Incorporation of titanium dioxide particles into polymer matrix using block copolymer micelles for fabrication of high refractive and transparent organic–inorganic hybrid materials

We report a novel strategy for incorporation of titanium dioxide (TiO₂) particles into poly(methyl methacrylate) (PMMA) to exploit high refractive and transparent organic–inorganic hybrid materials. Formation of TiO₂ particles of around 20 nm was conducted within hydrophilic core of block copolymer micelles of poly(methyl methacrylate‐block‐acrylic acid) (PMMA‐b‐PAA) in toluene via sol–gel process from titanium isopropoxide and hydrochloric acid. Subsequently, incorporation of TiO₂ particles into PMMA matrix was carried out by casting toluene solution of TiO₂ precursor‐loaded copolymer micelles, prepared from PMMA₃₅₀‐b‐PAA₉₃ and the precursor of mole ratio Ti⁴⁺/carboxyl 4.0, and PMMA. Hybrid films of TiO₂/PMMA exhibited high transparency to achieve transmission over 87% at 500 nm at 30 wt % of TiO₂ content. The refractive index of resulting hybrid films at 633 nm linearly increased with TiO₂ content to attain 1.579 at 30 wt % TiO₂, which was 0.1 higher than that of PMMA. Cross‐sectional transmission electron microscope images of TiO₂/PMMA hybrid films showed existence of TiO₂ clusters less than 100 nm, which were probably formed by aggregation or agglutination of TiO₂ particles during a drying process. It was also observed that decomposition temperature of the hybrid films elevated with increasing TiO₂ content. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of coil‐comb block copolymers containing polystyrene coil and poly(methyl methacrylate) side chains via atom transfer radical polymerization

A series of polystyrene‐b‐(poly(2‐(2‐bromopropionyloxy) styrene)‐g‐poly(methyl methacrylate)) (PS‐b‐(PBPS‐g‐PMMA)) and polystyrene‐b‐(poly(2‐(2‐bromopropionyloxy)ethyl acrylate)‐g‐poly(methyl methacrylate)) (PS‐b‐(PBPEA‐g‐PMMA)) as new coil‐comb block copolymers (CCBCPs) were synthesized by atom transfer radical polymerization (ATRP). The linear diblock copolymer polystyrene‐b‐poly(4‐acetoxystyrene) and polystyrene‐b‐poly(2‐(trimethylsilyloxy)ethyl acrylate) PS‐b‐P(HEA‐TMS) were obtained by combining ATRP and activators regenerated by electron transfer (ARGET) ATRP. Secondary bromide‐initiating sites for ATRP were introduced by liberation of hydroxyl groups via deprotection and subsequent esterification reaction with 2‐bromopropionyl bromide. Grafting of PMMA onto either the PBPS block or the PBPEA block via ATRP yielded the desired PS‐b‐(PBPS‐g‐PMMA) or PS‐b‐(PBPEA‐g‐PMMA). ¹H nuclear magnetic resonance spectroscopy and gel permeation chromatography data indicated the target CCBCPs were successfully synthesized. Preliminary investigation on selected CCBCPs suggests that they can form ordered nanostructures via microphase separation. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2971–2983     

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization in ionic liquid

Polymerization‐induced self‐assembly of block copolymer through dispersion RAFT polymerization has been demonstrated to be a valid method to prepare block copolymer nano‐objects. However, volatile solvents are generally involved in this preparation. Herein, the in situ synthesis of block copolymer nano‐objects of poly(ethylene glycol)‐block‐polystyrene (PEG‐b‐PS) in the ionic liquid of 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIN][PF₆]) through the macro‐RAFT agent mediated dispersion polymerization is investigated. It is found that the dispersion RAFT polymerization of styrene in the ionic liquid of [BMIN][PF₆] runs faster than that in the alcoholic solvent, and the dispersion RAFT polymerization in the ionic liquid affords good control over the molecular weight and the molecular weight distribution of the PEG‐b‐PS diblock copolymer. The morphology of the in situ synthesized PEG‐b‐PS diblock copolymer nano‐objects, e.g., nanospheres and vesicles, in the ionic liquid is dependent on the polymerization degree of the solvophobic block and the concentration of the fed monomer, which is somewhat similar to those in alcoholic solvent. It is anticipated that the dispersion RAFT polymerization in ionic liquid broads a new way to prepare block copolymer nano‐objects. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1517–1525     

