive extensions where the chains are increasingly less able to contribute to hysteresis until the PS domains become disrupted on a large scale, after which the curves begin to rise.     

Dynamic mechanical properties of annealed sulfonated poly(styrene-b-[ethylene/butylene]-b-styrene) block copolymers

Solution cast films of lightly sulfonated styrene-b-[ethylene-co-butylene]-b-styrene, (sSEBS) block copolymers were annealed for various times at 120 °C and thermal transitions are evaluated using dynamic mechanical analysis. Increased annealing time and increase in degree of sulfonation increases T_g for the PS phase while T_g for the EB phase is practically unchanged, and in some cases, there is suggestion of a relaxation due to EB-PS inter-phases. Annealing has a minor effect on the rubbery plateau storage modulus. Thus, annealing primarily alters the PS block phase. EB-PS phase separation appears to be refined with increasing SO₃H content. The region of rubber elasticity extends to higher temperatures with increased degree of sulfonation. A high temperature dynamic mechanical transition that is tentatively attributed to disruption of SO₃H—rich sub-domains within the PS block domains shifts to higher temperature with annealing.     

Highly ordered microstructures of poly(styrene-b-isoprene) block copolymers induced by solution meniscus

Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3 nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where [111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1 mm². Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation.     

Viscoelastic properties and morphology of sulfonated poly(styrene-b-ethylene/butylene-b-styrene) block copolymers (sBCP), and sBCP/[silicate] nanostructured materials

Self-assembled organic/inorganic hybrid materials were created via domain targeted sol-gel reactions of tetraethylorthosilicate in solution with sulfonated poly(styrene-b-[ethylene-co-butylene]-b-styrene) (sSEBS) copolymers. Dynamic mechanical analyses (DMA) of these hybrid materials suggest that the silicate component preferentially incorporates within the sulfonated polystyrene (PS) domains. An irreversible order-order transition (OOT) for unmodified SEBS, sSEBS, and the organic/inorganic hybrids was identified using DMA in shear mode. The OOT temperature increases with sulfonation as well as by adding a silicate phase by the sol-gel process. The DMA results imply a morphological shift with sulfonation, and reflect modified interactions within and between phases. Atomic force microscopy (AFM) indicated a shift from hexagonally packed cylinders in unmodified SEBS to a lamellar morphology in the sulfonated materials, but silicate incorporation did not affect the morphology or domain dimensions. The latter result is evidence for sol-gel polymerization templating in a self-assembly process. The phase-separated morphology is stable up to the degradation temperature of the polymer and thermogravimetric analysis revealed that the degradation temperature is unaffected by silicate incorporation. Small angle X-ray scattering data are in harmony with the structures revealed by AFM in terms of degree of order and scale of features. These results are largely rationalized in terms of chain mobility restrictions due to hydrogen-bonding interactions between different sulfonated PS blocks, an increase in the PS-ethylene/butylene block mixing parameter, increased interfacial surface tension and chain restrictions posed by inserted silicate nanostructures in the case of the hybrid materials.     

Synthesis and bulk properties of poly(tetrahydrofuran)-poly(2-methyl-2-oxazoline) ABA triblock copolymers

A series of linear triblock-copolymers of the ABA type in which the central B-block is poly(tetrahydrofuran) (polyTHF) and the A-segments are poly(2-methyl-2-oxazoline) (polyMeOX) were synthesized by a one-pot sequential monomer addition copolymerization, utilizing the living nature of the cationic ring-opening polymerization of both monomers. Films of the copolymers, casted from chloroform solutions, exhibit excellent mechanical properties in comparison with the homopolymers with comparable molecular weights, which was ascribed to the phase separation occurring between the two copolymer segments. Materials, in which the polyTHF B-segment have a molecular weight 13 000 g/mol or higher and each polyMeOX A-block a molecular weight 1500 g/mol, kept elastomeric properties up to 130 °C notwithstanding the fact that this temperature is considerably higher than the melting point of polyTHF and the glass transition temperature of polyMeOX. It was found that these triblock-copolymer materials show a shape memory effect. These observations are attributed to the high degree of phase separation between the two blocks and the strong polar interactions between the polyMeOX segments. Received: 20 March 1997/Revised: 5 September 1997/Accepted: 8 September 1997     

ABA triblock copolymers from poly(p‐dioxanone) and poly(ethylene glycol)

Poly(p‐dioxanone)–poly(ethylene glycol)–poly(p‐dioxanone) ABA triblock copolymers (PEDO) were synthesized by ring‐opening polymerization from p‐dioxanone using poly(ethylene glycol) (PEG) with different molecular weights as macroinitiators in N₂ atmosphere. The copolymer was characterized by ¹H NMR spectroscope. The thermal behavior, crystallization, and thermal stability of these copolymers were investigated by differential scanning calorimetry and thermogravimetric measurements. The water absorption of these copolymers was also measured. The results indicated that the content and length of PEG chain have a greater effect on the properties of copolymers. This kind of biodegradable copolymer will find a potential application in biomedical materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1092–1097, 2006     

Concentrated solution rheology of an ABA poly(styrene-b-butadiene) copolymer in various solvents

The critical concentrations of an SBS copolymer in cyclohexane, carbon tetrachloride, toluene, tetralin and cyclohexanone were determined. Using an equation proposed by Cornet, it was shown that at the critical concentrations the unperturbed root mean square end to end distances were, within experimental error, the same as that found for dilute solutions, indicating that the interpenetrating conformation of the blocks established for dilute solutions was maintained up to at least the critical concentrations.     

