高分辨固体NMR研究不饱和聚酯/聚乙二醇-聚丙二醇-聚乙二醇三嵌段共聚物共混体系的相容性及局域分子运动

由于嵌段共聚物是制备纳米材料的可能途径之一受到广泛重视,它可以通过自组装而形成具有诸如球状、柱状及层状等复杂的形态结构[1].嵌段共聚物作为增容剂已经被大量应用在热塑性聚合物的共混改性中,但用两亲性嵌段共聚物改性热固体聚合物,如环氧树脂及不饱和聚酯等方面的工作则     

Toughness Properties of Lightly Crosslinked Epoxies Using Block Copolymers

Summary: In this work is discussed an alternative approach to the toughening of epoxy networks by the addition of acrylic block copolymers, composed of rigid and rubbery blocks. Once the reaction is completed, the initial self-assembly of block copolymers in epoxy thermoset precursors produces rubbery domains: depending on the block copolymer structure and composition, these domains are of the micrometer or the nanometer size. Nanostructures are obtained when the rigid block is a random copolymer of methylmethacrylate and N,N-dimethylacrylamide. The rubbery domains prevent rapid crack propagation and the highest toughness is obtained with filament-like microparticles or wormlike micelles.     

Nanostructured hybrid polymer networks from in situ self‐assembly of RAFT‐synthesized POSS‐based block copolymers

A series of well‐defined hybrid block copolymers PMACyPOSS‐b‐PMMA and PMAiBuPOSS‐b‐PMMA exhibiting high POSS weight contents have been synthesized by RAFT polymerization and further studied as modifiers for epoxy thermosets based on diglycidyl ether of bisphenol A. The hybrid block copolymers self‐assembled within the epoxy precursors into micelles possessing an inorganic core and a PMMA corona. Thanks to the presence of the PMMA blocks that remain miscible until the end of the reaction, curing of the resulting blends afforded nanostructured hybrid organic/inorganic networks with well‐dispersed inorganic‐rich nanodomains with diameters on the order of 20 nm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Oligo-fluoropolymer Modified Cycloaliphatic Epoxy Resins with Excellent Compatibility,Waterproof and Mechanical Properties for LED Encapsulation

An oligo-fluoropolymer(PFM) with functional cycloaliphatic epoxy and fluorinated groups was obtained via free radical polymerization and applied to the modification of cycloaliphatic epoxy resins(CE). The chemical structure of PFM was characterized by Fourier transform infrared(FTIR) spectroscopy, gel permeation chromatography(GPC) and nuclear magnetic resonance(NMR) spectroscopy, and the effects of different PFM concentrations(0.5%—6%, mass fraction) on the thermal resistance, mechanical properties, surface dewettability, light transmission, refractive index and various cured polymer properties were studied in detail. The DSC and TGA results demonstrate that the modified epoxy resins possess a higher thermal resistance than the neat epoxy resin. The improvements in the surface dewettability and water resistance are caused by the high crosslinking density and the enrichment of the oligo-fluorinated random copolymers dispersed in the matrix. The fracture surface morphologies of the thermosets were investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). It was observed that the optical transmittance of the composites was maintained even though microphase separation occurred during the curing process. With respect to the corresponding properties of the neat epoxy resins, the 2 phr(parts per hundreds of resin) PFM thermoset exhibited relatively better comprehensive properties, making the cured material a good candidate for light-emitting diode(LED) encapsulation.     

Synthesis and Microphase Separation Behavior of Random,Mixed Cylindrical Brush Copolymers Bearing Polystyrene and Poly(ε-caprolactone) Side Chains

A series of mixed, random cylindrical brush copolymers bearing polystyrene(PS) and poly(ε-caprolactone)(PCL) side chains were synthesized via the combination of ring-opening polymerization(ROP) and atom transfer radical polymerization(ATRP). These novel cylindrical brush copolymers have been characterized by means of nuclear magnetic resonance(NMR) spectroscopy, gel permeation chromatography(GPC) and differential scanning calorimetry(DSC). It was found that the mikto-armed cylindrical brush copolymers were microphase-separated in bulks and that the morphologies were dependent on the mass ratios of PS to PCL side chains. One of the cylindrical brush copolymers was employed to incorporate into epoxy thermoset to investigate effect of the mikto-armed cylindrical brush architecture on the reaction-induced microphase separation behavior. Depending on the concentration of the cylindrical brush in epoxy, the thermosets can display the morphologies with the spherical, worm-like and lamellar PS microdomains dispersing in continuous thermosetting matrices.     

