Synthesis and investigation of properties of silaoxadihydrophenanthrene‐diphenylsiloxane fragments containing block copolymers

The reaction of heterofunctional condensation of 1,1‐dichloro‐1‐sila‐2‐oxadihydrophenanthrene with dihydroxydiphenylsilane at various ratios of initial compounds in the presence of pyridine is investigated. α,ω‐Dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxane oligomers with various degrees of condensation are obtained. Organosiloxane block copolymers with the regular arrangement of silaoxadihydrophenanthrene‐diphenylsiloxanes fragments in the main linear dimethylsiloxane chain are produced by the reaction of heterofunctional condensation of α,ω‐dihydroxysilaoxadihydrophenanthrene‐diphenylsiloxanes with α,ω‐dichlorodimethylsiloxanes in the presence of anhydrous pyridine, as an acceptor of hydrochloric acid. Thermogravimetry, differential scanning calorimetry, gel permeation chromatography, and wide‐angle X‐ray analysis are carried out on the synthesized block copolymers. The microheterogeneous structure of block copolymers is observed at definite values of the length of the flexible dimethylsiloxane chain by DSC and X‐ray investigation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 9–16, 2002; DOI 10.1002/app.10045     

Segmented Block Copolymers with Monodisperse Hard Segments: The Influence of H‐Bonding on Various Properties

The properties of segmented‐copolymer‐based H‐bonding and non‐H‐bonding crystallisable segments and poly(tetramethylene oxide) segments were studied. The crystallisable segments were monodisperse in length and the non‐hydrogen‐bonding segments were made of tetraamidepiperazineterephthalamide (TPTPT). The polymers were characterised by DSC, FT‐IR, SAXS and DMTA. The mechanical properties were studied by tensile, compression set and tensile set measurements. The TPTPT segmented copolymers displayed low glass transition temperatures (T_g, ?70 °C), good low‐temperature properties, moderate moduli (G′ ≈ 10–33 MPa) and high melting temperatures (185–220 °C). However, as compared to H‐bonded segments, both the modulus and the yield stress were relatively low.

     

Nanostructuration of Unsaturated Polyester by All‐Acrylic Block Copolymers, 1 ‐ Use of High‐Molecular‐Weight Block Copolymers

Nanostructuration of maleate and orthophthalic unsaturated polyester (UP) resins was achieved by the use of high molecular weight amphiphilic PBA‐b‐P(MMA‐co‐DMA)₂ triblock copolymers. PBA is fully immiscible in cured UP resins, and the miscibility of P(MMA‐co‐DMA) random copolymers can be ensured with a minimum DMA content of 12 mol‐%. When using the triblock copolymers, fully transparent and nanostructured thermosets are obtained with a minimum DMA content in the outer blocks; the value of which is higher than 12 mol‐% and depends on the UP chemical structure. Finally, the fracture toughness of nanostructured thermoset was evaluated: for a triblock copolymer content as low as 5 wt.‐%, a 50% increase of K_Ic was obtained, as compared to the neat thermoset.

     

两亲扩展型共聚物的合成及中间极性嵌段对乳化性能的影响

采用聚乙二醇单甲醚(Mn=1 900,5 000)分别引发丙交酯和ε-己内酯开环聚合合成了中间嵌段(PLA)聚合度递增的聚乙二醇-聚丙交酯-聚己内酯(MPEG-PLA-PCL)两亲扩展型共聚物和相应的聚乙二醇-聚己内酯(MPEG-PCL)两嵌段共聚物。用FTIR、1HNMR和GPC对产物结构进行了表征,研究了共聚物和常规低分子表面活性剂的乳化性能,探讨了中间极性嵌段的长度对共聚物乳化性能的影响。结果表明,对于甲苯/水体系,共聚物可用于制备稳定的O/W型乳液,且三嵌段共聚物的乳化性能优于低分子表面活性剂;随着引入PLA嵌段聚合度的增加,共聚物的乳化能力呈先增加后减小的趋势;相对于MPEG1900系列共聚物,MPEG5000系列共聚物中需要引入更长的中间嵌段才能获得最佳乳化性能。     

Glycidyl Azide‐butadiene Block Copolymers: 2 Synthesis from a Mesylated Precursor

Glycidyl azide‐butadiene block copolymers are potential binders for solid propellants. The azidic part contributes to the overall energy outputs, while the butadiene block improves the mechanical properties. Synthetic strategies proposed in literature are not appropriate for production of large‐scale quantities. The mesylation of one homopolymer, followed by reaction with the OH terminal groups of the second is proposed here. The reaction is simple and does not show the drawbacks of the previously suggested alternatives. The block copolymers can be used as “partially” energetic binders. Moreover, they work well as compatibilizer in mechanical blends of the two homopolymers, that otherwise rapidly segregate in two distinct phases.     

