首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Degradable polyester‐based star polymers with a high level of functionality in the arms were synthesized via the “arms first” approach using an acetylene‐functional block copolymer macroinitiator. This was achieved by using 2‐hydroxyethyl 2′‐methyl‐2′‐bromopropionate to initiate the ring‐opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end‐group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4′‐bioxepanyl‐7,7′‐dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl‐protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide‐functionalized linear polystyrene via a copper (I)‐catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with “brush‐like” arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485–1498, 2009  相似文献   

2.
Hyperbranched polyesters are among the most common hyperbranched polymers. One of the interesting features of hyperbranched polyesters is that they contain unreacted hydroxyl and carboxylic acid groups at the linear and terminal structural units, which can be postmodified to adjust thermal, solubility, or mechanical properties, or to prepare core–shell type architectures. This article reports on the synthesis of a novel class of hyperbranched polyesters via an A2 + B3 type Baylis–Hillman polymerization of 2,6‐pyridinedicarboxaldehyde and trimethylolpropane triacrylate. Baylis–Hillman polymerization generates highly functional polyesters that contain not only unreacted aldehyde and/or acrylate groups at the linear and terminal structural units but also chemically orthogonal vinyl and hydroxyl groups along the polymer backbone. Using 3‐hydroxyquinuclidine as the catalyst, hyperbranched polymers with number‐average molecular weights up to 7500 g/mol and degrees of branching up to 0.81 were obtained. To demonstrate the versatility of these hyperbranched polyesters to act as platforms for further derivatization, the orthogonal postpolymerization modification of the hydroxyl, vinyl, and pyridine functional moieties with phenyl isocyanate, methyl‐3‐mercaptopropionate, and methyl iodide is presented. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.  相似文献   

3.
Radical catalyzed thiol‐ene reaction has become a useful alternative to the Huisgen‐type click reaction as it helps to expand the variability in reaction conditions as well as the range of clickable entities. Thus, direct generation of hyperbranched polymers bearing peripheral allyl groups that could be clicked using a variety of functional thiols would be of immense value. A specifically designed AB2 type monomer, that carries two allyl benzyl ethers groups and one alcohol functionality, was shown to undergo self‐condensation under acid‐catalyzed melt‐transetherification to yield a hyperbranched polyether that carries numerous allyl end‐groups. Importantly, it was shown that the kinetics of polymerization is not dramatically affected by the change of the ether unit from previously studied methyl benzyl ether to an allyl benzyl ether. The peripheral allyl groups were readily clicked quantitatively, using a variety of thiols, to generate an hydrocarbon‐soluble octadecyl‐derivative, amphiphilic systems using 2‐mercaptoethanol and chiral amino acid (N‐benzoyl cystine) derivatized hyperbranched structures; thus demonstrating the versatility of this novel class of clickable hyperscaffolds. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

4.
We designed a trifunctional initiator ( 3 ) containing anthracene, bromide, and OH functionalities and subsequently used as an initiator in atom transfer radical Polymerization (ATRP) of styrene to yield linear polystyrene (PS) with α‐anthracene, OH, and ω‐bromide terminal groups, of which bromide is later transformed into azide to result in the linear anthracene‐, OH‐, and azide‐terminated PS (l‐α‐anthracene‐OH‐ω‐azide‐PS). The copper‐catalyzed azide–alkyne cycloaddition reaction between l‐α‐anthracene‐OH‐ω‐azide‐PS and α‐furan‐protected‐maleimide‐ω‐alkyne linkage, 4 afforded the linear anthracene‐, OH‐, and maleimide‐terminated PS. The cyclization via intramolecular Diels–Alder click reaction of this linear PS and the subsequent conversion of the hydroxyl into bromide resulted in the cyclic PS with one bromide located on the ring, (c‐PS)‐Br. Finally, the c‐PS‐Br was clicked with either well‐defined tetramethylpiperidine‐1‐oxyl‐terminated poly(ethylene glycol) (PEG) or poly(ε‐caprolactone) (PCL) yielding the tadpole polymer, (c‐PS)‐b‐PEG or (c‐PS)‐b‐PCL. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012  相似文献   

