PS Segments Research Articles

Synthesis and characterization of novel dumbbell shaped copolymers poly(ethylene oxide)x-b-polystyrene-b-poly(ethylene oxide)x with tunable side arms by combination of efficient thiol-ene addition reaction with living polymerization mechanism

A series of well-defined dumbbell shaped copolymers consisting of PEO and PS segments were successfully synthesized by LAP and ROP mechanisms and the efficient thiol-ene addition reaction. This versatile synthetic route might be used to synthesize other similar copolymers.

Nanoporous Nonwoven Fibril-Like Morphology by Cooperative Self-Assembly of Poly(ethylene oxide)-block-Poly(ethyl acrylate)-block-Polystyrene and Phenolic Resin

Cooperative self-assembly of block copolymers with (in)organic precursors effectively generates ordered nanoporous films, but the porosity is typically limited by the need for a continuous (in)organic phase. Here, a network of homogeneous fibrous nanostructures (≈20 nm diameter cylinders) having high porosity (≈ 60%) is fabricated by cooperative self-assembly of a phenolic resin oligomer (resol) with a novel, nonfrustrated, ABC amphiphilic triblock copolymer template, poly(ethylene oxide)-block-poly(ethyl acrylate)-block-polystyrene (PEO-b-PEA-b-PS), via a thermally induced self-assembly process. Due to the high glass transition temperature (Tg) of the PS segments, the self-assembly behavior is kinetically hindered as a result of competing effects associated with the ordering of the self-assembled system and the cross-linking of resol that suppresses segmental mobility. The balance in these competing processes reproducibly yields a disordered fibril network with a uniform fibril diameter. This nonequilibrium morphology is dependent on the PEO-b-PEA-b-PS to resol ratio with an evolution from a relatively open fibrous structure to an apparent poorly ordered mixed lamellae-cylinder morphology. Pyrolysis of these former films at elevated temperatures yields a highly porous carbon film with the fibril morphology preserved through the carbonization process. These results illustrate a simple method to fabricate thin films and coatings with a well-defined fiber network that could be promising materials for energy and separation applications.

Temperature dependent charge transport in poly(3-hexylthiophene)-block polystyrene copolymer field-effect transistor

Electronic transport of regioregular poly(3-hexylthiophene)-block-poly styrene (rr-P3HT-b-PS) copolymer in field effect transistor (FET) geometry with different surface treatment and different temperature is investigated. The devices show p type behavior with a maximum saturation mobility of 6×10−3cm2/Vs and current on/off ratio of 2.6×104 in an OTS treated sample at room temperature, which is lower compared to the controlled P3HT sample of same molecular weight fabricated with the same surface treatment. The mobility measured at different temperatures (300–150K) show thermally activated hopping type transport mechanism with gate bias dependent activation energy of 100–270meV which is higher compared to the reported value of pristine P3HT FET. The higher activation energy in hopping behavior and lower mobility in this block copolymer is caused by insulating PS segments.

Core extractable nano-objects: Manipulating triblock copolymer micelles

We report manipulation of polymer nano-objects by changing solvents through chemically crosslinking the spherical micelles of poly(3-(triethoxysilyl)propyl methacrylate)-block-polystyrene-block-poly(2-vinylpyridine) (PTEPM-b-PS-b-P2VP). In methanol, which is a common solvent of PTEPM and P2VP but poor of PS, PTEPM-b-PS-b-P2VP forms micelles with a PS core. When changing the medium into acidic water, the PTEPM segments further collapse and gelate to form a crosslinked shell outside of the PS core. When the particles are re-dispersed into tetrahydrofuran (THF), the PS segments are extracted out, producing uniform small cavity of few nanometers in each particle. Thus one sample can be used to generate well-defined nano-objects with different appearance by solvent manipulation. The particle structure development has been characterized by transmission electron microscope (TEM), DLS, and 1H NMR. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Temperature‐induced Molecular Chain Motions of Styrenic Triblock Copolymers Studied by Intrinsic Fluorescence Spectra

AbstractThe temperature‐induced molecular chain motions of styrenic triblock copolymers (SBC), i.e. polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) and polystyrene‐block‐poly(ethylene‐co‐1‐butene)‐block‐polystyrene (SEBS), were studied by intrinsic fluorescence method. For SBS, the glass transition temperatures (Tgs) of B block and S block obtained by intrinsic fluorescence method were in good agreement with differential scanning calorimetry measurements (DSC). In the case of SEBS, an isoemission point was observed at about 310 nm at elevated temperatures, suggesting the slight conversion between the monomer and excimer emission. On this basis, the molecular chain motion of SEBS was monitored by both fluorescence intensity and excimer/monomer fluorescence ratio. Besides the Tgs of S block and EB blocks, a melting point (Tm) of weak crystalline in EB block was unambiguously determined by intrinsic fluorescence. Furthermore, it was found that the melting process directly led to the slight loosening of PS segments in interface and consequently the reduction of the amount of excimer. A reasonable mechanism was proposed to describe the molecular chain movements and phase transitions of SEBS upon heating. Moreover, the influence of temperature on the apparent activation energy of non‐radiative process (EaT) around Tg of S block was much stronger than that around Tg of B or EB blocks.