Synthesis and microphase separation behavior of random,mixed cylindrical brush copolymers bearing polystyrene and poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) side chains

A series of mixed, random cylindrical brush copolymers bearing polystyrene (PS) and poly(ε-caprolactone) (PCL) side chains were synthesized via the combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). These novel cylindrical brush copolymers have been characterized by means of nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). It was found that the mikto-armed cylindrical brush copolymers were microphase-separated in bulks and that the morphologies were dependent on the mass ratios of PS to PCL side chains. One of the cylindrical brush copolymers was employed to incorporate into epoxy thermoset to investigate effect of the mikto-armed cylindrical brush architecture on the reaction-induced microphase separation behavior. Depending on the concentration of the cylindrical brush in epoxy, the thermosets can display the morphologies with the spherical, worm-like and lamellar PS microdomains dispersing in continuous thermosetting matrices.     

液体氯丁二烯-甲基丙烯酸羟乙酯共聚物改性环氧树脂——N,N-二甲基苄胺固化体系

本工作制备了一系列以N,N-二甲基苄胺为固化剂的液体氯丁二烯-甲基丙烯酸羟乙酯共聚物改性环氧树脂固化物。研究了液体共聚物用量和固化条件对改性体系物理性能的影响。用红外光谱法和固化仪方法,测定了固化反应速度,讨论了固化反应机理。用扫描电镜的方法,观察了液体共聚物用量和固化条件对改性体系形态结构的影响。     

Short-block polyurea-polydimethylsiloxane block copolymers based on secondary diamines

New short-block polyurea-polydimethylsiloxane block copolymers based on aliphatic and alicyclic secondary diamines and diisocyanates as well as on oligodimethylsiloxanes with glycidyl end groups were synthesized through a two-stage method. With the use of DSC and small-angle X-ray scattering methods, it was shown that, in the resulting block copolymers, in spite of the short block lengths, microphase separation occurs. The sizes of the formed domains, which correspond to the interplanar distances, decrease monotonically with a decrease in the sizes of the rigid and elastic blocks and become as low as 6.0–11.1 nm. The stress-strain characteristics of block copolymers are dependent above all on the ratio of blocks.     

Phase behavior,crystallization, and nanostructures in thermoset blends of epoxy resin and amphiphilic star‐shaped block copolymers

This article reports thermoset blends of bisphenol A‐type epoxy resin (ER) and two amphiphilic four‐arm star‐shaped diblock copolymers based on hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(propylene oxide) (PPO). 4,4′‐Methylenedianiline (MDA) was used as a curing agent. The first star‐shaped diblock copolymer with 70 wt % ethylene oxide (EO), denoted as (PPO‐PEO)₄, consists of four PPO‐PEO diblock arms with PPO blocks attached on an ethylenediamine core; the second one with 40 wt % EO, denoted as (PEO‐PPO)₄, contains four PEO‐PPO diblock arms with PEO blocks attached on an ethylenediamine core. The phase behavior, crystallization, and nanoscale structures were investigated by differential scanning calorimetry, transmission electron microscopy, and small‐angle X‐ray scattering. It was found that the MDA‐cured ER/(PPO‐PEO)₄ blends are not macroscopically phase‐separated over the entire blend composition range. There exist, however, two microphases in the ER/(PPO‐PEO)₄ blends. The PPO blocks form a separated microphase, whereas the ER and the PEO blocks, which are miscible, form another microphase. The ER/(PPO‐PEO)₄ blends show composition‐dependent nanostructures on the order of 10?30 nm. The 80/20 ER/(PPO‐PEO)₄ blend displays spherical PPO micelles uniformly dispersed in a continuous ER‐rich matrix. The 60/40 ER/(PPO‐PEO)₄ blend displays a combined morphology of worm‐like micelles and spherical micelles with characteristic of a bicontinuous microphase structure. Macroscopic phase separation took place in the MDA‐cured ER/(PEO‐PPO)₄ blends. The MDA‐cured ER/(PEO‐PPO)₄ blends with (PEO‐PPO)₄ content up to 50 wt % exhibit phase‐separated structures on the order of 0.5–1 μm. This can be considered to be due to the different EO content and block sequence of the (PEO‐PPO)₄ copolymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 975–985, 2006     

Polymerization Induced Microphase Separation for the Fabrication of Nanostructured Materials

Polymerization induced microphase separation (PIMS) is a strategy used to develop unique nanostructures with highly useful morphologies through the microphase separation of emergent block copolymers during polymerization. In this process, nanostructures are formed with at least two chemically independent domains, where at least one domain is composed of a robust crosslinked polymer. Crucially, this synthetically simple method is readily used to develop nanostructured materials with the highly coveted co-continuous morphology, which can also be converted into mesoporous materials by selective etching of one domain. As PIMS exploits a block copolymer microphase separation mechanism, the size of each domain can be tightly controlled by modifying the size of block copolymer precursors, thus providing unparalleled control over nanostructure and resultant mesopore sizes. Since its inception 11 years ago, PIMS has been used to develop a vast inventory of advanced materials for an extensive range of applications including biomedical devices, ion exchange membranes, lithium-ion batteries, catalysis, 3D printing, and fluorescence-based sensors, among many others. In this review, we provide a comprehensive overview of the PIMS process, summarize latest developments in PIMS chemistry, and discuss its utility in a wide variety of relevant applications.     

