Diblock Copolymers Of Polystyrene Research Articles

Preparation of 1, 2, 3-Triazole-Functionalized Polystyrene Diblock Copolymer and Its Properties of Selective Adsorption of Proteins

Preparation of 1, 2, 3-Triazole-Functionalized Polystyrene Diblock Copolymer and Its Properties of Selective Adsorption of Proteins

Synthesis and characterization of amphiphilic methoxypoly(ethylene glycol)-polystyrene diblock copolymer by ATRP and NMRP techniques

Amphiphilic block copolymers are used in a variety of applications, for example, as stabilizers for emulsions and dispersions or as compatibilizers in polymer blends. Amphiphilic diblock copolymer composed of methoxypoly(ethylene glycol) and polystyrene (MPEG-b-PS) was synthesized using atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP). In order to synthesize MPEG-b-PS diblock copolymer using ATRP, monofunctional MPEG macroinitiator (chloroacetylated MPEG [MPEG-Cl]) was prepared from monohydroxyfunctional poly(ethylene glycol) and initiated end group on the basis of chloroacetyl chloride. ATRP was carried out in bulk using MPEG-Cl as the macroinitiator, copper chloride (CuCl)/2,2′-bipyridine (bipy) as the catalyst ([MPEG-Cl]/[CuCl]/[bipy] = 1:1:3), and styrene as the monomer. For preparation of MPEG-b-PS by means of NMRP, firstly, 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) was obtained by reduction of 2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbat. Then, TEMPO-OH was coupled with chloroacetylated MPEG (MPEG-Cl) to yield the macroinitiator MPEG terminated with a TEMPO unit (MPEG-CO-TEMPO). At last, MPEG-CO-TEMPO was further used to prepare the diblock copolymer MPEG-b-PS by ‘living’ free radical polymerization of styrene. The products were purified and identified by Fourier transform infrared (FT-IR) spectroscopy, 1H nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC).

Polymer electrolyte membranes from fluorinated polyisoprene-block-sulfonated polystyrene: Structural evolution with hydration and heating

Small-angle neutron scattering (SANS) and ultra-small-angle X-ray scattering (USAXS) have been used to study the structural changes in fluorinated polyisoprene/sulfonated polystyrene (FISS) diblock copolymers as they evolved from the dry state to the water swollen state. A dilation of the nanometer-scale hydrophilic domains has been observed as hydration increased, with greater dilation occurring in the more highly sulfonated samples or upon hydration at higher temperatures. Furthermore, a decrease in the order in these phase separated structures is observed upon swelling. The glass transition temperatures of the fluorinated blocks have been observed to decrease upon hydration of these materials, and at the highest hydration levels, differential scanning calorimetry (DSC) has shown the presence of tightly bound water. A precipitous drop in the mechanical integrity of the 50% sulfonated materials is also observed upon exceeding the glass transition temperature (Tg), as measured by dynamic mechanical analysis (DMA).

Depth distribution of different solvents in a phase-separated block copolymer thin film

The structural change induced by the contact with different solvents was investigated for a diblock copolymer thin film, of polystyrene (PS) and poly(2-vinylpyridine) (P2VP), forming a lamellar structure by in-situ neutron reflectometry with a conventional cell for the measurement on solid/liquid interfaces. In the case of methanol, which is a selective solvent for P2VP, the structural change was induced by the penetration of methanol into the film, and the original lamellar structure was almost recovered by drying the film even after the solvent contact. On the other hand, when toluene was used as a selective solvent for PS, the block copolymer thin film was easily dissolved into toluene, and its original state was never recovered after the solvent contact. Further, water induced the structural change in the block copolymer thin film similarly to methanol, though it is a poor solvent common for PS and P2VP.