Synthesis of methyl methacrylate,styrene, and isobutylene multiblock copolymers using atom transfer and cationic polymerization

ABCBA‐type pentablock copolymers of methyl methacrylate, styrene, and isobutylene (IB) were prepared by the cationic polymerization of IB in the presence of the α,ω‐dichloro‐PS‐b‐PMMA‐b‐PS triblock copolymer [where PS is polystyrene and PMMA is poly(methyl methacrylate)] as a macroinitiator in conjunction with diethylaluminum chloride (Et₂AlCl) as a coinitiator. The macroinitiator was prepared by a two‐step copper‐based atom transfer radical polymerization (ATRP). The reaction temperature, ?78 or ?25 °C, significantly affected the IB content in the resulting copolymers; a higher content was obtained at ?78 °C. The formation of the PIB‐b‐PS‐b‐PMMA‐b‐PS‐b‐PIB copolymers (where PIB is polyisobutylene), prepared at ?25 (20.3 mol % IB) or ?78 °C (61.3 mol % IB; rubbery material), with relatively narrow molecular weight distributions provided direct evidence of the presence of labile chlorine atoms at both ends of the macroinitiator capable of initiation of cationic polymerization of IB. One glass‐transition temperature (T_g), 104.5 °C, was observed for the aforementioned triblock copolymer, and the pentablock copolymer containing 61.3 mol % IB showed two well‐defined T_g's: ?73.0 °C for PIB and 95.6 °C for the PS–PMMA blocks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3823–3830, 2005     

4‐hydroxythiophenol grafted PS‐b‐PAA block copolymers: Preparation and formation of porous and bowl‐shaped assemblies

4‐Hydroxythiophenol (HTP) grafted poly(styrene‐b‐acrylic acid) (PS‐b‐PAA) block copolymers (BCPs) (PS‐b‐PAA‐g‐HTP) was synthesized using the esterification reaction between the carboxyl groups and hydroxyl groups. Self‐assembly behavior of the graft copolymer in 1,4‐dioxane/water was investigated. Assemblies of different morphologies, porous, and bowl‐shaped structures, could be easily prepared. A possible mechanism for the formation of the porous and bowl‐shaped structures was discussed. The present study showed a facile method for the preparation of functionalized PS‐b‐PAA BCPs, which could easily self‐assembly into novel structures in aqueous solution. These assemblies may be used to generate new functional materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1551–1557     

Enhancing the PLA crystallization rate by incorporating a polystyrene‐block‐poly(methyl methacrylate) block copolymer: Synergy of polystyrene and poly(methyl methacrylate) segments

A polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) exhibiting a well‐defined structure was prepared combining anionic polymerization and mercaptan/ε‐caprolactam living polymerization. To evaluate how this block copolymer affected the crystallization of polylactide (PLA), 0.5 wt % thiol‐terminated PS homopolymer (PSSH), PMMA, and PS‐b‐PMMA was melt‐blended with PLA. The calorimetric characterization of the nonisothermal and isothermal crystallization behavior was analyzed according to Avrami's theory, indicating that PS‐b‐PMMA more effectively increased the crystallization kinetics of the PLA matrix than did PSSH or PMMA. The results revealed that the synergistic effect of the PS and PMMA blocks appeared only when they were simultaneously presented in the PLA matrix. The PS block increased the number of nucleation sites and decreased the spherulite size, whereas the PMMA block facilitated the excellent dispersion of PS‐b‐PMMA in the PLA matrix as shown in polarizing optical microscope experiments. Incorporating PS‐b‐PMMA improved the PLA crystallization rate by promoting heterogeneous nucleation. In addition, incorporating 0.5 wt % PS‐b‐PMMA increased the relative crystallinity of PLA to 43.5%, and decreased the crystallization half‐time to 2.4 min when the blend was isothermal at 105 °C. The PLA crystal structure was unchanged by the presence of PS‐b‐PMMA; however, the crystallization rate was enhanced as probed by SEM and X‐ray diffraction. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 823–832     