Viscoelastic properties of poly(ethylene-co-styrene) copolymers

The viscoelastic properties of narrowly distributed linear poly(ethylene-co-styrene) copolymers with different mole fractions of styrene (x_S = 0–20.5 mol %) and molecular weights (M_w = 64–214 kg/mol) were analyzed in the molten state at different temperatures by means of oscillatory rheometry. Analyzing the thermorheological properties of the polymers, we found that the time temperature superposition principle is fulfilled. The corresponding shift factors follow up to 16.5 mol % of styrene units the Arrhenius behavior of neat polyethylene. For a styrene content of about 20 mol %, the polymers no longer crystallize and a transition from Arrhenius to WLF behavior of pure polystyrene was observed. The zero shear viscosity, η₀, of the polymers was derived from the mastercurves. The determination of the plateau modulus by the well-known tan δ-min criterion is not possible due to the beginning crystallization in the corresponding temperature range. An approximate calculation of this value is based on the characteristic relaxation time λ_x = 1/ω_x, corresponding to the crossover of G′ and G′. Indeed, the characteristic modulus G_px calculated as η₀/λ_x is a good approximation for the plateau modulus G_p. The viscosity–molecular weight and relaxation time–molecular weight scaling relations were established for three copolymers with different molecular weights and nearly the same styrene content. For both material parameters, the scaling exponent is around 3.4, confirming the linear architecture of the investigated polymers. The mixing rules describing the change of such material parameters like zero shear viscosity or plateau modulus independent of styrene content are of logarithmic linear character using the weight fraction of styrene units instead of the mole fraction. The relations found allow the prediction of melt state properties for polymers with arbitrary styrene content. In the future, when catalysts with sufficient activity for the synthesis of high styrene content copolymers are available, these predictions will have to be checked. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:209–215, 1997     

Effect of multifunctional comonomers on the properties of poly(ethylene terephthalate) copolymers

The properties of poly(ethylene terephthalate) (PET) and its copolymers containing 0.04–0.15 mol% of pentaerythritol and trimethylolethane (TME) have been investigated. The molecular weight of the copolymers increased with comonomer content, and this effect was observed significantly with pentaerythritol copolymers, resulting in broad molecular weight distribution. The comonomer effect on the mechanical properties was small. The shear viscosity of the copolymers showed shear thinning within the experimental shear rate range. The crystallization rate and birefringence of the fibres containing 0.103 mol% pentaerythritol increased with the spin draw ratio, whereas they decreased with comonomer content. © 2002 Society of Chemical Industry     

Synthesis,structure, and physical properties of poly(trimethylene terephthalate)-block-poly(caprolactone) copolymers

The series of poly(trimethylene terephthalate)-block-PCLT (PTT-block-PCLT) copolymers with different contents of PTT as rigid, and poly(caprolactone) (PCL) as flexible segments have been synthesized from dimethyl terephthalate (DMT), 1,3-bio-propanediol, and PCL diol) in a two-step process involving transesterification and polycondensation in the melt. The weight amount of flexible PCLT segments varied from 0 (homopolymer PTT), 25, 35 to 45%. The molecular structure of the synthesized copolymers was confirmed by nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses. According to Hoy's method, one confirmed that PTT and PCL are likely miscible, as the difference of the solubility parameters of PTT and PCL block pairs, equals to 3.15 MPa^1/2. Moreover, the phase structure and mutual miscibility for the series of PTT-block-PCLT copolymers was characterized by differential scanning calorimetry, dynamic mechanical thermal analysis, and wide-angle X-ray scattering measurements. In copolymers with 35 and 45 wt % of flexible segments, the crystalline phase is formed during annealing above glass-transition temperature of copolymer. These copolymers during cooling at the standard rate do not crystallize. It was also found that incorporation of PCLT flexible segments, due to the macrophase separated structure, cause the decrease of the melting point and glass-transition temperature, along with the tensile modulus and tensile strength of PTT-block-PCLT copolymers, and at the same time cause an increase in the value of the elongation at break. As a result of copolymerization of PTT with PCLT, one obtained multiblock copolymers with a heterophase structure. By changing the PTT/PCLT ratio, one obtained copolymers that differ in hardness and tensile strength. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47341.     