Synthesis and Thermal Characterization of Some Novel ABA Block Copolymers

The synthesis of some novel ABA block copolymers is reported. The block A is a PPO while the block B is a random copoly(aryl ether sulfone), synthesized with three different molecular weights. The block copolymers were obtained by a two step procedure consisting on the functionalization of the random copoly(aryl ether sulfone) followed by a condensation with PPO. Spectroscopic techniques (¹H NMR and ¹³C NMR) were used to characterize the polymers obtained from each step. The NMR data proved the complete conversion of amino groups after the first reaction step and gave some useful insights on the completion of the second step. Copolymer formation is supported by a comparison of the thermal behavior of the block copolymers with respect to the physical blends of the two homopolymers. DSC and DMA analyses showed double glass transitions for the physical blends which could be related to the immiscibility of the two homopolymers, while, in contrast, the block copolymer showed single glass transition. Blends of ABA triblock copolymer/PPO and of ABA triblock/copoly(arylen ether sulfone)s were also prepared. These blends, tested by DSC, showed a good level of compatibility of the ABA copolymer with its singular constituents.

     

Micromechanisms of Tack of Soft Adhesives Based on Styrenic Block Copolymers

The tackiness of model soft adhesive layers based on styrene‐isoprene‐styrene block copolymers and a tackifying resin were investigated with a flat‐ended cylindrical steel probe. The contact between the probe and the adhesive was maintained for 1 s at a nominal pressure of 1 MPa before being detached at a constant velocity. The effect of resin content, probe velocity during debonding and temperature were systematically investigated. Failure was initiated by two main mechanisms: an interfacial cavitation at low debonding rates, giving relatively low adhesion energies, and a bulk cavitation process at higher debonding rates, which gave much higher adhesion energies. In both cases failure occurred at the end by interfacial detachment of fibrils. The characteristic probe velocity where the transition between these two mechanisms took place was controlled primarily by the linear viscoelastic properties of the adhesives. However, the important quantitative parameters obtained from a tack test, i.e., the maximum debonding stress and the adhesion energy, could not be predicted by the linear viscoelastic properties of these adhesives alone.     

Chain‐linked lactic acid polymers by benzene diisocyanate

Chain‐linked lactic acid polymers with high molecular weight were synthesized by two‐step polymerization method, including polycondensation and chain extending reactions. The effects of chain extender toluene diisocyanate (TDI) on the chain‐linked lactic acid polymers were studied. The polymers obtained were characterized by gel permeation chromatography, fourier transform infrared spectroscopy, ¹H NMR, and differential scanning calorimeter. Reactions between 1,4‐butanediol and lactic acid oligomers led to hydroxyl‐terminated prepolymer, which provided significant increase of molecular weight in the chain extending reaction. In addition, the glass transition temperature (T_g) and the melting temperature (T_m) were increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1045–1049, 2006     

Synthesis and Characterization of Segmented Block Copolymers Based on Hydroxyl‐Terminated Liquid Natural Rubber and α,ω‐Diisocyanato Telechelics

Summary: Segmented block copolymers, consisting of non‐polar soft segments from hydroxyl‐terminated liquid natural rubber (HTNR) and polar hard segments from α,ω‐diisocyanato telechelics obtained by “criss‐cross”‐cycloaddition, have been synthesized. The block copolymer formation took place under relatively mild reaction conditions at 80 °C in dichloroethane in the presence of dibutyltin dilaurate as a catalyst. The resulting block copolymers were characterized by spectroscopic techniques (¹H NMR, FTIR, UV‐vis spectroscopy) as well as GPC for molar mass determination. The block copolymers were compression molded in a hot stage press, and the resulting samples were characterized by DSC and stress‐strain measurement. The solubility and phase morphology of the materials have also been studied.