5.
Well‐defined ABCD 4‐Miktoarm star‐shaped quarterpolymers of [poly(styrene)‐poly(tert‐butyl acrylate)‐poly(ethylene oxide)‐poly(isoprene)] [star(PS‐PtBA‐PEO‐PI)] were successfully synthesized by the combination of the “click” chemistry and multiple polymerization mechanism. First, the poly(styryl)lithium (PS?Li+) and the poly(isoprene)lithium (PI?Li+) were capped by ethoxyethyl glycidyl ether (EEGE) to form the PS and PI with both an active ω‐hydroxyl group and an ω′‐ethoxyethyl‐protected hydroxyl group, respectively. After these two hydroxyl groups were selectively modified to propargyl and 2‐bromoisobutyryl group for PS, the resulted PS was used as macroinitiator for ATRP of tBA monomer and the diblock copolymer PS‐b‐PtBA with a propargyl group at the junction point was achieved. Then, using the functionalized PI as macroinitiator for ROP of EO monomer and bromoethane as blocking agent, the diblock copolymer PI‐b‐PEO with a protected hydroxyl group at the conjunction point was synthesized. After the hydrolysis, the recovered hydroxyl group of PI‐b‐PEO was modified to bromoacetyl and then azide group successively. Finally, the “click” chemistry between them was proceeded smoothly. The obtained star‐shaped quarterpolymers and intermediates were characterized by 1H NMR, FT‐IR, and SEC in detail. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2154–2166, 2008  相似文献   

6.
Carboxylic acid chloride end‐functionalized all‐aromatic hyperbranched polyesters were prepared from the bulk polycondensation of the AB2 monomer 5‐(trimethylsiloxy)isophthaloyl dichloride. The acid chloride end functionality of the hyperbranched polyester was modified in situ with methanol and yielded methyl ester ends in a one‐pot process. Chain‐end functionalization and esterification were quantitative according to both potentiometric titration and 1H NMR analysis. The signals of 1H and 13C NMR spectra of the esterified hyperbranched polyester were fully assigned from model compounds of the focal, linear, dendritic, and terminal units. The degree of branching and molecular weight averages measured by 1H and 13C NMR spectroscopy and multidetector size exclusion chromatography increased systematically with increasing polymerization temperatures between 80 and 200 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2855–2867, 2002  相似文献   

7.
Aliphatic polyesters bearing pendant alkyne groups were successfully prepared by step‐growth polymerization of different building blocks such as adipic acid and succinic acid in combination with an acetylene‐based diol, 2‐methyl‐2‐propargyl‐1,3‐propanediol, besides 1,4‐butanediol and ethylene glycol. It was demonstrated that the alkyne groups survive the high reaction temperatures (200 °C) in the presence of a radical inhibitor. The alkyne loading has been tuned by the ratio of the different monomers used, up to 25 mol % of alkyne groups. Subsequently, the alkyne groups have been reacted with azides by the copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, a popular type of “click” chemistry. “Click” reactions have been performed quantitatively in the presence of benzyl azide and azide‐terminated poly(ethylene glycol), yielding brush copolymers in the latter case. Kinetic investigations about this click reaction have been performed by means of on‐line Fourier transform mid‐infrared spectroscopy, which was reported for the first time in the field of the click chemistry research. A whole range of functionalized polyesters, based on poly(ethylene succinate) and poly(butylene adipate), is available, the properties of which can be tailored by choosing the appropriate azide compound. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6552–6564, 2008  相似文献   