One‐pot synthesis of star‐block copolymers using double click reactions

3‐Arm star‐block copolymers, (polystyrene‐b‐poly(methyl methacrylate))₃, (PS‐b‐PMMA)₃, and (polystyrene‐b‐poly(ethylene glycol))₃, (PS‐b‐PEG)₃, are prepared using double‐click reactions: Huisgen and Diels–Alder, with a one‐pot technique. PS and PMMA blocks with α‐anthracene‐ω‐azide‐ and α‐maleimide‐end‐groups, respectively, are achieved using suitable initiators in ATRP of styrene and MMA, respectively. However, PEG obtained from a commercial source is reacted with 3‐acetyl‐N‐(2‐hydroxyethyl)‐7‐oxabicyclo[2.2.1]hept‐5‐ene‐2‐carboxamide (7) to give furan‐protected maleimide‐end‐functionalized PEG. Finally, PS/PMMA and PS/PEG blocks are linked efficiently with trialkyne functional linking agent 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane 2 in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) at 120 °C for 48 h to give two samples of 3‐arm star‐block copolymers. The results of the peak splitting using a Gaussian deconvolution of the obtained GPC traces for (PS‐b‐PMMA)₃ and (PS‐b‐PEG)₃ displayed that the yields of target 3‐arm star‐block copolymers were found to be 88 and 82%, respectively. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7091–7100, 2008     

Orientation control in nanoparticle filled block copolymer cold zone annealed films

Nanoparticles provide an attractive route to modifying polymer thin film properties, yet controlling the dispersion and morphology of functionalized nanoparticle filled films is often difficult. Block copolymers can provide an ideal template for directed assembly of nanoparticles under controlled nanoparticle‐polymer interactions. Previously we observed that neat films of cylinder forming poly(styrene‐b‐methyl methacrylate) PS‐b‐PMMA block copolymer (c‐BCP) orient vertically with dynamic sharp thermal cold zone annealing (CZA‐S) over wide range of CZA‐S speed (0.1–10) μm/s. Here, we introduce a low concentration (1–5 wt %) of nanoparticles of phenolic group functionalized CdS (fCdS‐NP), to PMMA cylinder forming polystyrene‐b‐poly (methyl methacrylate) block copolymer (c‐BCP) films. Addition of the fCdS‐NP induces a vertical to horizontal orientation transition at low CZA‐S speed, V = 5 μm/s. The orientation flip studies were analyzed using AFM and GISAXS. These results confirm generality of our previously observed orientation transition in c‐BCP under low speed CZA‐S with other nanoparticles (gold [Au‐NP], fulleropyrrolidine [NCPF‐NP]) in the same concentration range, but reveal new aspects not previously examined: (1) A novel observation of significant vertical order recovery from 5–10% vertical cylindrical fraction at V = 5 μm/s to 46–63% vertical cylindrical fraction occurring at high CZA‐S speed, V = 10 μm/s for the fCdS nanoparticle filled films. (2) We rule out the possibility that a nanoparticle wetting layer on the substrate is responsible for the vertical to horizontal flipping transition. (3) We demonstrate that the orientation flipping results can be achieved in a nanoparticle block copolymer system where the nanoparticles are apparently better‐dispersed within only one (matrix PS) domain unlike our previous nanoparticle system studied. We consider facile processing conditions to fabricate functionalized nanoparticles filled PS‐PMMA block copolymer films with controlled anisotropy, a useful strategy in the design of next generation electronic and photonic materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 604–614     

Synthesis and solvent‐dependent micellization of the amphiphilic block copolymer poly(styreneboronic acid)‐block‐polystyrene

The amphiphilic organoboron block copolymer poly (styreneboronic acid)‐block‐polystyrene ( PSBA‐b‐PS ) has been prepared through a postpolymerization modification route from the silicon‐functionalized block copolymer poly(4‐trimethylsilylstyrene)‐block‐polystyrene ( PSSi‐b‐PS ). PSBA‐b‐PS is obtained through highly selective reaction of PSSi‐b‐PS with BBr₃ at room temperature and subsequent hydrolysis of the BBr₂‐functionalized intermediate. Transmission electron microscopy studies demonstrate that PSBA‐b‐PS undergoes pH dependent micellization in aqueous solution. Different morphologies could be realized by using different mixtures of water and organic solvents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2438–2445, 2010     

Synthesis of H‐shaped complex macromolecular structures by combination of atom transfer radical polymerization,photoinduced radical coupling,ring‐opening polymerization,and iniferter processes

Three controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring‐opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD‐type H‐shaped complex copolymer. First, α‐benzophenone functional polystyrene (BP‐PS) and poly(methyl methacrylate) (BP‐PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene‐b‐poly(methyl methacrylate) (PS‐b‐PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of ε‐caprolactone (CL) by using PS‐b‐PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL‐PS‐PMMA‐PCL. Finally, the polymerization of tert‐butyl acrylate (tBA) via iniferter process gave the targeted H‐shaped block copolymer. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4601–4607     