Segmented block copolymer from HTNR and α,ω‐diisocyanato telechelics     

Assessment of random aromatic co‐polyamides containing two different bulky pendant groups

This work reports the synthesis and assessment of random aromatic co‐polyamides containing two different bulky pendant groups. The random aromatic co‐polyamides are synthesized combining the monomers 5‐tert‐butylisophthalic acid and 5‐(9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dicarboximido)isophthalic acid with three different diamines. The random aromatic co‐polyamides are readily soluble and possess inherent viscosities in the range of 0.47–0.60 dL g⁻¹. Co‐polyamide dense membranes are amorphous, and flexible with both good tensile strength (56.2–57.5 MPa) and tensile modulus (1.3–1.6 GPa). Permeability coefficients of the co‐polyamide dense membranes are assessed for the gases He, O₂, N₂, CH₄, and CO₂. It is found that the combination of two bulky pendant groups, dibenzobarrelene and tert‐butyl, in the backbone of the co‐polyamides improves the gas permeability coefficient in comparison with their corresponding homopolyamides. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45884.     

Synthesis of polydimethylsiloxane‐containing block copolymers via reversible addition fragmentation chain transfer (RAFT) polymerization

Low polydispersity polydimethylsiloxane (PDMS) was end functionalized with a reversible addition fragmentation chain transfer (RAFT) agent by the esterification of hydroxyl terminated PDMS with a carboxylic acid functional RAFT agent. These PDMS‐RAFT agents were able to control the free radical polymerization of styrene and substituted styrene monomers to produce PDMS‐containing block copolymers with low polydispersities and targeted molecular weights. A thin film of polydimethylsiloxane‐block‐polystyrene was prepared by spin coating and exhibited a microphase separated morphology from scanning force microscopy measurements. Controlled swelling of these films in solvent vapor produced morphologies with significant long‐range order. This synthetic route will allow the straightforward production of PDMS‐containing block copolymer libraries that will be useful for investigating their thin film morphological behavior, which has applications in the templating of nanostructured materials.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Self‐Assembling of SBS Block Copolymers as Templates for Conductive Silver Nanocomposites

Novel nanocomposites based on conductive Ag nanoparticles and a self‐assembled polystyrene‐block‐polybutadiene‐block‐polystyrene (SBS) block copolymer were investigated. Good confinement of the nanoparticles into polystyrene microphase was achieved by the addition of DT as surfactant. The polymeric matrix kept its hexagonal order packed cylindrical structure up to 7 wt.‐% content of Ag nanoparticles. An electrostatic force microscopy (EFM) analysis of well‐dispersed metal‐organic hybrid Ag/SBS films was used to characterize the electric behavior of the conductive nanocomposites.

     

Structural and ordering behavior of lamellar polystyrene‐block‐polybutadiene‐block‐polystyrene triblock copolymer containing layered silicates

Nanocomposites based on organically modified montmorillonites (OMMTs) and sodium montmorillonite (CLO‐Na⁺) with poly(styrene‐b‐butadiene‐b‐styrene) (SBS) diblock copolymer have been investigated. Solution blending of OMMT suspension in toluene with SBS and subsequent static casting and annealing resulted in transparent films. Final samples were processed by compression molding. The intercalation spacing in the nanocomposites, microphase separation of the SBS, and the degree of dispersion of nanocomposites were investigated by X‐ray diffraction (Wide and small‐angle X‐ray scattering), transmission optical microscopy (TOM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The increase of basal spacing of OMMT in the nanocomposites suggested the intercalation of SBS. The lamellar structure perfection was extensively affected by both OMMT. AFM images and TOM micrographs only showed well dispersed but not exfoliated nanocomposites. On the other hand, TEM showed inserted tactoids into both blocks depending on the surfactant used (stained samples) and the dispersion of those tactoids (unstained samples). Fourier transform infrared spectroscopy indicated only the presence of the OMMT into the SBS. Deviations of the decomposition pathway of pristine SBS with addition of the OMMT were found by thermogravimetric analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

苯乙烯类嵌段共聚物的国内外市场

分析了国内外苯乙烯类嵌段共聚物(SBC)的供需状况，提出了发展我国SBC生产的一些建议。     

Molecular‐Weight‐Controlled Brittle‐to‐Semiductile‐to‐Ductile Transition in S‐(S/B)‐S Triblock Copolymers

Toughness enhancement of S‐(S/B)‐S triblock copolymers via a molecular‐weight‐controlled pathway is demonstrated. The post‐yield crack toughness behavior of the triblock copolymers uniquely reveal a brittle‐to‐semiductile‐to‐ductile transition with increasing while keeping the basic molecular architecture fixed. TEM and SAXS investigations indicated three distinct morphologies as a function of χ_effN as a consequence of the increase in : (i) a homogeneous structure without phase‐separation, (ii) a weakly segregated structure, and (iii) a lamellar structure. The increase in crack toughness is also reaffirmed from kinetic and strain field analysis studies concerning dynamics of crack growth in block copolymers with high PS content.