8.
The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements.  相似文献   

9.
Novel AB2‐type monomers such as 3,5‐bis(4‐methylolphenoxy)benzoic acid ( monomer 1 ), methyl 3,5‐bis(4‐methylolphenoxy) benzoate ( monomer 2 ), and 3,5‐bis(4‐methylolphenoxy)benzoyl chloride ( monomer 3 ) were synthesized. Solution polymerization and melt self‐polycondensation of these monomers yielded hydroxyl‐terminated hyperbranched aromatic poly(ether‐ester)s. The structure of these polymers was established using FTIR and 1H NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 2.0 × 103 to 1.49 × 104 depending on the polymerization techniques and the experimental conditions used. Suitable model compounds that mimic exactly the dendritic, linear, and terminal units present in the hyperbranched polymer were synthesized for the calculation of degree of branching (DB) and the values ranged from 52 to 93%. The thermal stability of the polymers was evaluated by thermogravimetric analysis, which showed no virtual weight loss up to 200 °C. The inherent viscosities of the polymers in DMF ranged from 0.010 to 0.120 dL/g. End‐group modification of the hyperbranched polymer was carried out with phenyl isocyanate, 4‐(decyloxy)benzoic acid and methyl red dye. The end‐capping groups were found to change the thermal properties of the polymers such as Tg. The optical properties of hyperbranched polymer and the dye‐capped hyperbranched polymer were investigated using ultraviolet‐absorption and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5414–5430, 2008  相似文献   

10.
For the purpose of developing model coating systems, it is important to use well‐defined coating precursors. In this work, polyester oligomers were synthesized by controlled ring‐opening polymerization of ε‐caprolactone and 4‐tert‐butyl‐ε‐caprolactone via an activated monomer mechanism. These well‐defined oligomers, including 3‐armed hydroxyl‐functionalized polyesters and perfluoroalkyl‐end‐capped linear polyesters, have been obtained with controlled functionality and low‐molecular weight polydispersity and without the formation of cyclic structures, as demonstrated by MALDI‐ToF MS analyses. The polymer architecture and functionality can be tuned by using different initiating alcohols. These oligomers have been used as precursors to prepare model low surface‐energy polyurethane coatings. Upon the addition of about 1 wt % of fluorine in the polyurethane films, the advancing contact angles for water and hexadecane have been increased to 105° and 78°, respectively; the surface enrichment of fluorinated species has been confirmed by X‐ray photoelectron spectroscopy. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 218–227, 2008  相似文献   

11.
The effect of monomer structure and catalyst on the synthesis of hyperbranched polyesters based on 4,4-(4′-hydroxyphenyl)pentanoic acid has been examined. The nature of the ester group and the catalyst have a significant effect on the molecular weight of the hyperbranched polyester but do not effect the degree of branching for these materials. The fate of the single ester group at the focal point of these hyperbranched macromolecules is probed by the synthesis and polymerization of 13C labeled methyl 4,4-(4′-hydroxyphenyl)pentanoate. Comparison of the molecular weights determined by 1H- or 13C-NMR spectra with those determined by osmometry suggest that intramolecular cyclization does not occur to a significant extent in these systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1627–1633, 1997  相似文献   

12.
In this contribution, we present new reduction‐cleavable hyperbranched disulfide bonds‐containing poly(ester triazole)s with limited intramolecular cyclization, which can be synthesized by the Cu(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) of A2 monomer of dipropargyl 3,3′‐dithiobispropionate and B3 monomer of tris(hydroxymethyl)ethane tri(4‐azidobutanoate). The hyperbranched poly(ester triazole)s possess numerous terminal groups and weight‐average molecular weight up to 20,400 g mol?1 with a polydispersity index in the range 1.57–2.17. The CuAAC introduces rigid triazole units into the backbones of hyperbranched poly(ester triazole)s and reduces intramolecular cyclization, which is proved by topological analysis and 1H NMR spectroscopy. The disulfide bonds on backbones endow the reduction‐cleavable feature to the hyperbranched poly(ester triazole)s at the presence of dithiothreitol. It gives a novel and convenient methodology for the synthesis of reduction‐responsive functional polymer with controlled topologies, and the reduction‐cleavable hyperbranched poly(ester triazole)s with limited intramolecular cyclization are expected to possess potential in the application of stimuli‐responsive anticancer drug nanocarriers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2374–2380  相似文献   

