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1.
The basic method for synthesizing syndiotactic polystyrene‐g‐polybutadiene graft copolymers was investigated. First, the syndiotactic polystyrene copolymer, poly(styrene‐co‐4‐methylstyrene), was prepared by the copolymerization of styrene and 4‐methylstyrene monomer with a trichloro(pentamethyl cyclopentadienyl) titanium(IV)/modified methylaluminoxane system as a metallocene catalyst at 50°C. Then, the polymerization proceeded in an argon atmosphere at the ambient pressure, and after purification by extraction, the copolymer structure was confirmed with 1H‐NMR. Lastly, the copolymer was grafted with polybutadiene (a ready‐made commercialized unsaturated elastomer) by anionic grafting reactions with a metallation reagent. In this step, poly(styrene‐co‐4‐methylstyrene) was deprotonated at the methyl group of 4‐methylstyrene by butyl lithium and further reacted with polybutadiene to graft polybutadiene onto the deprotonated methyl of the poly(styrene‐co‐4‐methylstyrene) backbone. After purification of the graft copolymer by Soxhlet extraction, the grafting reaction copolymer structure was confirmed with 1H‐NMR. These graft copolymers showed high melting temperatures (240–250°C) and were different from normal anionic styrene–butadiene copolymers because of the presence of crystalline syndiotactic polystyrene segments. Usually, highly syndiotactic polystyrene has a glass‐transition temperature of 100°C and behaves like a glassy polymer (possessing brittle mechanical properties) at room temperature. Thus, the graft copolymer can be used as a compatibilizer in syndiotactic polystyrene blends to modify the mechanical properties to compensate for the glassy properties of pure syndiotactic polystyrene at room temperature. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
2.
Abstract
In this work the syndiotactic polystyrene copolymer, poly (styrene-co-p-methylstyrene) was prepared by the copolymerization of styrene and p-methylstyrene with cyclopentadienyltitanium trichloride/methylaluminoxane catalyst. This copolymer was functionalized with silyl-hydride groups. The structure of copolymer and functionalized copolymer were characterized by FT-IR, 1H-NMR and 13C-NMR spectroscopy. The obtained results revealed that the functionalization reaction successfully proceeds at low temperatures. Tethering of half-titanocene complex on polymeric support was done by the hydrosilylation reaction of 1-allylindenyltrichlorotitanium with silyl-hydride functionalized copolymer in the presence of Karstedt catalyst as a coupling reagent. The polymer-supported catalyst was tested for syndiospecific polymerization of styrene using methylaluminoxane as a cocatalyst. The results of styrene polymerization showed that the polymer-supported catalyst exhibited high activity for syndiospecific polymerization of styrene. The polymer prepared with supported catalyst was characterized by carbon nuclear magnetic resonance (13C-NMR) and differential scanning calorimetry (DSC). The results confirmed the syndiotacticity of obtained polymers. X-ray diffraction (XRD) analysis showed the δ-form crystalline structure of obtained syndiotactic polystyrene. 相似文献3.
Doubly thermo-responsive brush-linear diblock copolymers and formation of core-shell-corona micelles
Doubly thermo-responsive brush-linear diblock copolymer of poly[poly(ethylene glycol) methyl ether vinylphenyl]-block-poly(N-isopropylacrylamide) (PmPEGV-b-PNIPAM) is prepared by RAFT polymerization. The obtained brush-linear diblock copolymer exhibits two lower critical solution temperatures (LCSTs) corresponding to the linear poly(N-isopropylacrylamide) (PNIPAM) block and the brush poly[poly(ethylene glycol) methyl ether vinylphenyl] (PmPEGV) block in water. This brush-linear diblock copolymer undergoes a two-step temperature sensitive micellization. At temperature above the first LCST, the brush-linear diblock copolymer self-assembles into core-corona micelles with the dehydrated PNIPAM block forming the core and the solvated brush PmPEGV block forming the corona. When temperature increases above the second LCST, the polystyrene backbone in the brush PmPEGV block collapses onto the dehydrated PNIPAM core to form core-shell-corona micelles, in which the dehydrated PNIPAM block forms the core, the collapsed polystyrene backbone in the brush PmPEGV block forms the shell and the solvated poly(ethylene glycol) side-chains forms the corona. The effect of the length of the PNIPAM block and the length of the poly(ethylene glycol) side-chains on the thermo-responsive micellization and the size of core-shell-corona micelles is investigated. 相似文献
4.