Novel Route to Control Interfacial Properties of Glass Fiber-Reinforced Polystyrene Composites via a Photo-Cross-Linkable Block Copolymer Coupling Agent

A diblock copolymer of polystyrene–block–poly(2-hydroxyethyl acrylate) (PS-b-PHEA) was synthesized via atom transfer radical polymerization (ATRP) and reacted with cinnamoyl chloride in triethylamine to yield PS-b-(PCEA-co-PHEA) copolymer with photo-cross-linkable poly(2-cinnamoylethyl acrylate) (PCEA) moieties. Then the triblock copolymer of polystyrene–block–poly(2-cinnamoylethyl acrylate-co-2-hydroxyethyl acrylate)–block–poly(γ-methacryloxypropyltrimethoxysilane) (PS-b-(PCEA-co-PHEA)-b-PMPS) was synthesized viaATRP from PS-b-(PCEA-co-PHEA) copolymer. Using as-prepared triblock copolymer as a macromolecular coupling agent to modify glass fibers, via microbond tests, the interfacial bond strength between pretreated glass fiber and polystyrene was compared before and after copolymer photo-crosslinking. The partially crosslinked block copolymer coupling agent greatly improved the interfacial adhesion of glass fiber-reinforced polystyrene.

Characterization of polystyrene‐b‐poly(ethylene oxide) diblock copolymer and investigation of its micellization behavior in water

AbstractThe recent studies deal with a diblock copolymer, polystyrene–poly(ethylene oxide). Infrared spectroscopy, proton resonance spectroscopy (1H‐NMR), and laser light scattering techniques have been used to characterize the polymer. It has been concluded that the sample investigated is diblock copolymer polystyrene–poly(ethylene oxide) having molecular mass 1.656 × 104 g/mol and blocks ratio 1 : 2. The micellization behavior is explored through 1H‐NMR, laser light scattering, light absorption, surface tension, and conductance and viscosity measurements. The results conclude that the critical micelles concentration of copolymer is 0.0951 g/dL at 25°C. It has been observed that the surface tension of solution decreases with the temperature and its impact is maxima in dilute concentration region. In addition, new methodologies have been introduced to get accurate critical micelles concentration and critical micelles temperature. © 2010 Wiley Periodicals, Inc., J Appl Polym Sci, 2010

Synthesis of monoclinic WO 3 nanosphere hydrogen gasochromic film via a sol–gel approach using PS- b-PAA diblock copolymer as template

A monoclinic tungsten trioxide (WO 3) nanosphere film was synthesized via a sol–gel approach using an amphiphilic diblock copolymer polystyrene- b-polyacrylic acid (PS- b-PAA) as template in toluene. The morphology, surface area and crystal structure of as-synthesized WO 3 were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET (N 2) and powder X-ray diffraction (XRD). The XRD pattern of WO 3 nanosphere film can be identified as a pure monoclinic WO 3 phase. The WO 3 precursor nanospheres had diameters ranging from 20 to 150 nm and surface area of 78.8 m 2 g −1. The hydrogen gasochromic experiments revealed that such WO 3 nanosphere film with high surface area had a rapid response (5 ∼ 10 s) to pure hydrogen at room temperature.

Synthesis of cationic amphiphilic diblock copolymers of poly(vinylbenzyl triethylammonium chloride) and polystyrene by reverse iodine transfer polymerization (RITP)

A new method called reverse iodine transfer polymerization (RITP), based on the in situ generation of transfer agents using molecular iodine I2, was applied to the synthesis of poly(vinylbenzyl chloride). Well-defined diblock copolymers poly(vinylbenzyl chloride)-b-polystyrene with different chain lengths were then successfully produced through sequential polymerization of styrene. The polydispersity index values Mw/Mn ranged from 1.4 to 1.6 for all the homopolymers and diblock copolymers. The diblock copolymers could be synthesized with equally good results by starting with either poly(vinylbenzyl chloride) or polystyrene as macrotransfer agents. The diblock copolymers were then quaternized with triethylamine to prepare cationic amphiphilic diblock copolymers.