13.
This article describes the synthesis of a new glycerol‐based AB2 type monomer—ethyl{3‐[2‐hydroxy‐1‐(hydroxymethyl)ethoxy]propyl}thioacetate ( 4 ) and its application for the preparation of hyperbranched polyesters. The polycondensation of 4 has been performed over a wide range of catalysts and reaction conditions leading to polymers containing solely primary hydroxyl groups. The polycondensation progress has been monitored by means of 1H NMR. The degree of branching of the polymers showed to be in the range of 0.5 ± 0.03. The obtained polyesters easily undergo hydrolysis or alcoholysis and may be of interest as recycled materials. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3860–3868, 2009  相似文献   

14.
Novel AB2‐type azide monomers such as 3,5‐bis(4‐methylolphenoxy)carbonyl azide (monomer 1) , 3,5‐bis(methylol)phenyl carbonyl azide (monomer 2) , 4‐(methylol phenoxy) isopthaloyl azide (monomer 3) , and 5‐(methylol) isopthaloyl azide (monomer 4) were synthesized. Melt and solution polymerization of these monomers yielded hydroxyl‐ and amine‐terminated hyperbranched polyurethanes with and without flexible ether groups. The structures of theses polymers were established using FT‐IR and NMR spectroscopy. The molecular weights (Mw) of the polymers were found to vary from 3.2 × 103 to 5.5 × 104 g/mol depending on the experimental conditions used. The thermal properties of the polymers were evaluated using TGA and DSC: the polymer obtained from monomer ( 1 ) exhibited lowest Tg and highest thermal stability and the polymer obtained from monomer ( 2 ) registered the highest Tg and lowest thermal stability. All the polymers displayed fluorescence maxima in the 425–525 nm range with relatively narrow peak widths indicating that they had pure and intense fluorescence. Also, the polymers formed charge transfer (CT) complexes with electron acceptor molecules such as 7,7,8,8‐tetracyano‐quino‐dimethane (TCNQ) and 1,1,2,2‐tetracyanoethane (TCNE) as evidenced by UV‐visible spectra. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3337–3351, 2009  相似文献   

15.
The star graft copolymers composed of hyperbranched polyglycerol (HPG) as core and well defined asymmetric mixed “V‐shaped” identical polystyrene (PS) and poly(tert‐butyl acrylate) as side chains were synthesized via the “click” chemistry. The V‐shaped side chain bearing a “clickable” alkyne group at the conjunction point of two blocks was first prepared through the combination of anionic polymerization of styrene (St) and atom transfer radical polymerization of tert‐butyl acrylate (tBA) monomer, and then “click” chemistry was conducted between the alkyne groups on the side chains and azide groups on HPG core. The obtained star graft copolymers and intermediates were characterized by gel permeation chromatography (GPC), GPC equipped with a multiangle laser‐light scattering detector (GPC‐MALLS), nuclear magnetic resonance spectroscopy and fourier transform infrared. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1308–1316, 2009  相似文献   

16.
To explore the possible applications of hyperbranched polymers for modifying linear polyamides, two hyperbranched aromatic polyesters characterized as high Tg polymers possessing phenolic end groups were used in melt mixing with partly aromatic polyamide and commercially available aliphatic polyamide‐6, respectively. Different amounts of both hyperbranched polyesters (from 1 wt % up to 20 wt %) were added to the polyamides, and the influence of these hyperbranched polyesters on the properties of the polyamides was investigated. The hyperbranched polyester based on an AB2 approach was found to be the most effective modifier. A significant increase of the glass transition temperature of the final blend was detected. However, a remarkable reduction of crystallinity as well as complex melt viscosity of those blends was also observed. The use of an A2+B3 hyperbranched polyester as melt modifier for the polyamides was less effective for changing the thermal properties, and the complex melt viscosity of the final material increased since heterogeneous blends were formed. In contrast to that, generally, the addition of the AB2 hyperbranched polyester to the polyamides resulted in homogeneous blends with improved Tg and processability. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3558–3572, 2009  相似文献   