Ayesha Kausar 《Polymer-Plastics Technology and Engineering》2015,54(17):1794-1802
A block copolymer of polyethylene-block-poly(ethylene glycol) and polycaprolactone was prepared via co-ordination–insertion polymerization. Blend membranes of poly(styrene-block-methyl methacrylate) and polyethylene-block-poly(ethylene glycol)-block-polcaprolactone were used as matrix. Gold/polystyrene nanoparticles were used as nanofiller in polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles membranes. The double gyroid pattern was depicted by blend chains in polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles. An improvement of 22% in tensile strength and 54% in tensile modulus was observed with 1 wt% nanoparticle addition. Polyethylene-block-poly(ethylene glycol)-block-polcaprolactone/poly(styrene-block-methyl methacrylate)/gold/polystyrene nanoparticles 1 showed water flux of 45.2 mL cm?2 min?1 and salt rejection ratio of 17.5%. Efficiency of gold nanoparticles–polystyrene nanoparticles reinforced membranes in removal of heavy metal ions was 100%. 相似文献
5.
Functionalized syndiotactic polystyrene copolymers were synthesized and characterized. The syndiotactic polystyrene copolymers, poly(styrene‐co‐4‐methylstyrene) (sPSMS), were prepared by styrene with 4‐methylstyrene with a metallocene/methylaluminoxane catalyst. In addition, grafted copolymers, chemically grafted with isoprene onto an sPSMS backbone [poly(styrene‐co‐4‐methylstyrene)‐g‐polyisoprene (sPSMS‐g‐PIP)] were synthesized by anionic grafting polymerization with a metallation reagent. In this study, we also examined the effect of the degree of functionalization (epoxidation) on the polymer structure of the sPSMS‐g‐PIP copolymers. Experimental results indicate that the crystallinity of the sPSMS‐g‐PIP copolymer was lower than that of the ungrafted sPSMS copolymer. Moreover, the epoxy‐containing sPSMS‐g‐PIP copolymer effectively increased the thermal stability more than did the sPSMS‐g‐PIP copolymer alone. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1038–1045, 2002 相似文献
6.
Crosslinked polystyrene ethylene glycol acrylate resin (CLPSER) was developed for the immobilization of the enzyme catalase by the introduction of a crosslinker, O,O′‐bis(2‐acrylamidopropyl) poly(ethylene glycol)1900, to styrene. The crosslinker was prepared by the treatment of acryloyl chloride with O,O′‐bis(2‐aminopropyl) poly(ethylene glycol)1900 in the presence of diisopropylethylamine. The resin was characterized with IR and 13C‐NMR spectroscopy. The catalytic activity of the catalase‐immobilized system of CLPSER was compared with divinylbenzene‐crosslinked polystyrene, ethylene glycol dimethacrylate crosslinked polystyrene, and 1,4‐butanediol dimethacrylate crosslinked polystyrene systems. Crosslink levels of 2, 8, and 20 mol % were evaluated. Among these crosslinked systems, the 2 mol % system was found to be most suitable to support catalytic activity. When a long flexible hydrophilic poly(ethylene glycol) crosslink, introduced between the polystyrene (PS) backbone and functional groups was used for immobilization, the extent of coupling and enzyme activity increased. Depending on the nature of the support, the catalytic activity of the system varied. The hydrophilic CLPSER support was most efficient for immobilization compared to the other PS‐based supports. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 8–19, 2005 相似文献
7.
