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1.
Three series of block copolymers of acrylamide (AM) and styrene (St) as hydrophobic comonomer with varied microstructures were prepared in microemulsion medium by changing feed ratio of monomers, ratio of St to surfactant, and amount of initiator, respectively. The effects of microstructure factors of the amphiphilic block copolymers PAM-b-PSt on their aqueous solution properties were investigated by fluorescence probe technique and surface tension measurement in detail. The experimental results show that the aqueous solution properties of PAM-b-PSt are strongly dependent on their microstructure factors, such as the length and content of PSt hydrophobic blocks in the copolymers and their molecular weight. It was found that the main microstructure factors which effect the hydrophobic association behavior of the copolymer PAM-b-PSt are the length and content of PSt hydrophobic blocks in the copolymer, whereas the hydrophobic association behavior of the copolymer is not affected nearly so much by molecular weight in more dilute regions. At the same time, it was also found that the main microstructure factors which affect the surface activity of the copolymer are the content of PSt hydrophobic blocks in the copolymer and molecular weight, whereas the length of PSt blocks in copolymer does not affect surface activity of the copolymer nearly so much under fixed content of PSt hydrophobic blocks and molecular weight in the copolymer.  相似文献   

2.
Summary: Based on a hydrophilic poly(ethylene oxide) macroinitiator (PEOBr), a novel amphiphilic diblock copolymer PEO‐block‐poly(11‐(4‐cyanobiphenyloxy)undecyl) methacrylate) (PEO‐b‐PMA(11CB)) was prepared by atom transfer radical polymerization (ATRP) using CuCl/1,1,4,7,10,10‐hexamethyltriethylenetriamine as a catalyst system. An azobenzene block of poly(11‐[4‐(4‐butylphenylazo)phenoxyl]undecyl methacrylate) was then introduced into the copolymer sequence by a second ATRP to synthesize the corresponding triblock copolymer PEO‐b‐PMA(11CB)‐b‐PMA(11Az). Both of the amphiphilic block copolymers had well‐defined structures and narrow molecular‐weight distributions, and exhibited a smectic liquid‐crystalline phase over a wide temperature range.

The amphiphilic triblock copolymer synthesized here.  相似文献   


3.
Four-armed amphiphilic block copolymers polystyrene-b-poly(N-isopropyl acrylamide) (PSt-b-PNIPAAM)4 were synthesized by atom transfer radical polymerization (ATRP) in two steps. Star narrow dispersed polystyrene, (PSt-Br)4, with controlled number-average molecular weight was firstly synthesized by ATRP of styrene (St) using pentaerythritol tetrakis (2-bromoisobutyrate) (4Bri-Bu) as four-armed initiator. Then, (PSt-b-PNIPAAM)4 was prepared using (PSt-Br)4 as macroinitiator by ATRP. The structures of (PSt-Br)4 and (PSt-b-PNIPAAM)4 were confirmed by characterization by nuclear magnetic resonance (1H NMR). The apparent viscosity of the four-armed (PSt-b-PNIPAAM)4 was significantly lower than that of the linear PSt-b-PNIPAAM with the same amount of repeat units of PSt and PNIPAAM. The self-assembly behavior of the four-armed amphiphilic block copolymers (PSt-b-PNIPAAM)4 in mixed solution (DMF/H2O) and the lower critical solution temperature (LCST) of the resulting micelles were investigated by scanning electron microscopy (SEM), dynamic light scattering (DLS) and UV-VIS spectroscopy. The results show that the size of the mono-dispersed spherical micelles decreased with the increment of the chain length of PNIPAAM in the block copolymers, while LCST increased.  相似文献   

