Polystyrene (PST) macromonomers having several allyl groups at the ends were synthesized by the mechanical scission reaction of the main chain in the presence of diallylmalonic acid diethyl ester (DAME). Photosensitive benzophenone groups were introduced on a PST macromonomer molecule by the reaction of these PST macromonomers with benzoyl chloride. The palm-treelike (PST–poly-4-vinylpyridine (P4VP)) sequential copolymers with different compositions were prepared by the radical copolymerization of PST macromonomer with 4VP. The morphological observation of these sequential copolymers was carried out by the transmission electron microscopy. The PST block microdomains were fixed by photocrosslinks (UV irradiation) in the presence of mono- and bifunctional unsaturated compounds in the state of mesomorphic structures. The microdomain fixing of P4VP blocks was carried out by using the vapor of 1, 4-dibromobutane (DBB). After subsequent chemical modifications (quaternization of residual P4VP blocks and sulfonation of PST blocks), the effect of microdomain fixings was elucidated from the moisture content of positive and negative regions. These results are discussed in some detail. 相似文献
Well defined BAB-type poly[styrene(ST)-b-2-methyl-2-oxazoline(MeOz)] was prepared by the cationic polymerization of α,ω-p-toluenesulfonic acid ester-terminated PST (PST-BTs) as an initiator. Alkaline hydrolysis of this block copolymer was carried out under various reaction conditions to obtain BAB-type poly[ST-b-ethylene imine(EI)]. Morphologies of these block copolymer specimens cast from several solvents were observed by electron microscope. The results are discussed in some detail. 相似文献
The syntheses of poly(m-phenylene isophthalamide-b-ethylene oxide) and poly(m-phenylene isophthalamide-b-dimethylsiloxane) are reported. The development of synthesis procedures for (AB)n and predominantly triblock ABA and BAB sequences are discussed. Chemical compositions, dilute solution viscosities, and solubility behavior of these systems are also given some consideration. These considerations include the problems that arise in condensing block segments together when phase separation is occurring and developing control of the synthesis procedure to produce block systems of varying compositions. 相似文献
This paper describes a new approach towards preparing self‐assembled hydrogen‐bonded complexes that have vesicle and patched spherical structures from two species of block copolymer in non‐selective solvents. The assembly of vesicles from the intermolecular complex formed after mixing polystyrene‐block‐poly(4‐vinyl phenol) (PS‐b‐PVPh) with poly(methyl methacrylate)‐block‐poly(4‐vinylpyridine) (PMMA‐b‐P4VP) in tetrahydrofuran (THF) is driven by strong hydrogen bonding between the complementary binding sites on the PVPh and P4VP blocks. In contrast, well‐defined patched spherical micelles form after blending PS‐b‐PVPh with PMMA‐b‐P4VP in N,N‐dimethylformamide (DMF): weaker hydrogen bonds form between the PVPh and P4VP blocks in DMF, relative to those in THF, which results in the formation of spherical micelles that have compartmentalized coronas that consist of PS and PMMA blocks.
We report a new approach toward preparing self-assembled hydrogen-bonded complexes having vesicle and patched spherical structures from two species of block copolymers in nonselective solvents. Two diblock copolymers, poly(styrene-b-vinyl phenol) (PS-b-PVPh) and poly(methyl methacrylate-b-4-vinylpyridine) (PMMA-b-P4VP), were synthesized through anionic polymerization. The assembly of vesicles from the intermolecular complex formed after mixing PS-b-PVPH with PMMA-b-P4VP in THF was driven by strong hydrogen bonding between the complementary binding sites on the PVPH and P4VP blocks. In contrast, well-defined patched spherical micelles formed after blending PS-b-PVPh with PMMA-b-P4VP in DMF: the weaker hydrogen bonds formed between the PVPh and P4VP blocks in DMF, relative to those in THF, resulted in the formation of spherical micelles having compartmentalized coronas consisting of PS and PMMA blocks. 相似文献
Worm‐like aggregates with a PAA/P4VP complex core and a PEG/PNIPAM mixed shell were prepared in ethanol by the comicellization of poly(ethylene glycol)‐block‐poly(acrylic acid) (PEG‐b‐PAA) and poly(N‐isopropylacrylamide)‐block‐poly(4‐vinylpyridine) (PNIPAM‐b‐P4VP) through hydrogen‐bonding. The formed aggregates were studied by dynamic light scattering, static light scattering, 1H NMR, and transmission electron microscopy. The length of worm‐like aggregates could be adjusted by changing the weight ratio of W(PNIPAM‐b‐P4VP)/W(PEG‐b‐PAA). When the ratio changed from 20 to 150%, the length changed from about 100 nm to several microns, and the diameter stayed almost unchanged at about 15 nm.