Ester-ether copolymers were prepared by melt condensation reaction using dimethyl terephthalate (DMT) and different quantities of ethylene glycol (EG) and poly(ethylene glycol) (PEG) (MW 400) in the initial monomer feed. Five copolymer samples were prepared by varying the contents of PEG on the basis of EG from 0.5 to 2.5 mol-%. The polymer samples were characterized by determination of melting points (mp) and intrinsic viscosities. The mp decreased from 258°C to 248°C on increasing the poly(ethylene oxide) segments in the backbone. Thermal stability of the copolymers also decreased by the introduction of PEG units in the backbone. The polymers were melt spun into fibres. With the increase of PEG in the copolymer fibres a decrease in tensile strength and initial modulus was observed while the elongation increased. The dye uptake and moisture regain of the copolyester fibres was considerably enhanced in comparison of poly(ethylene glycol terephthalate) (PET) fibres. 相似文献
8.
Hydrophilic hydrogels based on poly(ethylene glycol)–poly(propylene glycol)–poly(ethylene glycol) block copolymers have potential
applications in drug delivery, tissue engineering and other biomedical devices due to their excellent biocompatibility and
environmental sensitivity. However, they also exhibit some shortcomings in terms of swelling and mechanical properties as
well as affinity for water-insoluble or hydrophobic drug molecules. To address these limitations, new polymeric hydrogels
with β-cyclodextrin moieties were prepared by UV photo-polymerization of maleic anhydride-substituted β-CD (MAH-CD) and the block copolymer macromer from Pluronic F68 and poly(ɛ-caprolactone). Their swelling and dynamic rheological
properties were investigated with respect to the effects of feed compositions. It was found that the swelling ratio, storage
modulus and loss modulus of the resulting hydrogel increased with the increase of MAH-CD amount. Incorporation of MAH-CD resulted
in strong viscoelastic system with dominating elastic behavior. 相似文献
9.
Summary A new graft copolymer, poly(ε-caprolactone) (PCL) grafted with poly(ethylene glycol) (PEG), was prepared by one-pot synthesis
of ε-caprolactone and modified PEG. Aluminium isopropoxide or potassium tert-butoxide was used as a catalyst for the ring-opening polymerization. Polymerization using potassium tert-butoxide as a catalyst
showed very effective graft reaction of PEG onto poly(ε-caprolactone). A slight decrease in the melting temperature was observed
with the increase of the PEG graft frequency. Interestingly, considerable changes were observed on the surface property by
the introducing PEG side chains compared to that of PCL homopolymer. Measurements of water contact angle showed that the hydrophilic
surface of the polymer could be obtained even at a low graft frequency of PEG. 相似文献
10.
Reverse atom transfer radical polymerization (RATRP) of styrene (S) was carried out in bulk using polyazoester prepared by
the reaction of polyethylene glycol with molecular weight of 3000 and 4,4′-azobis(4-cyanopentanoyl chloride) as initiator
and CuCl2/2,2′-bipyridine (bpy) catalyst system to yield poly(ethylene glycol-b-styrene) block copolymer. The block copolymers were
characterized 1H NMR, FT-IR spectroscopy and GPC. The 1H NMR, and FT-IR spectra showed that formation of poly(ethylene glycol-b-styrene) block copolymer. The polydispersities of
block copolymers were observed between from 1.49 and 1.98 GPC measurements. 相似文献
11.