4.
Organic–inorganic pentablock copolymers have been synthesized via atom transfer radical polymerization (ATRP) of styrene (St) and vinyl acetate (VAc) monomers at 60 °C using CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine as a catalyst system initiated from boromoalkyl-terminated poly(dimethylsiloxane) (PDMS)/cyclodextrins macroinitiator (Br-PDMS/γ-CD). Br-PDMS-Br was reacted with γ-CD in different conditions with inclusion complexes being characterized through hydrogen nuclear magnetic resonance (1H NMR) and differential scanning calorimetry (DSC). Resulting Br-PDMS-Br/γ-CD inclusion complexes were taken as macroinitiators for ATRP of St and VAc. Well-defined poly(styrene)-b-poly(vinyl acetate)-b-poly(dimethylsiloxane/γ-cyclodextrin)-b-poly(vinyl acetate)-b-poly(styrene) (PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt) pentablock copolymer was characterized by 1H NMR, gel permeation chromatograph (GPC) and DSC. There was a good agreement between the number-average molecular weight calculated from 1H NMR spectra and that of theoretically calculated. Pentablock copolymers consisting of Br-PDMS-Br/γ-CD inclusion complex as central blocks (inorganic block) and PVAc and PSt as terminal blocks were synthesized by this technique. PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt pentablock copolymer can undergo a temperature-induced reversible transition upon heating of the copolymer complex from white complex at 22 °C to green complex in 55 °C which characterized with XRD and 1H NMR. XRD showed a change in crystallinity percent of St peak with changing the temperature which calculated by Origin75 software.  相似文献   

5.
AB block copolymers of 2‐(2′,3′,4′,6′‐tetra‐O‐acetyl‐β‐D‐glucopyranosyloxy)ethyl acrylate (AcGEA) with styrene (St) have been synthesized by atom transfer radical polymerization using well‐defined bromo‐terminated polystyrene as a macroinitiator. An O‐deacetylation of the precursor copolymers affords amphiphilic block copolymers, PSt‐b‐PGEA, with well‐defined glycopolymer segments and narrow molecular weight distributions (Mw/Mn < 1.4). The examination of the aqueous solution of these amphiphilic block copolymers revealed the formation of ordered aggregates.  相似文献   

6.
Pyridyldisulfide (PDS) functionalized telechelic polymers of oligo(ethyleneglycol) acrylate (PEG‐A) and their amphiphilic triblock copolymers with styrene (St) were synthesized directly by reversible addition‐fragmentation chain transfer (RAFT) polymerization using a new bifunctional RAFT agent, S,S‐bis[α,α′‐dimethyl‐α″‐(2‐pyridyl disulfide) ethyl acetate] trithiocarbonate (BDPET). The homopolymerization of PEG‐A was found to be well controlled using BDPET (PDI < 1.2). The ABA triblock copolymers poly(PEG‐A)‐b‐poly(St)‐b‐poly(PEG‐A) with narrow molecular weight distribution (PDI < 1.25) were synthesized using poly(PEG‐A) as a macro‐RAFT agent. UV‐vis spectroscopic analysis revealed that 85 mol % of poly(PEG‐A) and 78 mol % of poly(PEG‐A)‐b‐poly(St)‐b‐poly(PEG‐A) retained PDS end group functionality. Micelles were observed to form from poly(PEG‐A)‐b‐poly(St)‐b‐poly(PEG‐A). The presence of PDS groups within the micelle corona was evidenced by UV‐vis spectroscopy and fluorescence spectroscopy. The PDS groups within the corona were then used to functionalize the micelles with a thiol group bearing model peptide, reduced glutathione, and a thiol modified fluorophore, rhodamine B, under mild reaction conditions. UV‐vis and fluorescence spectrocopies revealed that approximately 80% PDS groups from the amphiphilic copolymer were tethered within the micelle coronas and accessible to glutathione and fluorophore attachment. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 899–912, 2009  相似文献   