Silver nanoparticles (Ag NPs) of improved thermal stability against long‐term aggregation were prepared using the polystyrene‐b‐poly(4‐vinylpyridine)‐b‐polystyrene (PS‐b‐P4VP‐b‐PS) triblock copolymer as a multidentate ligand. First, PS‐b‐P4VP‐b‐PS was synthesized by sequential reversible addition–fragmentation transfer (RAFT) polymerization of styrene and 4‐vinylpydine using a trithiocarbonate chain transfer agent (CTA). Then Ag NPs were obtained by in situ reduction of silver nitrate using PS‐b‐P4VP‐b‐PS as a multidentate ligand. The obtained Ag NPs were stable in solution for at least 24 h while being heated at 110°C. The effect of the molar ratio of N atoms of the P4VP chain segment and AgNO3 on the stability of Ag NPs was studied, and the results suggested that Ag NPs were very stable even if the molar ratio of N atoms of the P4VP chain segment and AgNO3 was very low. This method is promising to scale up the preparation of metal NPs with good dispersibility and thermal stability, which still remains challenging. To further improve its thermal stability, 1,4‐dibromobutane was used to chemically crosslink the P4VP chain segment in solution. However, the results proved that the crosslink method is infeasible to further improve the thermal stability of Ag NPs in this system. 相似文献
Linear poly(4‐tert‐butoxystyrene)‐b‐poly(4‐vinylpyridine) (PtBOS‐b‐P4VP) diblock copolymers are synthesized using reversible addition–fragmentation chain transfer polymerization. The self‐assembly of four different PtBOS‐b‐P4VP diblock copolymers is studied using small‐angle X‐ray scattering and transmission electron microscopy and a number of interesting observations are made. A tBOS62‐b‐4VP28 diblock copolymer with a weight fraction P4VP of 0.21 shows a disordered morphology of P4VP spheres with liquid‐like short‐range order despite an estimated value of of the order of 50. Increasing the length of the 4VP block to tBOS62‐b‐4VP199 results in a diblock copolymer with a weight fraction P4VP of 0.66. It forms a remarkably well‐ordered lamellar structure. Likewise, a tBOS146‐b‐4VP120 diblock copolymer with a weight fraction P4VP of 0.33 forms an extremely well‐ordered hexagonal structure of P4VP cylinders. Increasing the P4VP block of this block copolymer to tBOS146‐b‐4VP190 with a weight fraction P4VP of 0.44 results in a bicontinuous gyroid morphology despite the estimated strong segregation of . These results are discussed in terms of the architectural dissimilarity of the two monomers, characterized by the presence of the large side group of PtBOS, and the previously reported value of the interaction parameter, , for this polymer pair.
Block copolymer (BCP) self‐assembly is a versatile technique in the preparation of polymeric aggregates with varieties of morphologies. However, its morphology library is limited. Here, the discovery of pincushion of tubules is reported for the first time, via BCP self‐assembly of poly(4‐vinylpyridine)‐b‐polystyrene (P4VP‐b‐PS) with very high molecular weight (500 kDa) and asymmetry (2 mol% P4VP). The investigation confirms the importance of core‐forming block length on morphology control of BCP self‐assemblies, especially with respect to tubular structures. The morphology landscape of tubular structures is successfully established, where dumbbell of tubule, tubule, loose clew of tubules, tight clew of tubules, and pincushion of tubules can be prepared by adjusting the core‐forming block length. This work therefore expands the structure library of BCP self‐assemblies and opens up a new avenue for the further applications of these tubular materials. 相似文献
Summary: The complexation between polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) micelles and poly(ethylene glycol)‐block‐poly(4‐vinyl pyridine) (PEG‐b‐P4VP) is studied, and a facile strategy is proposed to prepare core‐shell‐corona micellar complexes. Micellization of PS‐b‐PAA in ethanol forms spherical core‐shell micelles with PS block as core and PAA block as shell. When PEG‐b‐P4VP is added into the core‐shell micellar solution, the P4VP block is absorbed into the core‐shell micelles to form spherical core‐shell‐corona micellar complexes with the PS block as core, the combined PAA/P4VP blocks as shell and the PEG block as corona. A model is suggested to characterize the core‐shell‐corona micellar complexes.
Schematic formation of core‐shell‐corona (CSC) micellar complexes by adsorption of PEG‐b‐P4VP into core‐shell PS‐b‐PAA micelles. 相似文献
Highly porous polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer membranes are prepared using carbohydrates as additives. Therefore α‐cyclodextrine, α‐(D )‐glucose, and saccharose (cane sugar) are tested for the membrane formation of three different PS‐b‐P4VP polymers. The addition of the carbohydrates leads to an increasing viscosity of the membrane solutions due to hydrogen bonding between hydroxyl groups of the carbohydrates and pyridine units of the block copolymer. In all cases, the membranes made from solution with carbohydrates have higher porosity, an improved narrow pore distribution on the surface and a higher water flux as membranes made without carbohydrates with the same polymer, solvent ratio, and polymer concentration. 相似文献
A variety of sub‐10 nm nanoparticles are successfully prepared by crosslinking of polystyrene‐b‐poly(1,3‐butadiene) (PS‐b‐PB) and polystyrene‐b‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) block copolymer micelles and inverse micelles. Among them, the core‐crosslinked PS‐b‐PB micelles can self‐assemble into ultrathin (< 10 nm) macroporous (pore size <1 µm) membranes in a facile way, i.e., by simply drop‐coating the particle solution onto a mica surface. No continuous/porous membranes are produced from shell‐crosslinked PS‐b‐PB micelles and both forms of PS‐b‐P4VP micelles. This suggests that the unique structure of the block copolymer precursor, including the very flexible core‐forming block and the glassy corona‐forming block and the specific block length ratio, directly determines the formation of the macroporous membrane.