Synthesis of poly(methyl methacrylate)‐b‐polystyrene containing a crown ether unit at the junction point via combination of atom transfer radical polymerization and nitroxide mediated radical polymerization routes

Poly(methyl methacrylate)‐b‐polystyrene (PMMA‐b‐PS) containing a benzo‐15‐crown‐5 unit at the junction point was prepared by combining atom transfer radical polymerization and nitroxide‐mediated radical polymerization. For this purpose, 6,7,9,10,12,13,15,16‐octahydro‐5,8,11,14,17‐pentaoxa‐benzocyclopentadecene‐2‐carboxylic acid 3‐(2‐bromo‐2‐methyl‐propionyloxy)‐2‐methyl‐2‐[2‐phenyl‐2‐(2,2,6,6‐tetramethyl‐piperidin‐1‐yloxy)‐ethoxycarbonyl]‐propyl ester ( 3 ) was synthesized and used as an initiator in atom transfer radical polymerization of methyl methacrylate in the presence of CuCl and pentamethyldiethylenetriamine at 60°C. A linear behavior was observed in both plots of ln([M]₀/[M]) versus time and M_n,_GPC versus conversion indicating that the polymerization proceeded in a controlled/living manner. Thus obtained PMMA precursor was used as a macroinitiator in nitroxide‐mediated radical polymerization of styrene (St) at 125°C to give well‐defined PMMA‐b‐PS with crown ether per chain. Kinetic data were also obtained for copolymerization. Moreover, potassium picrate (K⁺ picrate) complexation of 3 and PMMA‐b‐PS copolymer was studied. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3242–3249, 2006     

Block‐brush copolymers via ROMP and sequential double click reaction strategy

We report an efficient way, sequential double click reactions, for the preparation of brush copolymers with AB block‐brush architectures containing polyoxanorbornene (poly (ONB)) backbone and poly(ε‐caprolactone) (PCL), poly(methyl methacrylate) (PMMA) or poly(tert‐butyl acrylate) (PtBA) side chains: poly(ONB‐g‐PMMA)‐b‐poly(ONB‐g‐PCL) and poly(ONB‐g‐PtBA)‐b‐poly(ONB‐g‐PCL). The living ROMP of ONB affords the synthesis of well‐defined poly(ONB‐anthracene)₂₀‐b‐poly (ONB‐azide)₅ block copolymer with anthryl and azide pendant groups. Subsequently, well‐defined linear alkyne end‐functionalized PCL (PCL‐alkyne), maleimide end‐functionalized PMMA (PMMA‐MI) and PtBA‐MI were introduced onto the block copolymer via sequential azide‐alkyne and Diels‐Alder click reactions, thus yielding block‐brush copolymers. The molecular weight of block‐brush copolymers was measured via triple detection GPC (TD‐GPC) introducing the experimentally calculated dn/dc values to the software. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

“Click” synthesis of thermally stable au nanoparticles with highly grafted polymer shell and control of their behavior in polymer matrix

Thermally stable core–shell gold nanoparticles (Au NPs) with highly grafted polymer shells were synthesized by combining reversible addition‐fragmentation transfer (RAFT) polymerization and click chemistry of copper‐catalyzed azide‐alkyne cycloaddition (CuAAC). First, alkyne‐terminated poly(4‐benzylchloride‐b‐styrene) (alkyne‐PSCl‐b‐PS) was prepared from the alkyne‐terminated RAFT agent. Then, an alkyne‐PSCl‐b‐PS chain was coupled to azide‐functionalized Au NPs via the CuAAC reaction. Careful characterization using FT‐IR, UV–Vis, and TGA showed that PSCl‐b‐PS chains were successfully grafted onto the Au NP surface with high grafting density. Finally, azide groups were introduced to PSCl‐b‐PS chains on the Au NP surface to produce thermally stable Au NPs with crosslinkable polymer shell ( Au‐PSN₃‐b‐PS 1 ). As the control sample, PS‐b‐PSN₃‐coated Au NPs ( Au‐PSN₃‐b‐PS 2 ) were made by the conventional “grafting to” approach. The grafting density of polymer chains on Au‐PSN₃‐b‐PS 1 was found to be much higher than that on Au‐PSN₃‐b‐PS 2 . To demonstrate the importance of having the highly packed polymer shell on the nanoparticles, Au‐PSN₃‐b‐PS 1 particles were added into the PS and PS‐b‐poly(2‐vinylpyridine) matrix, respectively. Consequently, it was found that Au‐PSN₃‐b‐PS 1 nanoparticles were well dispersed in the PS matrix and PS‐b‐P2VP matrix without any aggregation even after annealing at 220 °C for 2 days. Our simple and powerful approach could be easily extended to design other core–shell inorganic nanoparticles. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Investigation of block depth distribution in PS‐b‐PMMA block copolymer using ultra‐low‐energy cesium sputtering in ToF‐SIMS