7.
王延梅 《高分子科学》2013,31(4):691-701
A series of double-hydrophilic double-grafted PMA-g-PEG/PDMA copolymers, which contained poly(methacrylate) (PMA) as backbone, poly(ethylene glycol) (PEG) and poly(N,N-dimethylacrylamide) (PDMA) as side chains synthesized successfully by using reversible addition-fragmentation chain transfer (RAFT) polymerization and atom transfer radical polymerization (ATRP), were used as physical coatings for the evaluation of protein-resistant properties by capillary electrophoresis (CE). Electroosmotic flow (EOF) measurement results showed that the PMA-g-PEG/PDMA copolymer coated capillaries could suppress electroosmotic mobility in a wide pH range (pH = 2.8–9.8) and EOF mobility decreased with the increase of copolymer molecular mass and PDMA content. At the same time, protein recovery, theoretical plate number of separation and repeatability of migration time demonstrated that antifouling efficiency was improved with the increase of molecular mass and PEG content.  相似文献   

8.
Well-defined amphiphilic block copolymers composed of hydrophilic and hydrophobic blocks linked through an acid-labile acetal bond were synthesized directly by RAFT polymerization using a new poly(ethylene glycol) (PEG) macroRAFT agent modified with an acid-labile group at its R-terminal. The new macroRAFT agent was used for polymerization of poly(t-butyl methacrylate) (PtBMA) or poly(cholesterol-methacrylate) (PCMA) to synthesize well-defined block copolymers with a PEG block sheddable under acidic conditions. The chain extension polymerization kinetics showed known traits of RAFT polymerization. The molecular weight distributions of the copolymers prepared using the new macroRAFT agent remained below 1.2 during the polymerizations and the molecular weight of the copolymers was linearly proportional to monomer conversions. The acid-catalyzed hydrolysis behavior of the PEG-macroRAFT agent and the PEG-b-PtBMA (Mn = 13,600 by GPC, PDI = 1.10) was studied by GPC, 1H NMR and UV–vis spectroscopy. The half-life of acid-hydrolysis was 70 min at pH 2.2 and 92 h at pH 4.0. The potential use of the pH-labile shedding behavior of the copolymers was demonstrated by conjugating a thiol-modified siRNA to ω-pyridyldisulfide modified PEG-b-PCMA. The resultant PEG-b-PCMA-b-siRNA triblock modular polymer released PCMA-b-siRNA segment in acidic and siRNA segment in reductive conditions, as confirmed by polyacrylamide gel electrophoresis.  相似文献   

9.
Photografting copolymerization of maleic anhydride (MAH) and styrene (St) onto LDPE film was investigated by using a one-step method, and further thermally induced grafting copolymerization of them was carried out by using a two-step method. Regarding the photografting copolymerization of MAH/St binary monomer system, both conversion percentage (CP) and grafting efficiency (GE) increased with raising the content of MAH in the monomer feed. In addition, the content of MAH in the grafted copolymers also increased with increasing the fraction of MAH in the monomer feed. The formation of LDPE-g-P(MAH-co-St) grafted film was identified by FTIR and ESCA spectroscopy. In the case of grafting copolymerization of MAH/St by the two-step method, grafting copolymerization proceeded slowly compared with the non-grafting copolymerization. The apparent activation energy (Ea) for the non-grafting copolymerization in the solution and the grafting copolymerization on LDPE film was 24 and 82 kJ/mol, respectively, which were noticeably lower than those of MAH/vinyl acetate (MAH/VAC) binary monomer system under the similar grafting conditions. These data of Ea explained why the grafting copolymerization of styrene/MAH took place faster than that of MAH/VAC binary monomer system. The composition of the grafted copolymer chains was largely affected by the composition of the monomer feeds; however, the composition of the non-grafted copolymers nearly remained at 1/1 even in systems with largely different MAH/styrene ratios in monomer feeds. It is indicated that the non-grafting copolymerization proceeded predominantly following alternating copolymerization, but the grafting copolymerization performed random copolymerization.  相似文献   

10.
In this work,a new type of block polymers,polystyrene-b-poly[(N-isopropyl acrylamide)-co-(vinyl benzyl chloride)](PS-b-P(NIPAM-co-VBC)),was prepared via reversible addition fragmentation transfer polymerization,then pentacyano(4-(dimethylamino pyridine))ferrate(Fe-DMAP) was attached to VBC units through a quaternization process.The Fe(Ⅱ)-coordinated PS-b-P[NIPAM-co-(VBC-Fe-DMAP)]block copolymers were characterized by ~1H-NMR,FT-IR and TGA.The self-assembly behavior of the block copolymers was also investigated and the micelle morphology was characterized by TEM.It was found that the PS-b-P(NIPAM-co-VBC) block polymer and Fe-coordinated block copolymer could both form spherical micelles in DMF/MeOH mixed solvent.  相似文献   