Polymethylene‐b‐polystyrene diblock copolymer: Synthesis, property, and application

AbstractThe design and synthesis of well‐defined polymethylene‐b‐polystyrene (PM‐b‐PS, Mn = 1.3 × 104–3.0 × 104 g/mol; Mw/Mn (GPC) = 1.08–1.18) diblock copolymers by the combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) was successfully achieved. The 1H NMR spectrum and GPC traces of PM‐b‐PS indicated the successful extension of PS segment on the PM macroinitiator. The micellization behavior of such diblock copolymers in tetrahydrofuran were characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM) techniques. The average aggregate sizes of PM‐b‐PS diblock copolymers with the same length of PM segment in tetrahydrofuran solution (1.0 mg mL−1) increases from 104.2 nm to 167.7 nm when the molecular weight of PS segment increases. The spherical precipitated aggregates of PM‐b‐PS diblock copolymers with an average diameter of 600 nm were observed by AFM. Honeycomb porous films with the average diameter of 3.0 μm and 6.0 μm, respectively, were successfully fabricated using the solution of PM‐b‐PS diblock copolymers in carbon disulfide via the breath‐figure (BF) method under a static humid condition. The cross‐sections of low density polyethylene (LDPE)/polystyrene (PS)/PM‐b‐PS and LDPE/polycarbonate (PC)/PM‐b‐PS blends were observed by scanning electron microscope and reveal that the PM‐b‐PS diblock copolymers are effective compatilizers for LDPE/PS and LDPE/PC blends. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1894–1900, 2010

Strongly segregated cubic microdomain morphology consistent with the double gyroid phase in high molecular weight diblock copolymers of polystyrene and poly(dimethylsiloxane)

AbstractWe report the observation of a cubic phase consistent with the double gyroid structure in strongly segregated diblock copolymers of PS‐b‐PDMS over a volume fraction (φPDMS) range of ∼0.39 to 0.45. The samples have respective molecular weights of 127 kg/mol and 73 kg/mol and degree of segregation Nχ equal to 187 and 106, respectively, at annealing temperature of 130 °C. It is important to highlight that two out of the total four samples investigated, exhibited hexagonally close packed cylindrical domains of PDMS and alternating lamellae at φPDMS = 0.39 and 0.45, respectively, indicating the possible narrow range of the DG morphology for the specific diblock copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2419–2427, 2009

Large-Strain Mechanical Behavior of Model Block Copolymer Adhesives

Pressure-sensitive adhesives represent one of the most important commercial applications of block copolymers. The large-strain tensile properties of these soft adhesive materials play a dominant role in determining their adhesive properties. In many cases changes in the polymer architecture significantly affect the large-strain properties and the resultant adhesive performance, with little or no effect on the linear viscoelastic properties. In this Perspective we provide several examples, using model systems based on diblock, triblock, tetrablock, and star-block copolymers of polystyrene and polyisoprene.

Two dimensional nano-dot array engineering of block copolymer surface micelles on water surface

When an amphiphilic block copolymer is directly spread from an organic solution, the morphology of the surface micelles is not in general controlled because the structure is rapidly frozen after the solvent evaporation. In contrast, we have developed a new versatile method to generate highly regular ordered nanopatterns of the surface micelles on water, which involves the process of two dimensional (2D) hybridization with a polar liquid crystal molecule, 4′-pentyl-4-cyanobiphenyl (5CB) [Langmuir 22 (2006) 5233]. The present work extends this approach using a family of diblock copolymers of polystyrene- block-poly(4-vinylpyridine) changing the chain length of the two polymer blocks. It is found here that the dot-to-dot distance and the dot size can be precisely controlled on-demand by the length of the polymer blocks. Such structural regulations cannot be attained without the 5CB hybridization. Due to the high reproducibility of the morphology formation, this process should be of practical significance to ‘engineer’ the 2D patterns in the range of some tens of nanometers.

C60 fullerene inclusions in low-molecular-weight polystyrene–poly(dimethylsiloxane) diblock copolymers

Abstract We have synthesized low-molecular-weight diblock copolymers of polystyrene- block -poly(dimethylsiloxane) with total molecular weights 60 added. The C 60 was shown to selectively segregate into the PS phase only although its solubility limit is ∼1 wt%. Although the C 60 aggregates above 1 wt%, the cylindrical morphology observed in the pure copolymer bulk samples persists in the C 60 -copolymer composites even up to 10 wt% C 60 loading. In thin films, the pure copolymer possesses a highly ordered morphology with grains hundreds of microns across. When C 60 is blended with the copolymer the high degree of order rapidly decreases due to increasing numbers of defects observed.