A furan-derived epoxy thermoset with inherent anti-flammability,degradability, and raw material recycling

The production of multifunctional thermosets with flammability, degradability and raw material recycling from epoxy thermosets made from renewable resources is one of the hottest topics in the context of sustainable development. In this work, we fabricated a fully bio-based epoxy thermoset by curing an as-synthesized furan-derived epoxy monomer (HMF-DDDS-EP) with a furan-based hardener (DFA). Owing to its unique structure containing a Schiff base and disulfide bonds, the cured HMF-DDDS-EP/DFA thermoset integrates a high glass transition temperature, high tensile strength, inherent anti-flammability, degradability, and recyclability. Specifically, a glass transition temperature as high as 171 °C, tensile strength of 62.9 MPa, a storage modulus of 2,356 MPa and outstanding anti-flammability (UL-94 V-0 rating and high LOI of 36.0%) were observed for this fully bio-based epoxy thermoset. Additionally, it was capable of degrading under mildly acidic conditions because of the cleavage of the Schiff base into the original aldehyde monomer. This fully bio-based epoxy thermoset can be considered a representative for fostering the synthesis of advanced thermosetting materials derived from renewable resources.     

Competition Between Interfacial Interaction and Microphase Separation in Crystallization of Filled Block Copolymers

Understanding the effect of repulsive interaction between blocks on crystallization in block copolymers is beneficial for the design and development of sophisticated nanostructures. Dynamic Monte Carlo simulations were performed to reveal the crystallization mechanism of block copolymers containing one‐dimensional nanofiller under different repulsive interaction strengths between crystallizable and noncrystallizable blocks. During crystallization, crystalline morphology is determined by the competition between segmental orientation perpendicular to microphase interfaces dominated by microphase separation and that along the direction of the long axis of the nanofiller controlled by interfacial interaction. As the repulsive interaction between different blocks is strengthened, the competition between microphase separation and interfacial interaction is intensified, eventually leading to an increase in crystallization rate and a degradation in crystalline morphology. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1516–1526     

Synthesis and investigation of polyphenyldimethylsiloxane block copolymers with bimodal chain length distribution of oligodimethylsiloxane blocks

Siloxane block copolymers containing linear dimethylsiloxane (DMS) and cyclolinear phenylsilsesquioxane blocks were synthesized. A peculiarity of the copolymers is a bimodal distribution of linear DMS blocks in the polymer chain. The results of X-ray diffraction. thermomechanical, and DSC studies of bimodal block copolymers indicate a higher degree of microphase separation of the blocks as compared to unimodal block copolymers. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1542–1546, September, 2000.     

Main-chain supramolecular block copolymers

Block copolymers are key building blocks for a variety of applications ranging from electronic devices to drug delivery. The material properties of block copolymers can be tuned and potentially improved by introducing noncovalent interactions in place of covalent linkages between polymeric blocks resulting in the formation of supramolecular block copolymers. Such materials combine the microphase separation behavior inherent to block copolymers with the responsiveness of supramolecular materials thereby affording dynamic and reversible materials. This tutorial review covers recent advances in main-chain supramolecular block copolymers and describes the design principles, synthetic approaches, advantages, and potential applications.     

Picket‐Fence Polythiophene and its Diblock Copolymers that Afford Microphase Separations Comprising a Stacked and an Isolated Polythiophene Ensemble

All‐polythiophene diblock copolymers, comprising one unsheathed block and one fenced block, were synthesized through catalyst‐transfer polycondensation. The unsheathed block self‐assembles through π‐π stacking, thereby inducing microphase separation. Consequently, we have succeeded in creating a microphase separation comprising an ensemble of stacked and isolated polythiophenes. This achievement could be extended to various unexplored applications as a result of the integration of the contrasting functions of the two blocks.     

Control of the block copolymer morphology in templated epoxy thermosets

It has been found that by the addition of low concentrations of an amphiphilic block copolymer to an epoxy resin, novel disordered morphologies can be formed and preserved through curing. This article will focus on characterizing the influence of the block copolymer and casting solvent on the templated morphology achieved in the thermoset sample. The ultimate goal of this work is to determine the parameters that would control the microphase morphology produced. Epoxy resins blended with a series of amphiphilic block copolymers based on hydrogenated polyisoprene (polyethylene-alt-propylene or PEP) and polyethylene oxide (PEO), specifically, were investigated. In this article, the cure-induced order–order phase transition from the spherical to wormlike micelle morphology will also be discussed. It is proposed that the formation of the wormlike micelle structure from the spherical micelle structure is similar to the phase transition behavior that occurs in dilute block copolymer solutions as a function of the influence of the solvent on micelle morphology. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3338–3348, 2007     