11.
We have newly synthesized amphiphilic block copolymers composed of hydrophilic poly(ethylene glycol) (PEG) and hydrophobic pyridine segments (PEG-b-Py). Chain transfer agent-terminated PEG was subsequently chain-extended with 3-(4-pyridyl)-propyl acrylate to obtain PEG-b-Py by reversible additional-fragmentation chain transfer polymerization. Particularly, the effect of varying molecular weight (Mn) of PEG (Mn?=?2,000 and 5,000) and Py in the block copolymers was investigated in terms of critical micelle concentration, pyrene solubilization, micelle size distribution, and association number per micelle. Based on the amphiphilic balance, PEG-b-Pys formed core-shell type polymer micelle. The association number of PEG2k-b-Py was higher than that of PEG5k-b-Py, suggesting the degree of phase separation strongly depended on PEG Mn. Furthermore, the adsorption of PEG-b-Py copolymer onto silica nanoparticles as dispersant was studied to estimate the effect of PEG Mn in the copolymers and their solubility in the medium on the adsorption. Adsorbed density of PEG2k-b-Py copolymer onto silica nanoparticle was higher than that of PEG5k-b-Py, which was significantly correlated with the degree of phase separation. Furthermore, the adsorbed amount of copolymer increased with the increase in ionic strength due to the reduced solubility of PEG in the buffer solution. The resultant dispersion stability was highly correlated with the graft density of copolymer onto silica surface. However, the stability of PEG2k-b-Py coated particles was lower than that with PEG5k-b-Py, this is attributed to the relatively thin layer of PEG at the silica surface, which cannot provide the system with sufficient steric stabilization as the salt concentration increases. These fundamental investigations for the surface modification of the nanoparticle provide the insight into the highly stable colloidal dispersion, particularly in the physiological condition with high ionic strength.  相似文献   

12.
New block copolymers with narrow molecular weight distribution based on (2,3-epithiopropylmethacrylate) (ETMA), methylmethacrylate (MMA) and n-butylmethacrylate (nBMA) have been successfully synthesized via reversible addition-fragmentation transfer (RAFT) polymerization. First, RAFT homopolymerization of ETMA and MMA was carried out using 2-(2-cyanopropyl) dithiobenzoate (CPDB) as the chain transfer agent (CTA) and 2,2-azobisisobutyronitrile (AIBN) as the initiator. PETMA-b-P(nBMA) copolymers were synthesized using PETMA homopolymers as the macro-chain transfer agent (MCTA), while PMMA-b-PETMA diblock copolymers were synthesized using PMMA as the MCTA. The evolution of the molecular weight and molecular weight distribution of the homo- and co-polymers were compatible with the RAFT polymerization features. Thin films from the block copolymers were prepared by spin coating a 1 wt% polymer solution from toluene, chloroform or THF. After the preparation, the films were annealed under 80% vapor pressure of chloroform for 1, 2 and 4 h and investigated with scanning electron microscopy (SEM). The most interesting results were found in the films prepared using PETMA-b-P(nBMA) copolymers (). The observed images suggested the formation of hybrid lamellar structures, ascribed to the combination of its higher molecular weight and solvents viscosity.  相似文献   