Directed self‐assembly of block copolymers (BCPs) is a promising candidate for next generation nanolithography. In order to validate a given pattern, the lateral and in‐depth distributions of the blocks should be well characterized; for the latter, time‐of‐flight (ToF) SIMS is a particularly well‐adapted technique. Here, we use an ION‐TOF ToF‐SIMS V in negative mode to provide qualitative information on the in‐depth organization of polystyrene‐b‐polymethylmethacrylate (PS‐b‐PMMA) BCP thin films. Using low‐energy Cs⁺ sputtering and Bi₃⁺ as the analysis ions, PS and PMMA homopolymer films are first analyzed in order to identify the characteristic secondary ions for each block. PS‐b‐PMMA BCPs are then characterized showing that self‐assembled nanodomains are clearly observed after annealing. We also demonstrate that the ToF‐SIMS technique is able to distinguish between the different morphologies of BCP investigated in this work (lamellae, spheres or cylinders). ToF‐SIMS characterization on BCP is in good agreement with XPS analysis performed on the same samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Graft copolymers via ROMP and Diels–Alder click reaction strategy

Anthracene‐functionalized oxanorbornene monomer and oxanorbornenyl polystyrene (PS) with ω‐anthracene end‐functionalized macromonomer were first polymerized via ring‐opening metathesis polymerization using the first‐generation Grubbs' catalyst in dichloromethane at room temperature and then clicked with maleimide end‐functionalized polymers, poly(ethylene glycol) (PEG)‐MI, poly(methyl methacrylate) (PMMA)‐MI, and poly(tert‐butyl acrylate) (PtBA)‐MI in a Diels–Alder reaction in toluene at 120 °C to create corresponding graft copolymers, poly(oxanorbornene)‐g‐PEG, poly(oxanorbornene)‐g‐PMMA, and graft block copolymers, poly(oxanorbornene)‐g‐(PS‐b‐PEG), poly(oxanorbornene)‐g‐(PS‐b‐PMMA), and poly(oxanorbornene)‐g‐(PS‐b‐PtBA), respectively. Diels–Alder click reaction efficiency for graft copolymerization was monitored by UV–vis spectroscopy. The dn/dc values of graft copolymers and graft block copolymers were experimentally obtained using a triple detection gel permeation chromatography and subsequently introduced to the software so as to give molecular weights, intrinsic viscosity ([η]) and hydrodynamic radius (R_h) values. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and self‐assembly of thermotropic block copolymer with long alkyl tethered cage silsesquioxane in the side chain

Thermotropic POSS‐containing poly(methacrylate) with long alkyl chain tethered polyhedral oligomeric silsesquioxane (POSS) in the side chain and the block copolymers (PMMA‐b‐PMAC11POSS) were developed by through living anionic polymerization. The resulting polymers indicated a phase transition temperature at 112 °C from spherocrystal to isotropic phase. The POSS‐containing polymer segments tended to form matrix of microphase‐separated nanostructures in the bulk even in the very low volume fraction, for instance, PMMA cylindrical nanostructure was obtained by PMMA₁₇₅‐b‐PMAC11POSS₁₁ (?_PMAC11POSS = 0.44). The control of thin film morphology was carried out by not only solvent annealing, but also thermal annealing, resulting in the formation of well‐ordered dot‐ and fingerprint‐type nanostructures. This is the first report in a series of POSS‐containing block polymers that are capable for thermal annealing to generate well‐ordered microphase‐separated nanostructures in thin films. The novel thermotropic POSS‐containing block copolymer offers a promising material for block copolymer lithography. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis,surface properties,and morphologies of poly[methyl(3,3,3‐trifluoropropyl)siloxane]‐b‐polystyrene‐b‐poly(tert‐butyl acrylate) triblock copolymers by a combination of anionic ROP and ATRP