A facile synthetic pathway to a multi‐arm star graft polymer has been developed via a grafting‐onto strategy using a combination of a reversible addition–fragmentation chain transfer (RAFT) arm‐first technique and aldehyde–aminooxy click reaction. A star backbone bearing aldehyde groups was prepared by the RAFT copolymerization of acrolein (Ac), an existing commercial aldehyde‐bearing monomer, with styrene (St), followed by crosslinking of the resultant poly(St‐co‐Ac) macro‐RAFT agent using divinylbenzene. The aldehyde groups on the star backbone were then used as clickable sites to attach poly(ethylene glycol) (PEG) side chains via the click reaction between the aldehyde groups and aminooxy‐terminated PEG, leading to a structurally well‐defined star graft copolymer with arms consisting of poly(St‐co‐Ac) as backbone and PEG as side chains. Crystalline morphology and self‐assembly in water of the obtained star graft copolymer were also investigated. Opportunities are open for the star graft copolymer to form either multimolecular micelles or unimolecular micelles via control of the number of grafted PEG side chains. © 2013 Society of Chemical Industry 相似文献
12.
Summary
This paper describes the synthesis and characterization of a new series of copolymers with a predominantly poly(ethylene oxide)
(PEO) backbone and phenyl and/or 4,4'-biphenyl structural units. Three copolymers, poly[oxyethylene]/poly[oxyphenylene] copolymer
(1), poly[oxyethylene] /poly[oxybiphenylene] copolymer (2), and poly[oxyethylene]/poly[oxyphenylene]/poly [oxybiphenylene] copolymer (3), were prepared based on modifications of hydroquinone and/or 4,4'-biphenol copolymerized with dimesylates of various length
poly(ethylene glycol)s (PEGs). Depending on their composition and chain length of PEGs used in the polymerization, the copolymers
show liquid crystallinity or non-liquid crystallinity.
Received: 16 November 1999/Revised version: 17 January 2000/Accepted: 27 January 2000 相似文献
13.
Atom transfer radical polymerization was used to synthesize a well-defined poly(ethylene glycol)-b-poly(mercapto ethylacrylamide) (PEG-b-PMEAAm) diblock copolymer. Poly(ethylene glycol)-b-poly[N-(acryloxysuccinimide)](PEG-b-PNAS) was synthesized at 80 °C using methoxy-poly(ethylene glycol)-2-bromo propanoate (PEG-Br) and CuBr/2,2′-bipyridine as
a macroinitiator and catalyst, respectively. The monomer conversion was determined by 1H nuclear magnetic resonance (NMR) spectroscopy. The resulting PEG-b-PNAS diblock copolymer was characterized by gel permeation chromatography, Fourier transform infrared (FT-IR), and 1H NMR spectroscopy. Disulfide groups were introduced by a simple reaction through the N-acryloxysuccinimide (NAS) moieties of the PEG-b-PNAS diblock copolymer with cystamine dihydrochloride in the presence of triethylamine. FT-IR spectroscopy was used to confirm
the introduction of disulfide moieties into the polymer repeating units. Subsequently, a thiol-functionalized block copolymer
was prepared using DL-dithiothreitol (DTT) as the reducing agent and the reduction step was monitored by 1H NMR spectroscopy. This thiol group was transformed easily to a disulfide bond using FeCl3 as an oxidizing agent. The transformation into disulfide could be visualized easily as insoluble polymeric particles formed
from a clear solution of PEG-b-PMEAAm after oxidation. 相似文献
14.
Preparation of a new polymer‐dispersed liquid crystal film by using phthalocyanine‐functional photocurable copolymer
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A new, asymmetrical zinc phthalocyanine (aZnPc)‐functional photocurable copolymer was prepared by the combination of atom transfer radical polymerization and copper (I)‐catalyzed azide‐alkyne cyclo‐addition (CuAAC) click reaction and used as polymer matrix of polymer dispersed liquid crystal (PDLC) film. For this purpose, aZnPc was prepared through statistical condensation of 4‐tert‐butylphthalonitrile and 4‐pent‐4‐ynyloxyphthalonitrile. Double CuAAC click reaction between azido‐functional poly(methyl methacrylate‐co‐2‐(2‐bromoisobutyryloxy)‐ethyl methacrylate), terminal alkynyl‐substituted aZnPc, and 4‐ethynyl‐N,N‐dimethyl aniline yielded photocurable aZnPc‐functional copolymer. Thereby, synthesized copolymer was crosslinked in the presence of liquid crystalline mesogen 4′‐(octyloxy)‐4‐biphenylcarbonitrile by ultraviolet irradiation using benzophenone as initiator and ethylene glycol dimethacrylate as difunctional crosslinker. Thermal and optical properties of PDLC film were investigated by using differential scanning calorimetry and polarized optical microscopy. Smectic A liquid crystal mesophases were observed in both PDLC film and its mesogenic component 4′‐(octyloxy)‐4‐biphenylcarbonitrile. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41574. 相似文献
15.