13.
RAFT copolymerization of beta‐pinene and maleic anhydride was successfully achieved for the first time, using 1‐phenylethyl dithiobenzoate as chain transfer agent in a mixed solvent of tetrehydrofuran and 1.4‐dioxane (1:9, v/v) at a feed molar ratio of beta‐pinene to maleic anhydride as 3:7, and the alternating copolymer was prepared with predetermined molecular weight and narrow molecular weight distribution. Furthermore, using former alternating copolymer as a macro‐RAFT agent, block copolymer poly(beta‐pinene‐alt‐maleic anhydride)‐b‐polystyrene was synthesized in a chain extending with styrene. Hydrolysis of this block copolymer under acidic conditions formed a new amphiphilic block copolymers poly(beta‐pinene‐alt‐maleic acid)‐b‐polystyrene whose self‐assembly behaviors in aqueous solution at different pH were investigated through SEM and DLS. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1422–1429  相似文献   

14.
The star-shaped organic/inorganic hybrid poly(l-lactide) (PLLA) based on polyhedral oligomeric silsesquioxane (POSS) was prepared using octa(3-hydroxypropyl) polyhedral oligomeric silsesquioxane as initiator via ring-opening polymerization (ROP) of l-lactide (LLA). The molecular weight of POSS-containing star-shaped hybrid PLLA (POSSPLLA) can be well controlled by the feed ratio of LLA to initiator. The POSSPLLA was further functionalized into the macromolecular reversible addition-fragmentation transfer (RAFT) agent for the polymerization of N-isopropylacrylamide (NIPAM), leading to the POSS-containing star-shaped organic/inorganic hybrid amphiphilic block copolymers, poly(l-lactide)–block–poly(N-isopropylacrylamide) (POSS(PLLA–b–PNIPAM)). The self-assembly behavior of POSS(PLLA–b–PNIPAM) block copolymers in aqueous solution was investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). DLS showed the PNIPAM block in the aggregates is temperature-responsive and its phase-transition is reversible. TEM proved that the star-shaped POSS(PLLA–b–PNIPAM) amphiphilic block copolymers can self-assemble into the vesicles in aqueous solution. The vesicular wall and coronas are composed of the hydrophobic POSS core and PLLA, and hydrophilic PNIPAM blocks, respectively. Therefore, POSSPLLA and POSS(PLLA–b–PNIPAM) block copolymers, as a class of novel organic–inorganic hybrid materials with the advantageous properties, can be potentially used in biological and medical fields.  相似文献   

15.
Gold nanoparticles by using the mixture of polystyrene-block-poly(2-vinyl pyridine)/poly(2-vinyl pyridine)-block-poly(ethylene oxide) (PS-b-P2VP/P2VP-b-PEO) block copolymers as encapsulating agent was prepared. The prepared nanoparticles were characterized by transmission electron microscopy, UV-Vis spectroscopy and contact angle. It is demonstrated that the obtained gold nanoparticles are covered with mixed block copolymer shells. The hydrophilic property of the nanoparticles can be varied by the change of the dispersion medium. The obtained gold nanoparticles with mixed block copolymer shells are stable in organic solvents (such as tetrahydrofuran and toluene) and water.  相似文献   

16.
Block copolymers constitute a fascinating class of polymeric materials that are used in a broad range of applications. The performance of these materials is highly coupled to the physical and chemical properties of the constituting block copolymers. Traditionally, the composition of block copolymers is obtained by 1H NMR spectroscopy on purified copolymer fractions. Specifically, the integrals of a properly selected set of 1H resonances are compared and used to infer the number average molecular weight (Mn) of one of the block from the (typically known) Mn value of the other. As a corollary, compositional determinations achieved on imperfectly purified samples lead to serious errors, especially when isolation of the block copolymer from the initial macro initiator is tedious. This investigation shows that Diffusion Ordered NMR Spectroscopy (DOSY) can be used to provide a way to assess the advancement degree of the copolymerization purification/reaction, in order to optimize it and hence contribute to an improved compositional analysis of the resulting copolymer. To this purpose, a series of amphiphilic polystyrene-b-poly(ethylene oxide) block copolymers, obtained by controlled free-radical nitroxide mediated polymerization, were analyzed and it is shown that, under proper experimental conditions, DOSY allows for an improved compositional analysis of these block copolymers.  相似文献   

