Synthesis and characterization of telechelic polymers obtained by micellar polymerization

Summary The synthesis, characterization and rheological properties in aqueous solution of two telechelic polymers of different structures and size are reported: they are water soluble polyacrylamides, hydrophobically modified with linear and di-substituted hydrophobic initiators. The polymers were prepared via free radical micellar polymerization. The results of static light scattering (SLS), showed similar weight-average molecular weights (M_w) in all of the synthesized polymers. No signal corresponding to the presence of the hydrophobic group of the initiator could be observed by ¹H NMR; however, the presence of these hydrophobic groups was demonstrated using rheological measurements.     

Synthesis,characterization and rheological properties of three different microstructures of water-soluble polymers prepared by solution polymerization

Three different structures were synthesized via solution free radical polymerization. Polyacrylamides hydrophobically modified with small amounts of two different N′N-dialkylacrylamides [N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)] and two different N-alkylacrylamides [N-dodecylacrylamide (DAM) and N-hexadecylacrylamide (HDAM)] have been synthesized using two linear hydrophobic initiators with 12 (ACVA₁₂) and 16 (ACVA₁₆) carbon atoms and two di-substituted hydrophobic initiator with two chains of 6 (ACVA_di6) and 8 (ACVA_di8) carbon atoms derived from 4′4-azobis(4-cyanopentanoic acid) (ACVA). The polymers obtained were telechelic, multisticker and combined. The initiators, monomers and polymers synthesized were characterized by ¹H NMR and light scattering (LS). The rheological properties of these three different associative polymers were investigated using steady-state experiments. The effect of location and structure (linear or di-substituted) of the hydrophobic groups upon the viscosity of the polymer in solution was studied.     

Synthesis,characterization and rheological properties of multiblock associative copolymers by RAFT technique

Polymer Bulletin - Preparation of associating multiblock copolymer electrolytes mediated by radical addition–fragmentation chain transfer (RAFT) technique has been evaluated and reported in...     

Rheological properties of three different microstructures of water-soluble polymers prepared by solution polymerization

Polymer chains consisting of water-soluble polyacrylamides hydrophobically modified with low amount of hydrophobic groups, with varying hydrophobic chain structure (C₁₆ and C_di8) and with varying localization of the hydrophobe along the chain (telechelic, multisticker, and combined polymers) were investigated. The viscoelastic behavior of these associative polymers has been studied in semidilute solutions using steady-flow and oscillatory experiments. The effect of type and localization of the hydrophobic groups on the viscosity of the associative polymer solution was investigated. It can be inferred that the high viscosity presented by these polymers, is due largely to G ₀, which represents the number of associations in the medium at any given time and less so on T _R, which represents the duration time of any given association. On all studied samples, T _R as well as G ₀, were affected by the type (di-substituted or linear) and localization of the hydrophobic groups (telechelic, multisticker, or combined).     

Synthesis and characterization of fluorene end-labeled polymers prepared by nitroxide-mediated polymerization

The fluorene-based alkoxyamine 9-(2,2,6,6-tetramethyl-4-hydroxypiperidinyloxy)fluorene was prepared and investigated as a unimolecular initiator in the nitroxide-mediated polymerization (NMP) of styrene. Reactions performed in either bulk or ethereal solvents at 125 °C generated polymers possessing low polydispersity indices (PDIs) and number average molecular weight (M_n) values close to those anticipated based on monomer-to-initiator ratios. A linear relationship between monomer conversion and M_n values was observed by analysis of reaction aliquots with ¹H NMR and gel permeation chromatography (GPC), while PDI values remained low throughout. Analysis of the polymers by UV–vis spectroscopy indicated that approximately 80% of the polymer chains were labeled with the fluorene chromophore, while fluorescence spectroscopy was used to verify that the fluorene was polymer-bound.     

Structure,surface tension,and rheological behaviors of hydrophobically associative polyacrylamides by self-emulsified microemulsion polymerization

Hydrophobically associating copolymers using acrylamide (AM), acrylic acid (AA), and Styrene (St) as comonomers were successfully prepared by self-emulsified microemulsion polymerization, in which low-molecular-weight AM/AA/St copolymers as surfactant and AM as cosurfactant. The structure and chemical composition of AM/AA/St copolymers were characterized by Fourier transform infrared, nuclear magnetic (NMR), and differential scanning calorimeter. The content of PSt in the copolymers is determined by ¹H nuclear magnetic resonance spectra, suggesting that the self-made polymer surfactant can disperse uniformly the St monomers to improve the copolymerization efficiency. Furthermore, the polymerization mechanism of the self-emulsified microemulsion method is explored preliminarily. During the synthesis of the copolymers, the purified copolymer solution is obtained in one step without using a small molecular emulsifier such as sodium dodecyl sulfate, in order to avoid the complicated post-treatment process of the small molecular emulsifier. The copolymers revealed good hydrophobic association properties and low surface tension.     