Tunable Arrangement of Gold Nanoparticles in Epoxidated Poly(styrene‐block‐butadiene) Diblock Copolymer Matrices

AbstractA new approach to synthesize block‐copolymer‐mediated/gold nanoparticle (Au NP) composites is developed. Stable and narrowly distributed Au NPs modified with a 2‐phenylethanethiol ligand are prepared by a two‐phase liquid–liquid method. A new epoxidation of a poly(styrene‐block‐butadiene) diblock copolymer, to form poly(styrene‐block‐vinyl oxirane) (PS‐b‐PBO), is achieved through chemical modification. It is found that the Au NPs disperse well in the PS block segment by partially crosslinking the PBO block segment with poly(ethylene oxide bisamine) (D230), a curing agent. The aggregation of Au NPs leads to a red‐shift of the plasmon absorption with the increase in the D230 content. However, without crosslinking the PBO block segment with D230, Au NPs distributes in both the PS and PBO segments.

Synthesis and photoluminescence properties of poly(2-methoxy-5-(2’-ethylhexyloxy)-p-phenylene vinylene-co-styrene) copolymers

A series of conjugated and non-conjugated copolymers of poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene-co-styrene) were synthesized via a typical chlorine precursor route. The obtained copolymers were characterized by FTIR spectra, UV-Vis spectra, 1H NMR and GPC. The results obtained indicated that the introduction of non-conjugated PS segments in MEH-PPV led to the interruption of conjugation structure and shortened the effective conjugated length, by which the optical properties of the conjugated polymer can be adjusted.

Intrinsic Fluorescence Studies of Conformational Relaxation and Its Dynamics of Triblock Copolymer during the Micellization in Selective Solvents

The aggregation behaviors of an ABA block copolymer, polystyrene-b-poly(ethylene/butylene)-b-polystyrene triblock copolymer (SEBS), were investigated in methylene dichloride (selective solvent for PS block) and mixture of n-hexane and cyclohexane (selective solvent of PEB block), i.e., SEBS-(S) and SEBS-(EB) solution, respectively. Both static and dynamic light scattering showed that the conformational change of molecular chain underwent three stages in SEBS-(S) solution. By using steady-state and time-resolved fluorescence, it was concluded that, when the micellization process of SEBS-(S) solution occurred, PS segments was dramatically stretched during the aggregation of PEB block into micelle cores, resulting in the great decrease in the amount of intramolecular excimers. In the case of SEBS-(EB) solution, five stages were observed in dynamic light scattering result during the micellization, suggesting that further aggregation between micelles was induced by the bridging effect of the dangling outer blo...

Synthesis and self-assembly of miktoarm star copolymers of (polyethylene)2−(polystyrene)2

We report on the synthesis and self-assembly of a novel well-defined miktoarm star copolymer of (polyethylene)2−(polystyrene)2, (PE)2−(PS)2, with two linear crystalline PE segments and two PS segments as the building blocks based on chain shuttling ethylene polymerization (CSEP), click reaction and atom transfer radical polymerization (ATRP). Initially, alkynyl-terminated PE (PE–) was synthesized via the esterification of pentynoic acid with hydroxyl-terminated PE (PE−OH), which was prepared using CSEP with 2,6-bis[1-(2,6-dimethylphenyl) imino ethyl] pyridine iron (II) dichloride/methylaluminoxane/diethyl zinc and subsequent in situ oxidation with oxygen. (PE)2−(OH)2 was then obtained by the click reaction of PE– with diazido and dihydroxyl containing coupling agent. The two hydroxyl groups in (PE)2−(OH)2 were then converted into bromisobutyrate by esterification. At last, the (PE)2−(PS)2 miktoarm star copolymers were synthesized by ATRP of styrene initiated from (PE)2−Br2 macroinitiator. All the intermediates and final products were characterized by 1H NMR and gel permeation chromatography (GPC). The self-assembly behavior was studied by dynamic light scattering (DLS) and atomic force microscopy (AFM). The crystallization of the (PE)2−(PS)2 miktoarm star copolymers was studied by differential scanning calorimetry (DSC).