17.
The effect of microstructure on the aggregation behaviour of symmetrical di- and triblock copolymers P(BMA)-b-P(MAA) and P(BMA)-b-P(BMA-co-MAA)-b-P(MAA) with a molecular weight of 40,000 g/mol was studied. The critical micelle concentration, hydrodynamic radius and morphology of the micelles were determined by fluorescence spectroscopy, dynamic light scattering and scanning force microscopy (SFM). Whereas no effect of the microstructure on the critical micelle concentration could be detected, the hydrodynamic radius decreased from di- to triblock copolymer from 53 to 36 nm. The decrease of about 32% corresponds to the length of the random middle block within the triblock copolymer so that the reduction in hydrodynamic radius was caused by a complete orientation of the random middle block at the core corona interface. Finally, the SFM investigation showed that dehydration of micelles on a substrate is accompanied by formation of a physisorbed monolayer with a thickness of 2 nm on which the micelles are deposited.  相似文献   

18.
The double hydrophilic block copolymer poly(ethylene glycol mono-methyl ether)-block-poly(4-vinylpyridine) (mPEG43-b-P4VP115) was synthesized by atom transfer radical polymerization. The structure, molecular weight and molecular weight distribution of mPEG43-b-P4VP115 were characterized by 1H-NMR and gel permeation chromatography combined with laser light scattering technique. The complex micelles based on mPEG43-b-P4VP115 and the disodium 2-naphthol-3,6-disulfonate were obtained in acid aqueous solution. The morphologies of the complex micelles were observed by transmission electron microscopy. The revertible temperature and pH-responsive behaviors of complex micelles were studied by dynamic light scattering and fluorescence techniques.  相似文献   

19.
The diblock copolymers of polystyrene and poly(tert‐butyl acrylate) (PSt‐b‐PtBA) with various molecular weights and hydrophobic/hydrophilic (styrene/acrylic acid) chain length were prepared by atom transfer radical polymerization (ATRP). Selective hydrolysis of the diblock copolymers (PSt‐b‐PtBA) resulted in amphiphilic block copolymers of polystyrene and poly(acrylic acid) (PSt‐b‐PAA). The amphiphilic block copolymers of PSt‐b‐PAA with average molecular weight (Mn) <7500 were proved to be critical in dispersing the pigments of UV curable ink‐jet inks for manufacturing the color filter. Incorporating DB2 diblock copolymer dispersants with styrene/acrylic acid ratio at 1.5 allowed more UV curable compositions in the red and blue inks without deteriorating pigment dispersing stability and jetting properties of the ink‐jet inks. The ink drops can be precisely ejected into the tiny color area. Better properties of the cured red stripe such as nanoindentation hardness and chemical resistance were found. The competing absorption of UV light by the blue pigment hindered the through cure of monomers near the interface between glass substrate and the blue stripe. This leads to lower hardness and poor chemical resistance of the UV cured blue stripe. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3337–3353, 2005  相似文献   

20.
Complexation ability of poly(2-(dimethylamino)ethyl methacrylate)-b-poly(hydroxy propyl methacrylate) (PDMAEMA-b-PHPMA) amphiphilic doubly thermo-responsive block copolymers, and their quaternized counterparts QPDMAEMA-b-PHPMA, toward bovine serum albumin (BSA) is studied in aqueous solutions. The PDMAEMA-b-PHPMA amphiphilic block copolymers self-assemble in nanostructured aggregates with PDMAEMA coronas having different inner structure and micro-polarity depending on the solubilization protocol utilized when inserted in aqueous media. By incorporating different BSA concentrations, we investigate the copolymer–protein interactions by light scattering measurements in aqueous solutions in a broad temperature range, utilizing different solubilization protocols for the copolymers. Fluorescence spectroscopy and ζ-potential measurements were also utilized to investigate the structure and properties of the copolymer/protein complexes formed in each case. Such knowledge may lead to a better understanding of the inner structure and micro polarity of the nanostructured aggregates formed by the novel (Q)PDMAEMA-b-PHPMA copolymers, along with their potential abilities in nanocarrier formation, protein complexation, stabilization, and delivery.  相似文献   

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