Effect of center block structure on the physical and rheological properties of ABA block copolymers. Part II. Rheological properties

The effect of the chemical structure of the center block on the rheological properties of ABA block copolymers with polystyrene end blocks has been investigated. The chemical structure of the center blocks investigated in the present paper are polybutadiene, polyisoprene, ethylene/butene copolymer, ethylene/propylene copolymer and polydimethyl-siloxane. The chemical structure of the center block was found to have a pronounced effect on the rheological properties of the ABA block copolymer melts. The long range relaxation times of these block copolymer melts increases with increasing incompatibility between the styrene block and the center block. However, the rheological properties of the block copolymers are not influenced significantly by the glass transition or the entanglement molecular weight of the center block.     

Functionalized organic nanoparticles from core-crosslinked poly(4-vinylbenzocyclobutene-b-butadiene) diblock copolymer micelles

Surface-functionalized polymeric nanoparticles were prepared by: a) self-assembly of poly(4-vinylbenzocyclobutene-b-butadiene) diblock copolymer (PVBCB-b-PB) to form spherical micelles (diameter: 15-48 nm) in decane, a selective solvent for PB, b) crosslinking of the PVBCB core through thermal dimerization at 200-240 °C, and c) cleavage of the PB corona via ozonolysis and addition of dimethyl sulfide to afford aldehyde-functionalized nanoparticles (diameter: ∼16-20 nm), along with agglomerated nanoparticles ranging from ∼30 to ∼100 nm in diameter. The characterization of the diblock copolymer precursors, the intermediate micelles and the final surface-functionalized crosslinked nanoparticles was carried out by a combination of size exclusion chromatography, static and dynamic light scattering, viscometry, thermogravimetric analysis, ¹H NMR and FTIR spectroscopy and transmission electron microscopy.     

Effect of dialcohols on properties of poly(ethylene 2,6‐naphthalate) copolymers

Properties of poly(ethylene 2,6‐naphthalate) (PEN) and its copolymers containing diethylene glycol (DEG), propanediol (PD), butanediol (BD), and bisphenol A ethoxylate (BSA) were investigated. The copolymer composition was determined by ¹H‐NMR spectroscopy. It has a higher value than the feed composition due to the high volatility of ethylene glycol (EG). The melting temperature of the copolymers was gradually depressed with the increase of dialcohol in the composition. The complex viscosity of the copolymers did not depend on the molecular weight, but on the chemical structure. The complex viscosity of the copolymers containing 3 mol % of DEG, BD, and 5 mol % of BD was lower than that of PEN, and the mechanical properties were similar with the value of PEN. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2900–2905, 1999     

Near-surface morphology effect on tack behavior of poly(styrene-b-butadiene-b-styrene) triblock copolymer/rosin films

The correlation between near-surface morphology and tack behavior of poly(styrene-b-butadiene-b-styrene) triblock copolymer (SBS)/rosin ester films was investigated using probe tack tests, transmission electron microscopy and small-angle X-ray scattering. The SBS/rosin films with rosin composition between 10 and 20 wt% rosin, prepared by slow evaporation of toluene during solvent casting, exhibited uniform near-surface morphology of lamellae oriented parallel to the surface. However, due to the limited solubility of rosin in the PS domains, the rosin started to phase-separate from the PS domains at 15 wt%, and formed fully separated micron-sized domains above 20 wt% rosin. The probe tack force of the SBS/rosin films increased steadily when the near-surface domain orientation changed from perpendicular cylinder to parallel lamellae on addition of rosin. Specifically, for a given lamellar morphology and surface orientation, macrophase separation of rosin plays a critical role in determining the tack properties of SBS/rosin films.     

聚丁二酸丁二醇酯基共聚物及其多嵌段共聚物的合成与性能

采用“一步法”,以丁二酸酐（SAA）和1,4–丁二醇（BDO）为单体、端羟基二元醇为共聚单体合成了聚丁二酸丁二醇酯（PBS）及一系列端羟基二元醇共聚物,同时使酚酞与SAA的缩聚产物参与SAA和BDO的共聚反应,并通过链段调节合成法制备兼具刚性链段和柔性链段的可生物降解三嵌段共聚聚酯热塑性弹性体聚(丁二酸丁二醇酯-共-酚酞丁二酸丁二醇酯)（SAA-PHE-PBS）,研究了PBS及其共聚物的分子量、化学结构组成、热性能和结晶性能,此外,使用南极假丝酵母脂肪酶B测试了PBS及其共聚物的生物降解性能。结果表明,端羟基二元醇共聚物的玻璃化转变温度变化幅度不大,熔融温度无明显改变,结晶度降低,亲水性有所改善,生物降解性能得到大幅度提升;三嵌段热塑性弹性体SAA-PHE-PBS的玻璃化转变温度升高,结晶度与PBS相差不大,疏水性更强,共聚合物的残重率有所增加,生物降解性能有不同程度的降低。