Lamella reorientation in thin films of a symmetric poly(l-lactic acid)-block-polystyrene upon crystallization at different temperatures

The thin films of a symmetric crystalline-coil diblock copolymer of poly(l-lactic acid) and polystyrene (PLLA-b-PS) formed lamellae parallel to the substrate surface in melt. When annealed at temperatures well above the glass transition temperature of PLLA block (TgPLLA), the PLLA chains started to crystallize, leading to reorientation of lamellae. Such reorientation behavior exhibited dependence on the correlation between the crystallization temperature (Tc), the glass transition temperature of PS (TgPS), the peak melting point of PLLA crystals (TmPLLA), and the end melting point of PLLA crystals (Tm,endPLLA). When annealed at (Tc=) 80°C (Tc<TgPS<TODT, order–disorder transition temperature), 123°C (TgPS<Tc<TmPLLA<TODT), 165°C (TgPS<TmPLLA<Tc<Tm,endPLLA<TODT), the parallel lamellae became perpendicular to the substrate surface, exclusively starting at the edge of surface relief patterns. Meanwhile, the corresponding lamellar spacing was significantly enhanced. The PLLA crystallization between PS layers was hypothesized to account for the lamella reorientation during annealing. The crystallization, chain conformation, and possible chain folding mechanisms were discussed, based on detailed analysis of the lamellar structure before and after crystallization.

Fabrication of robust honeycomb polymer films: A facile photochemical cross-linking process

Highly ordered honeycomb films are prepared by breath-figure method using an amphiphilic diblock copolymer of polystyrene- block-polyacrylic acid (PS- b-PAA). By simply cross-linking PS matrix via deep ultraviolet (UV) irradiation, both the solvent and thermal stability of the porous films was significantly improved while retaining the three-dimensional (3D) structures. The film surface wettability was changed from hydrophobicity to hydrophilicity by the formed polar groups during the photochemical process. After 6 h UV cross-linking, the honeycomb structures could be preserved up to 320 °C, an increase of more than 200 K as compared to the non-cross-linked films.

Ultra-Large-Pore Mesoporous Carbons Templated from Poly(ethylene oxide)-b-Polystyrene Diblock Copolymer by Adding Polystyrene Homopolymer as a Pore Expander

A pore swelling approach was developed for the synthesis of ultralarge mesoporous carbons by using diblock copolymer PEO125-b-PS230 as a template, homopolystyrene (h-PS49) as a pore expander, resol as a carbon source, and THF as a solvent through solvent evaporation induced self-assembly (EISA). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) characterizations show that when h-PS94 amount is lower than 20 wt% relative to PEO125-b-PS230, highly ordered face-center cubic (fcc) mesoporous carbon structure (space group Fm3m) with ultralarge cell parameter of 46.4−58.0 nm can be obtained. Nitrogen sorption measurements reveal that the obtained LP-FDU-18s possess high surface area of about 1210 m2/g and large pore volume of 1.10 cm3/g. Because of adding pore swelling agent h-PS49, the mesostructural shrinkage is restrained, the pore wall thickness becomes very thin (3.6 nm). With the increase of h-PS49 addition amount from 0 to 20 wt%, the pore size can be continuously tuned in t...

PH-Dependent Self-Assembly of Polystyrene-block-Poly((sulfamate-carboxylate)isoprene) Copolymer in Aqueous Media

The amphiphilic polystyrene- block-poly((sulfamate-carboxylate)isoprene) (PS-PISC) diblock copolymer was synthesized from the precursor diblock copolymer polystyrene- block-isoprene by reaction with chlorosulfonyl isocyanate. The structure and behavior of self-assembled PS-PISC nanoparticles was studied in alkaline and acidic aqueous solutions by a combination of static and dynamic light scattering, analytical ultracentrifugation, atomic force and cryogenic transmission electron microscopies, NMR spectroscopy, potentiometric titration, and fluorometry using pyrene as a polarity-sensitive fluorescent probe. It was found that PS-PISC exists in aqueous solutions in the form of micellar aggregates. The aggregation tendency increases with decreasing effective charge density in the shell, that is, with decreasing pH of the solution, and aggregates found in alkaline aqueous media have much smaller molar masses than those formed in acidic media. The latter are dense, collapsed structures with immobile PISC domains in which most of the COOH and NH 2 (+)SO 3 (-) groups are buried inside of the nanoparticles. The swelling of PISC domains and disentanglement of PISC chains after addition of a base are slow processes occurring on the time scale of days.