Hanjia CHEN Xuhua SHI Yafei ZHU Yi ZHANG Jiarui XU 《Frontiers of Chemical Engineering in China》2008,2(1):102-108
A novel macromolecular surface modifier, polypropylene-grafted-poly(ethylene glycol) copolymer (PP-g-PEG), was synthesized by coupling polypropylene containing maleic anhydride with monohydroxyl-terminated poly(ethylene glycol).
The effects of the reaction condition on the graft reactions were studied. The copolymers were characterized by IR, 1H NMR, thermogravimetry (TG) and differential scanning calorimetry (DSC). The results indicated that the graft reactions were
hindered by increasing the molecular weight of PP or PEG. The graft copolymer was found to have a higher initial thermal degradation
temperature and lower crystallization capacity as compared with pure PP, and the side chain of PEG hindered the PP chain from
forming a perfect β crystal. The thermal stability of PP-g-PEG decreased with the increasing content or molecular weight of PEG. The copolymers were blended with polypropylene to modify
the surface hydrophilicity of the products. The results of attenuated total reflectance FTIR spectroscopy (ATR-FTIR) showed
that PP-g-PEG could diffuse preferably onto the surface of the blends and be suitable as an effectual macromolecular surface modifier
for PP.
__________
Translated from Acta Polymerica Sinica, 2007, (2): 203–208 [译自:高分子学报] 相似文献
16.
Polymerization and copolymerization of vinyl monomers such as acrylamide, acrylonitrile, vinyl acetate, and acrylic acid with a redox system of Ce(IV) and organic reducing agents containing hydroxy groups were studied. The reducing compounds were poly(ethylene glycol)s, halogen‐containing polyols, and depolymerization products of poly(ethylene terephthalate). Copolymers of poly(ethylene glycol)s‐b‐polyacrylonitrile, poly(ethylene glycol)s‐b‐poly(acrylonitrile‐co‐vinyl acetate), poly(ethylene glycol)s‐b‐polyacrylamide, poly(ethylene glycol)s‐b‐poly(acrylamide‐co‐vinyl acetate), poly(1‐chloromethyl ethylene glycol)‐bpoly(acrylonitrile‐co‐vinyl acetate), and bis[poly(ethylene glycol terephthalate)]‐b‐poly(acrylonitrile‐co‐vinyl acetate) were produced. The yield of acrylamide polymerization and the molecular weight of the copolymer increased considerably if about 4% vinyl acetate was added into the acrylamide monomer. However, the molecular weight of the copolymer was decreased when 4% vinyl acetate was added into the acrylonitrile monomer. Physical properties such as solubility, water absorption, resistance to UV light, and viscosities of the copolymers were studied and their possible uses are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1385–1395, 1999 相似文献
17.
Amphiphilic block copolymers are macromolecular compounds of great importance from both fundamental scientific and many technological
point of views for a large variety of applications. Amphiphilic diblock copolymer containing segments of monomethoxypoly(ethylene
glycol) and polystyrene (MPEG-b-PS) was synthesised by a convenient method for preparation of macroinitiator MPEG-TEMPO for
‘living’ free radical polymerization (NMRP technique). Initially, derivative of MPEG with chlorine function has been prepared
in an one-step reaction with thionyl chloride. 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-OH) obtained by reduction of
2,2,6,6-tetramethyl-piperidinyl-1-oxy (TEMPO) with sodium ascorbate was coupled with chlorinated MPEG to yield the macroinitiator
MPEG terminated with a TEMPO unit (MPEG-TEMPO), which was further used to prepare the diblock copolymer MPEG-b-PS of styrene.