Synthesis and Characterization of PDMS-, PVP-, and PS-Containing ABCBA Pentablock Copolymers

Amphiphilic ABCBA pentablock copolymers based on PVP, PS, and PDMS were synthesized using a combination of ATRP and RAFT polymerizations. The PVP-block-PS-block-PDMS-block-PS-block-PVP pentablock copolymer was characterized using a variety of chromatography and spectroscopic methods which showed that a high degree of end group and molecular weight control can be achieved. Preliminary analysis of the aqueous solution behavior of the pentablock copolymer showed that it self-assembles in water in order to shield the PDMS and PS segments from the water.

Synthesis of SiO2/polystyrene hybrid particles via an esterification method

SiO2/polystyrene (SiO2/PS) hybrid particles are synthesized successfully by an esterification method under extremely mild conditions, for instance, ambient temperature, moisture, and atmospheric pressure. The resulting hybrid particles are characterized by XPS, FTIR, SEM, DLS, TGA, and DSC techniques. Results show that the resulting hybrid particles have core-shell structure with PS on the outside and SiO2 in the core, and the particle size increases from 230 to 260 nm upon the PS grafting. The grafted PS accounts for about 32.2 wt.% of the total amount of hybrid particles. Meanwhile, PS segments attached on the SiO2 particle surface have better thermal stability and higher glass transition temperature than those of the pristine carboxyl-terminated PS.

Synthesis and Spectroscopic Studies of Macrocyclic Polystyrene Containing Two Fluorene Units and Single 9,10-Anthracenylidene Group

The synthesis of narrow distribution model macrocyclic polystyrenes initiated with 1,4-dipotassio-bis-1,4-(9′,9′-dimethyl-2′-fluorenyl)butane (DMFB) containing 12 to 55 styrene units and coupled to a single 9,10-anthracenylidene (AN) unit (PS-DMFB-AN) is reported. The initiator is formed via electron transfer/coupling from potassium naphthalenide to give nearly pure DMFB, followed by the addition of styrene and protonation or intramolecular end-to-end coupling with 9,10-bis(chloromethyl)anthracene to give the linear and cyclic polymers, respectively. Forster transfer from the 9,9-dimethyl-2-fluorenyl (DMF) group donors to the AN groups, surprisingly, only slightly increased with lower degrees of polymerization of the PS segments. Extensive simulations indicate the presence of highly asymmetrical polymers in which the two arms of the polymer dianion significantly differ in the degree of polymerization. This appears to be partially due to chain statistics but also to slow initiation relative to polymerization.

Solid-State NMR Studies of Structures and Molecular Motions for the Spidroin-Like Polymers

Using 13C solid-state nuclear magnetic resonance(NMR) we studied the structures of two spidroin-like polymers which were synthesized by the polymerization of polyalanine ((Ala)5) with oligomers of polystyrene(PS, MW=2000) and polyisoprene(PI, MW=2210). 13C CP/MAS (cross polarization/magic angle spinning) NMR spectra and spin-lattice relaxation time in the rotating frame (T1ρ(13C)) results of the polymers indicated that the chemical shifts of (Ala)5 in both polymers of polystyrene-co-polyalanine (PS-co-PAL) and polyisoprene-co-polyalanine (PI-co-PAL) were almost the same. This means that (Ala)5 peptide segments in the two polymers have similar chemical environments and secondary structures. The similar T1ρ(13C) values for (Ala)5 in the two polymers indicate that (Ala)5 peptide segments also have similar aggregate structures. The mechanical properties of the two spidroin-like polymers are quite different: PS-co-PAL is granular and tough while PI-co-PAL is rubber-like and tensible at room temperature. This indicates that the mechanical performances of spidroin-like polymers are strongly linked to the properties of the chosen polymers. The T1ρ(13C) values of the skeletons —CH2CH— in PI-co-PAL and PS-co-PAL were (5.3±0.4) and (47.0±5.5) ms, respectively, which indicates that PI segments are softer than PS segments in the polymers. In addition, the density functimal theory (DFT) based chemical shift calculation showed that (Ala)5 peptide segments in the polymers of PS- co-PAL and PI-co-PAL had dihedral angles of (-131°, 142°), which correspond to a β-sheet conformation.