17.
The synthesis and characterization of hyperbranched aromatic poly(ether imide)s are described. An AB2 monomer, which contained a pair of phenolic groups and an aryl fluoro moiety activated toward displacement by the attached imide heterocyclic ring, was prepared. The nucleophilic substitution of the fluoride with the phenolate groups led to the formation of an ether linkage and, subsequently, to the hyperbranched poly(ether imide), which contained terminal phenolic groups. A similar one‐step polymerization involving a monomer that contained silyl‐protected phenols yielded a hyperbranched poly(ether imide) with terminal silylated phenols. The degree of branching of these hyperbranched polymers was approximately 55%, as determined by a combination of model compound studies and 1H NMR integration experiments. End‐capping reactions of the terminal phenolic groups were readily accomplished with a variety of acid chlorides and acid anhydrides. The nature of the chain‐end groups significantly influenced physical properties, such as the glass‐transition temperature and the solubility of the hyperbranched poly(ether imide)s. As the length of the acyl chain of the terminal ester groups increased, the glass‐transition temperature value for the polymer decreased, and the solubility of the polymer in polar solvents was reduced, becoming more soluble in nonpolar solvents. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2536–2546, 2001  相似文献   

18.
Hyperbranched polymers are important soft nanomaterials but robust synthetic methods with which the polymer structures can be easily controlled have rarely been reported. For the first time, we present a one‐pot one‐batch synthesis of polytriazole‐based hyperbranched polymers with both low polydispersity and a high degree of branching (DB) using a copper‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization. The use of a trifunctional AB2 monomer that contains one alkyne and two azide groups ensures that all Cu catalysts are bound to polytriazole polymers at low monomer conversion. Subsequent CuAAC polymerization displayed the features of a “living” chain‐growth mechanism with a linear increase in molecular weight with conversion and clean chain extension for repeated monomer additions. Furthermore, the triazole group in a linear (L) monomer unit complexed CuI, which catalyzed a faster reaction of the second azide group to quickly convert the L unit into a dendritic unit, producing hyperbranched polymers with DB=0.83.  相似文献   

19.
The aliphatic polyurethane with pendant alkyne, perfluorophenyl, and anthracene moieties (PU‐anthracene) was prepared from polycondensation of anthracene, alkyne, and perfluorophenyl functional‐diols with hexamethylenediisocyanate in the presence of dibutyltindilaurate (DBTL) in CH2Cl2 at room temperature for 10 days. Thereafter, the PU‐(anthracene‐co‐alkyne‐co‐perfluorophenyl) (Mn,GPC = 15,400 g/mol, Mw/Mn= 1.37, relative to PS standards) was sequentially clicked with benzyl azide, octylamine, and 4‐(2‐hydroxyethyl)?10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐ene‐3,5‐dione (adduct alcohol) via copper‐catalyzed azide‐alkyne cycloaddition, active ester substitution and Diels–Alder reactions, respectively, to finally yield PU‐(hydroxyl‐co‐benzyltriazole‐co‐octylamine). The PUs were characterized using 1H NMR, GPC, and DSC. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 480–486  相似文献   

20.
A new strategy for the one‐pot preparation of ABA‐type block‐graft copolymers via a combination of Cu‐catalyzed azide‐alkyne cycloaddition (CuAAC) “click” chemistry with atom transfer nitroxide radical coupling (ATNRC) reaction was reported. First, sequential ring‐opening polymerization of 4‐glycidyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (GTEMPO) and 1‐ethoxyethyl glycidyl ether provided a backbone with pendant TEMPO and ethoxyethyl‐protected hydroxyl groups, the hydroxyl groups could be recovered by hydrolysis and then esterified with 2‐bromoisobutyryl bromide, the bromide groups were converted into azide groups via treatment with NaN3. Subsequently, bromine‐containing poly(tert‐butyl acrylate) (PtBA‐Br) was synthesized by atom transfer radical polymerization. Alkyne‐containing polystyrene (PS‐alkyne) was prepared by capping polystyryl‐lithium with ethylene oxide and subsequent modification by propargyl bromide. Finally, the CuAAC and ATNRC reaction proceeded simultaneously between backbone and PtBA‐Br, PS‐alkyne. The effects of catalyst systems on one‐pot reaction were discussed. The block‐graft copolymers and intermediates were characterized by size‐exclusion chromatography, 1H NMR, and FT‐IR in detail. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号