Flame retardant and toughening behaviors of bio‐based DOPO‐containing curing agent in epoxy thermoset

Based on bio‐based furfural, a phosphorus‐containing curing agent (FPD) was successfully synthesized, via the addition reaction between 9,10‐dihydro‐9‐oxa‐10 phosphaphenanthrene‐10‐oxide (DOPO) and furfural‐derived Schiff base. Then, as co‐curing agent, FPD was used to prepare flame retardant epoxy thermosets (EP) cured by 4, 4′‐diaminodiphenyl methane. The incorporated FPD improved the flame retardancy and toughness of epoxy thermoset, simultaneously. When 5 wt% FPD was added into EP, the FPD/EP achieved 35.7% limited oxygen index (LOI) value and passed UL94 V‐0 rating, meanwhile. In FPD/EP thermoset, the incorporated FPD reduced the thermal decomposition rate, increased the charring capacity, and inhibited the combustion intensity of epoxy thermoset. Through gas‐phase and condensed‐phase actions in weakening fuel supply, suppressing volatile combustion, and enhancing charring barrier effect, FPD decreased the heat release of burning epoxy thermoset, significantly. For the outstanding effectiveness on both flame retardancy and toughness, the study on FPD provides a promising way to manufacture high‐performance epoxy thermoset.     

Nanostructured epoxy thermoset templated by an amphiphilic PCL‐b‐PES‐b‐PCL triblock copolymer

The PCL‐b‐PES‐b‐PCL triblock copolymer is used to incorporate into epoxy resin when the blends are cured with 4,4'‐diaminodiphenylsulfone (DDS) to afford the nanostructured epoxy thermosets. The differential scanning calorimetry (DSC) and Fourier transform‐infrared spectroscopy (FT‐IR) show that the nanostructured PCL‐b‐PES‐b‐PCL thermosets are accessed through the formation of the intermolecular hydrogen bonding interactions. The nanostructures are further evidenced by means of small‐angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM). By considering the miscibility of the subchains of block copolymer with epoxy before and after the curing reaction, it is judged that the formation of the nanostructures follows the mechanism of reaction‐induced microphase separation. It is noted that the epoxy resin is significantly toughened in terms of the measurement of critical stress field intensity factor (K_IC). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 424–432     

Effects of annealing on crystallinity and phase behaviour of PET/PC block copolymers

The effects of the annealing on the properties of PET/PC block copolymers, obtained by reactive blending in the presence of different catalysts and for different mixing times, have been studied. The annealing, performed in conditions that promote the crystallization, has been used to better understand the role of block length in determining the phase behaviour. The copolymers characterized by blocks with molecular weight larger than 8000 are able to reorganize towards more ordered domains. This rearrangement maintains the phase separation, as two crystalline phases are present before and after annealing, due to the immiscibility of long blocks. In copolymers characterized by blocks with molecular weight equal to about 2500, that is the higher limit for the miscibility in the amorphous state in PET/PC block copolymers studied in this work, the rearrangement of the chains during annealing causes a phase separation leading to two crystalline phases. Only in the copolymers with molecular weight of blocks lower than 1500, the very short block length hinders the crystallization: therefore, only in this case a phase separation does not take place after annealing.     

New flame retardant epoxy resins based on cyclophosphazene-derived curing agents

To obtain high-efficiency flame retardancy of epoxy resins, a cyclophosphazene derivative tri-(o-henylenediamino)cyclotriphosphazene (3ACP) was successfully synthesized and used as a curing agent for the thermosetting of an epoxy resin system. The flame retardant properties, thermal stability, and pyrolysis mechanism of the resultant thermosets were investigated in detail. The experiments indicated that the synthesized thermoset achieved a UL-94 V-0 rate under a vertical burning test as well as a limiting oxygen index (LOI) of 29.2%, which was able to reach V-0 even when a small amount of 3ACP was incorporated. Scanning electronic microscopic observation demonstrated that the char residue of the thermosets was extremely expanded after the vertical flame test. Thermal analysis showed that the samples had a lower initial decomposition temperature when 3ACP was introduced into the epoxy resin systems. This indicates that the carbonization ability of the thermosets was significantly improved at elevated temperatures. In addition, the incorporation of 3ACP can effectively suppress the release of combustible gases during the pyrolysis process, and the decomposition of E-44/DDS-3ACP curing systems also promotes the formation of polyphosphoramides charred layer in the condensed phase. The investigation on the chemical structures of both the gaseous and condensed phase pyrolysis process confirmed the flame-retardant mechanism of the 3ACP-cured epoxy resins. Therefore, the nonflammable halogen-free epoxy resin developed in this study has potential applications in electric and electronic fields for environment protection and human health.