     

Controlled and stereospecific polymerization of rac‐lactide with a single‐site ethyl aluminum and alcohol initiating system

A single‐site ethyl aluminum complex, [2,2‐ diethyl‐1,3‐propylenebis(3,5‐di‐tert‐butyl‐salicylideneiminato)] ethyl aluminum (2), with a geminal diethyl substitutent on the diamino bridge was synthesized by the reaction of AlEt₃ with 1 equiv of N,N′‐(2,2‐diethyl‐1,3‐propylene)bis(3,5‐di‐tert‐butylsalicylideneimine). X‐ray diffraction showed that complex 2 contained a five‐coordinate aluminum atom with a distorted trigonal bipyramidal geometry in the solid state. ¹H‐NMR and ¹³C‐NMR spectra indicated that the two conformational enantiomers of 2 tautomerized quickly on the NMR timescale in solution. In the presence of isopropyl alcohol, the ring‐opening polymerization (ROP) of rac‐lactide with complex 2 produced a crystalline stereoblock polylactide (PLA). The stereoblocks contained an average of 12 units (L? = 12) of enantiomerically pure lactic acid. There was a linear relationship between the monomer conversion and number‐average molecular weights of the polymer. An induction period was observed for the polymerization. The induction period increased with decreasing concentration of catalyst 2 and isopropyl alcohol. In the presence of poly(ethylene glycol) (PEG), a PLA/PEG/PLA stereocomplex was prepared directly by the ROP of rac‐lactide with complex 2, which was confirmed by NMR, gel permeation chromatography, wide‐angle X‐ray diffraction, and differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 102–108, 2005     

Continuous Flow Fabrication of Block Copolymer–Grafted Silica Micro‐Particles in Environmentally Friendly Water/Ethanol Media

Polymer‐grafted inorganic particles (PGIPs) are attractive building blocks for numerous chemical and material applications. Surface‐initiated controlled radical polymerization (SI‐CRP) is the most feasible method to fabricate PGIPs. However, a conventional in‐batch reaction still suffers from several disadvantages, including time‐consuming purification processes, low grafting efficiency, and possible gelation problems. Herein, a facile method is demonstrated to synthesize block copolymer–grafted inorganic particles, that is, poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA)‐b‐poly(N‐isopropylacrylamide) (PNIPAM)–grafted silica micro‐particles using continuous flow chemistry in an environmentally friendly aqueous media. Immobilizing the chain transfer agent and subsequent SI‐CRP can be accomplished sequentially in a continuous flow system, avoiding multi‐step purification processes in between. The chain length (MW) of the grafted polymers is tunable by adjusting the flow time or monomer concentration, and the narrower molar mass dispersity (Р< 1.4) of the grafted polymers reveals the uniform polymer chains on the particles. Moreover, compared with the in‐batch reaction at the same condition, the continuous system also suppresses possible gelation problems.     

Synthesis and Characterization of Polystyrene-b-Poly(4-vinyl pyridine) Block Copolymers by Atom Transfer Radical Polymerization

We aimed at the synthesis of well-define PS-b-P4VP by using atom transfer radical polymerization in two-step process. First, polystyrenes with benzyl bromide end group (PS-Br; by ATRP) were prepared as macroinitiator for the next ATRP of 4-vinyl pyridine and characterized these polymers from ¹H-NMR and MALDI-TOF. Comparing with MALDI-TOF-MS, ¹H-NMR and GPC analyses, this indicates that the formation of the block copolymer can be observed. During the polymerizations, molecular weight distribution and kinetics have been evaluated from GPC traces and ¹H-NMR analyses. We further characterized the thermal properties of these block polymers by DSC and TGA. DSC measurement on the PS-b-P4VP block copolymers exhibited two glass transitions, indicating that the resulting block copolymers are phase separated. Two maxima differential peaks were observed on the TGA trace for the PS-b-P4VP block copolymers might be assigned to the decomposition of the P4VP blocks at 380 ^○C and the PS blocks at higher temperature.