Synthesis and self‐assembly of poly(styrene)‐b‐poly(N‐vinylpyrrolidone) amphiphilic diblock copolymers made via a combined ATRP and MADIX approach

AbstractAmphiphilic diblock copolymers of polystyrene (PS) and poly(N‐vinylpyrrolidone) (PNVP) were prepared by a combination of ATRP and MADIX. Well‐defined PS with bromine end group was synthesized by ATRP in bulk at 110 °C using (1‐bromoethyl) benzene as an initiator. The Br‐ end group was then converted to xanthate as verified by 1H NMR spectroscopy, elemental analysis, and UV‐spectroscopy. PS‐b‐PNVP copolymers were produced by MADIX of NVP in bulk at 60 °C using PS‐xanthate as a macro‐chain transfer agent and the kinetics of polymerization were investigated. The structures of PS‐b‐PNVP were characterized using GPC and 1H NMR. Amphiphilic PS‐b‐PNVP could form spherical micelles with PS cores and PNVP shells in aqueous solution as confirmed by 1H NMR and laser light scattering (LLS). The values of critical micelle concentration of PS‐b‐PNVP and the average aggregation number of PS‐b‐PNVP in the micelles were measured using pyrene as a probe and static LLS, respectively. The aggregation number increases concomitantly with temperature (10–50 °C), but the hydrodynamic radius of the micelles remains almost constant over the same temperature range, which may indicate shell dehydration at a higher temperature. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5604–5615, 2008

PH Response of Model Diblock and Triblock Copolymer Networks Containing Polystyrene and Poly(2-hydroxyethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate)

We investigated the swelling behavior of lamella-forming diblock and triblock copolymers of polystyrene, PS, and poly(2-hydroxyethyl methacrylate-co-2-(dimethylamino)ethyl methacrylate), PHD, with varying 2-(dimethylamino)ethyl methacrylate (DMAEMA) content. In phosphate buffer solutions of varying pH’s, these model networks swell like cationic hydrogels; their swelling characteristics are tunable through the DMAEMA content within the PHD block. While glassy PS domains within PS/PHD/PS can serve as physical cross-links in triblock copolymer networks, the PS domains are not effective anchors in diblock copolymer networks. PS/PHD with high DMAEMA content thus macroscopically disintegrate upon protonation of DMAEMA. The lamellar microdomains within these networks, however, continue to swell with decreasing pH. By reducing the DMAEMA content in PS/PHD, we have been able to create a diblock copolymer network that is macroscopically stable upon protonation of DMAEMA, as its water uptake cannot induce sufficient...

Direct Preparation of High Surface Area Mesoporous SiC-Based Ceramic by Pyrolysis of a Self-Assembled Polycarbosilane-block-Polystyrene Diblock Copolymer

Direct pyrolysis of a self-assembled inorganic−organic block copolymer can be a promising route for fabricating the ordered ceramic nanostructures based on the achievements of organic−organic block copolymers. Here we report the synthesis of a novel polycarbosilane-block-polystyrene diblock copolymer by ring-opening living anionic polymerization in a THF and n-hexane solvent system at −48 °C. The resulting block copolymer revealed phase-separation behavior in the nanoscale to form a self-assembled nanostructure that was converted to a mesoporous ceramic phase after heating at 800 °C. The pyrolyzed ceramic product exhibited well-ordered mesoporous SiC-based ceramic structures with a high BET surface area of 1325 m2 g−1 and an average mesopore size of 7.8 nm containing a large amount of micropores.