The product was purified and identified by 1H NMR, GPC and, FT-IR. 相似文献
18.
Well-defined comb-like branched polymers having one branch in each repeating unit have been successfully synthesized by the
coupling reaction of living polystyrene (PS) and polyisoprene (PI) anions with 1, 1-diphenylethenyl (DPE) groups along PS
backbone prepared via atom transfer radical polymerization (ATRP) of 4-vinylbenzyloxy benzophenone (Sc) followed by Wittig
reaction. The resulting comb-like branched polymers were characterized by IR, 1H-NMR, gel permeation chromatography (GPC) and static light scattering (SLS) in detail. The effect of living chains and DPE
group molar ratio on grafting efficiency was discussed. The results show the coupling reaction of living chains and DPE groups
was highly effective, and the coupling efficiency can be controlled via the feed molar ratios of living chains and DPE groups.
Moreover, the effect of molecular weights of backbone (PSe) and PSLi or PILi on grafting efficiency was also discussed. The
results show that when excess living polymers were used, the almost quantitative grafting efficiency could be achieved.
__________
Translated from Acta Polymerica Sinica (China), 2007, (3): 203–208 [译自: 高分子学报] 相似文献
19.
The aim of this study was to demonstrate hydrogen donating capability of poly(ethylene oxide) (PEO) in type II photoinitiated
free radical polymerization for dental applications. Photopolymerization kinetics of the dental resin mixtures were monitored
by Photo-DSC. H-NMR spectroscopic and GPC studies were also performed in order to gain insight to the hydrogen abstraction
mechanism. The effect of molecular weight of PEO on the photoinitiation efficiency was investigated. Photolysis of solutions
containing benzophenone and PEO in the presence of a radical scavenger namely, 2,2,6,6-tetramethylpiperidine-N-oxyl free radical (TEMPO) revealed that photoexcited benzophenone readily abstracts hydrogen from methylene groups present
in PEO backbone. It was demonstrated that such photoinitiating system can be converted to a versatile grafting process. PEO
possessing photochemically attached TEMPO units initiates the nitroxide mediated radical polymerization of styrene upon heating
at 110 °C leading to the formation of poly(ethylene oxide-g-styrene) graft copolymer. Potential use of the photoinitiating system in dental formulations was also demonstrated. The polymeric
nature, water solubility and nontoxicity make PEO a promising candidate as hydrogen donor in dental formulations. 相似文献
20.
In-Il Jung Seungjoo Haam Giobin Lim Jong-Hoon Ryu 《Korean Journal of Chemical Engineering》2011,28(9):1945-1951
Methoxy poly(ethylene glycol)-b-poly(L-lactide) (MPEG-PLLA) diblock copolymer was synthesized via ring-opening polymerization, and MPEG-PLLA microparticles
were then prepared using an aerosol solvent extraction system (ASES) technique with compressed carbon dioxide as antisolvent.
The MPEG-PLLA microparticles were prepared at temperatures ranging from 25 °C to 55 °C and at pressures from 85 bar to 150
bar. The concentration of MPEG-PLLA copolymer, solution flow rate, and CO2 flow rate were adjusted to be 0.5–3.0% (w/v), 0.3–1.0 mL/min, and 19 g/min, respectively. Relatively small spherical microparticles
were prepared in the subcritical region at 25 °C, while agglomerated particles were obtained at temperatures above the critical
point. The mean particle sizes of the MPEGPLLA microparticles prepared by the ASES varied from 9.53 μm to 46.9 μm depending
upon the operating conditions. 相似文献