A series of well‐defined poly[methyl(3,3,3‐trifluoropropyl)siloxane]‐b‐polystyrene‐b‐poly(tert‐butyl acrylate) (PMTFPS‐b‐PS‐b‐PtBA) triblock copolymers were prepared by a combination of anionic ring‐opening polymerization of 1,3,5‐trimethyl‐1,3,5‐tris(3′,3′,3′‐trifluoropropyl)cyclotrisiloxane (F₃), and atom transfer radical polymerization (ATRP) of styrene (St) and tert‐butyl acrylate (tBA), using the obtained α‐bromoisobutyryl‐terminal PMTFPS (PMTFPS‐Br) as the macroinitiators. The ATRP of St from PMTFPS‐Br, as well as the ATRP of tBA from the obtained PMTFPS‐b‐PS‐Br macroinitiators, has typical characteristic of controlled/living polymerization. The results of contact angle measurements for the films of PMTFPS‐b‐PS‐b‐PtBA triblock copolymers demonstrate that the compositions have an effect on the wetting behavior of the copolymer films. For the copolymer films with different compositions, there may be different macroscale or nanoscale structures on the outmost layer of the copolymer surfaces. The films with high content of PtBA blocks exhibit almost no ordered microstructures on the outmost layer of the copolymer surfaces, even though they have microphase‐separated structures in bulk. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Compatibilizing effect of a graft copolymer on bacterial poly(3‐hydroxybutyrate)/poly(methyl methacrylate) blends

Blends of isotactic (natural) poly(3‐hydroxybutyrate) (PHB) and poly(methyl methacrylate) (PMMA) are partially miscible, and PHB in excess of 20 wt % segregates as a partially crystalline pure phase. Copolymers containing atactic PHB chains grafted onto a PMMA backbone are used to compatibilize phase‐separated PHB/PMMA blends. Two poly(methyl methacrylate‐g‐hydroxybutyrate) [P(MMA‐g‐HB)] copolymers with different grafting densities and the same length of the grafted chain have been investigated. The copolymer with higher grafting density, containing 67 mol % hydroxybutyrate units, has a beneficial effect on the mechanical properties of PHB/PMMA blends with 30–50% PHB content, which show a remarkable increase in ductility. The main effect of copolymer addition is the inhibition of PHB crystallization. No compatibilizing effect on PHB/PMMA blends with PHB contents higher than 50% is observed with various amounts of P(MMA‐g‐HB) copolymer. In these blends, the graft copolymer is not able to prevent PHB crystallization, and the ternary PHB/PMMA/P(MMA‐g‐HB) blends remain crystalline and brittle. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1390–1399, 2002     

The Formation of Ordered Nanoholes in Binary,Chemically Similar,Symmetric Diblock Copolymer Blend Films

Summary: Binary symmetric diblock copolymer blends, that is, low‐molecular‐weight poly(styrene‐block‐methyl methacrylate) (PS‐b‐PMMA) and high‐molecular‐weight poly(styrene‐block‐methacrylate) (PS‐b‐PMA), self‐assemble on silicon substrates to form structures with highly ordered nanoholes in thin films. As a result of the chemically similar structure of the PMA and the PMMA block, the PMMA chain penetrates through the large PMA block that absorbs preferentially on the polar silicon substrate. This results in the formation of nanoholes in the PS continuous matrix.

An atomic force microscopy image of the thin film obtained from the blend of low‐molecular‐weight PS‐b‐PMMA and high‐molecular‐weight PS‐b‐PMA. The regular array of nanoholes in the films surface is clearly visible.     

Selective control over the lamellar thickness of one domain in thin binary blends of block copolymer films

Thin binary blends of poly(styrene‐b‐methyl methacrylate) (PS‐PMMA) block copolymers in films where the lamellar thickness of one domain is controlled while preserving the thickness of the other domain were demonstrated without microphase separation. One of the block copolymers used here was short and symmetric, and the other was long and asymmetric; the molecular weights of the PMMA block chains in the constituents were similar. A random copolymer brush was introduced and film thickness and composition of brush were adjusted to induce perpendicular orientation in thin film. As the blend composition of the long asymmetric block copolymer increased, the PS lamellar thickness increased from 15.8 to 25.1 nm, whereas the PMMA lamellar thickness remained constant at approximately 14 nm (the thickness decreased slightly from 14.0 to 13.3 nm). The domain spacing behavior in thin film was consistent in the bulk. These results were compared with the Birshtein, Zhulina, and Lyatskaya model and the theories for pure block copolymers in the strong segregation limit and in the intermediate segregation regime. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1393–1399