Star polystyrene‐b‐hyperbranched polyglycidol: Synthesis and ionic conductivity

AbstractIn this work, novel star‐hyperbranched block copolymers containing four polystyrene arms and hyperbranched polyglycidol at the end of each arm (sPS‐b‐HPG) have been synthesized. The polystyrene arms were prepared through atom transfer radical polymerization of styrene starting from a four‐arm initiator. The hydroxyl‐terminated PS star polymers served as precursors for the cationic ring‐opening polymerization of glycidol using BF3·OEt2 as the catalyst. The chemical structures of these block copolymers were characterized by using 1H and 13C NMR. DSC analysis indicated that the star‐hyperbranched block copolymers exhibited two distinct glass transition temperatures corresponding to the linear PS and the HPG segments, respectively. The addition of LiClO4 increased the Tg of HPG segments at low concentrations, however, decreased the Tg at high concentrations. The Tg of PS segments was not affected by the addition of salts at all. Furthermore, the interaction of sPS‐b‐HPG with LiBr was studied by using viscosity analysis based on the Jones–Dole equation. The star‐like PS core strengthened the interaction of sPS‐b‐HPG with Li ions that could facile the inhomogeneous distribution of Li cations and anions in different phases, which is important in polymeric electrolytes for lithium chemical power sources. The ionic conductivity of one sPS‐b‐HPG/LiClO4 electrolyte was measured to be higher than that of HPG/LiClO4 electrolyte. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 949–958, 2009

Synthesis of inverse star block copolymer by combination of ATRP, ring opening polymerization, and “click chemistry”

AbstractThe inverse star block copolymer, (poly(ε‐caprolactone)‐b‐polystyrene)2‐core‐(poly(ε‐caprolactone)‐b‐polystyrene)2, [(PCL‐PS)2‐core‐(PCL‐PS)2] has been successfully prepared by combination of atom transfer radical polymerization (ATRP), ring opening polymerization (ROP), and “Click Chemistry.” The synthesis includes the following five steps: (1) synthesis of a heterofunctional initiator with two ATRP initiating groups and two hydroxyl groups; (2) formation of (Br‐PS)2‐core‐(OH)2 via ATRP of styrene; (3) preparation of the (PCL‐PS)2‐core‐(OH)2 through “click” reaction of the α‐propargyl, ω‐acetyl terminated PCL with (N3‐PS)2‐core‐(OH)2 which was prepared by transformation of the terminal bromine groups in (Br‐PS)2‐core‐(OH)2 into azide groups; (4) the ROP of CL using (PCL‐PS)2‐core‐(OH)2 as macroinitiator to form (PCL‐PS)2‐core‐(PCL‐OH)2; and (5) preparation of the (PCL‐PS)2‐core‐(PCL‐PS)2 through the ATRP of styrene using (PCL‐PS)2‐core‐(PCL‐Br)2 as macroinitiator which was prepared by reaction of the terminal hydroxyl groups at the end of the PCL chains with 2‐bromoisobutyryl bromide. The characterization data support structures of the inverse star block copolymer and the intermediates. The differential scanning calorimeter results and polarized optical microscope observation showed that the intricate structure of the inverse star block copolymer greatly restricted the movement of the PS segments and PCL segments, resulted in the increase of the glass transition temperature of PS segments and the decrease of crystallization ability of PCL segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7757–7772, 2008

Nitroxide‐mediated synthesis of styrenic‐based segmented and tapered block copolymers using poly(lactide)‐functionalized TEMPO macromediators

AbstractPoly(styrene)‐poly(lactide) (PS‐PLA), poly (tert‐butyl styrene)‐poly(lactide) (PtBuS‐PLA) diblocks, and poly(tert‐butyl styrene)‐poly(styrene)‐poly(lactide) (PtBuS‐PS‐PLA) segmented and tapered triblocks of controlled segment lengths were synthesized using nitroxide‐mediated controlled radical polymerization. Well‐defined PLA‐functionalized macromediators derived from hydroxyl terminated TEMPO (PLAT) of various molecular weights mediated polymerizations of the styrenic monomers in bulk and in dimethylformamide (DMF) solution at 120–130°C. PS‐PLA and PtBuS‐PLA diblocks were characterized by narrow molecular weight distributions (polydispersity index (Mw/Mn) < 1.3) when using the PLATmediator with the lowest number average molecular weightMn= 6.1 kg/mol while broader molecular weight distributions were exhibited (Mw/Mn= 1.47‐1.65) when using higher molecular weight mediators (Mn= 7.4 kg/mol and 11.3 kg/mol). Segmented PtBuS‐PS‐PLA triblocks were initiated cleanly from PtBuS‐PLA diblocks although polymerizations were very rapid with PS segments ∼ 5–10 kg/mol added within 3–10 min of polymerization at 130°C in 50 wt % DMF solution. Tapering from the PtBuS to the PS segment in semibatch mode at a lower temperature of 120°C and in 50 wt % DMF solution was effective in incorporating a short random segment of PtBuS‐ran‐PS while maintaining a relatively narrow monomodal molecular weight distribution (Mw/Mn≈ 1.5). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

A Novel GPPS/cis‐SB Blend with High Performance

AbstractSummary: GPPS/cis‐SB blends with high performance were prepared by adding 3–5 wt.‐% stereoregular butadiene‐styrene block copolymers (cis‐SB) with a high cis‐1,4 configuration of around 97% into general purpose polystyrene (GPPS). The micromorphology of the GPPS/cis‐SB blends was characterized by transmission electron microscopy (TEM). Mechanical properties including tensile and impact properties were studied and the fracture surfaces of tensile and impact test specimens were characterized by scanning electron microscopy (SEM). PB domains of 10–30 nm with a blurry interface were tethered by continuous PS domains. The fracture surface of the tensile test piece of GPPS was relatively smooth while the fractography of patch patterns separated by river patterns was formed when the tensile specimens of GPPS/cis‐SB blends were broken, which may be due to the nanometer‐scale rubber phases with high cis‐1,4 configuration and some partially crystalline PS segments in the cis‐SB block copolymer. It is found that GPPS could be greatly toughened by introduction of a small amount of cis‐SB and the tensile strength and elongation at break could also be increased.

A Novel Route for the Preparation of Discrete Nanostructured Carbons from Block Copolymers with Polystyrene Segments

AbstractWell‐defined nanostructured carbon was prepared by pyrolysis of core cross‐linked micelles formed from block copolymers containing polystyrene segments. These micelles were obtained by self‐assembly of poly(ethylene oxide)‐block‐polystyrene (PEO113‐b‐PS52) diblock copolymer or brush macromolecules containing polymethacrylate backbone and side chains with PS and poly(acrylic acid) block segments (PBPEM330‐g‐PS40‐b‐PAA111) in selective solvents. UV irradiation was used to induce cross‐linking of the PS core in the micelles. After pyrolysis, the cross‐linked PS cores were converted to a partially graphitic carbon, while the shells were sacrificed, resulting in the formation of discrete carbon nano‐objects. The formation of carbon material was confirmed by Raman scattering spectroscopy while the morphology of the precursor and the resulting pyrolyzed product was studied by atomic force microscope (AFM).magnified image

Synthesis of efficient and reusable palladium catalyst supported on pH-responsive colloid and its application to Suzuki and Heck reactions in water

An efficient and reusable pH-responsive colloid supported palladium catalyst was synthesized by loading 3-nm Pd nanoparticles into the pH-responsive colloid of core–shell microspheres of poly[styrene- co-2-(acetoacetoxy)ethyl methacrylate- co-methyl acrylic acid] (PS- co-PAEMA- co-PMAA). The colloidal scaffold of the core–shell microspheres, which contained a pH-responsive shell of PMAA segment and a coordinative core of PAEMA and PS segments, was synthesized by one-stage soap-free emulsion polymerization in water. The pH-responsive colloid supported palladium catalyst was dispersed in basic aqueous medium like a homogeneous catalyst, and also could be simply separated and recovered like a heterogeneous one just by adjusting pH of the aqueous medium. The pH-responsive colloid-supported palladium catalyst proved to be efficient and reusable for the Suzuki and Heck reactions performed in water.

Templating of Gold Nanocrystals in Micellar Cores of Block Copolymer Films

Thin film functional hybrid materials composed of inorganic nanocrystals sequestered within a self-assembled template are important for a diverse range of applications, from sensors to device electronics. The properties of these materials can be “tailored” by control of composition over various length scales; the major processing challenges are associated with understanding and controlling external factors, such as confinement and interfacial interactions, that affect the self-organization process. Spin-cast polystyrene-b-poly(1,1‘,2,2‘-tetrahydroperflurooctyl methacrylate) (PS-b-PFOMA) diblock copolymer films can form a micellar structure, with a PFOMA core (PS corona), and are induced to undergo a transition by annealing in supercritical CO2; consequently, the PS segments form the core with a PFOMA corona. We show that functionalized Au nanocrystals, initially dispersed within the corona (the PS phase) of the micelles, follow the morphological inversion and become sequestered within the core, now composed of PS chains; the nanoparticles segregate primarily at the PS/PFOMA interface within the core. These inversion experiments were performed on nanocomposite films with thicknesses h ≤ 150 nm. Therefore, only one or two layers of micelles spanned the entire film. The nanoparticles were not distributed uniformly throughout the films but remained primarily near the substrate. Several competing factors determine the overall distribution of nanoparticles: the van der Waals interaction between nanoparticles and interfaces, favorable ligand−block enthalpic interactions, and the conformational entropy of the host chains.