Synthesis and rheological properties of an associative star polymer in aqueous solutions

Rheological properties of aqueous solutions and hydrogels formed by an amphiphilic star block copolymer, poly(acrylic acid)-block-polystyrene (PAA₅₄-b-PS₆)₄, were investigated as a function of the polymer concentration (C_p), temperature, and added salt concentration. The water-soluble polymer synthesised by atom transfer radical polymerization (ATRP) was found to form hydrogels at room temperature at polymer concentrations, C_p, over 22 g/L due to the interpolymer hydrophobic association of the PS blocks. Increasing C_p leads to stronger elastic networks at room temperature that show a gel-to-solution transition with increasing temperature. Increase of ionic strength decreases the moduli compared with the pure hydrogel but did not affect the gel-sol transition temperature significantly. Small-angle X-ray experiments showed two distinct scattering correlation peaks for samples above the gelling C_p, which indicates the aggregates formed due to hydrophobic association. Upon heating the intensity of the scattering correlation peaks was found to decrease indicating the loss of the network structure due to thermal motion.     

Synthesis, characterization, and properties of novel phenylene-silazane-acetylene polymers

New phenylene-silazane-acetylene polymers, P1 and P2, have been synthesized using Sonogashira cross-coupling reactions with a new designed ethynyl-ended silylenediamine, N,N′-bis(4-ethynylphenyl)-1,1-diphenylsilylenediamine (1), as the key monomer. This also represents the first example that construction of polymers containing silazane unit with Sonogashira coupling reaction. The structures of monomer and polymers were well characterized. Their thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both polymers had good thermal stability with their temperatures at 5% weight loss (T_d5) being higher than 394 °C under nitrogen and higher than 385 °C in air, respectively. Their char yields at 1000 °C under N₂ were above 70%. The fundamental photophysical properties in solution were also investigated. Both polymers showed fluorescence in ultraviolet region with moderate quantum yields. These polymers had potential to be used as high-temperature resistant resins and light-emitting materials with good thermal stability.     

Star-shaped condensation polymers: Synthesis,characterization, and blend properties

A series of ?-caprolactone linear and star polymers were prepared and characterized in order to determine the effect of the star architecture (i.e., star number and arm length) on the morphology of these semicrystalline polymers. A spherulitic morphology was found in all the polymers investigated. However, for six arm stars containing low degrees of polymerization, it appears that the star core dominates its morphological behavior (presumably due to its relatively high volume fraction). The star core effects, however, are markedly reduced in star polymers were the arms contain higher degrees of polymerization. The impact of the star core was further explored by investigating several poly(?-caprolactone) (PCL):styrene–acrylontrile copolymers (SAN) blends. In all instances, miscible blends were the result because a single compositionally dependent glass-transition temperature (T_g) was observed. A moderate elevation in the T_g of the star-shaped polymers does occur, however, compared to their linear analogs. This effect is presumably due to the inability of the SAN chains to completely mix with all segments of star structure. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of polyurethane/titanium dioxide nanocomposites obtained by in situ polymerization

The development of new polymeric and polymeric based materials is fundamental to meet the market demands. This work aims the synthesis and characterization of polyurethane/titanium dioxide nanocomposite, using low cost commercial raw materials. Nanocomposites were synthesized by in situ polymerization reactions in which titanium dioxide were added in the following proportions, by weight, in relation to the mass obtained from the pure polymer: 0.5, 1.0, 2.0, 3.0, 5.0, 7.0, and 10.0 %. These reactions were based in poli (ε-caprolactone) and 1,6-diisocyanatohexane. The materials were characterized by infrared spectroscopy Fourier transform, scanning electron microscopy, differential scanning calorimetry analysis, thermogravimetric analysis, dynamic mechanical thermal analysis, and UV–Vis spectroscopy. Based on the obtained results it was concluded that the nanocomposites synthesized by in situ polymerization presented, in general, thermal properties (degradation temperature) and mechanical properties higher than the pure polymer.     

Study of three different families of water-soluble copolymers: synthesis, characterization and viscoelastic behavior of semidilute solutions of polymers prepared by solution polymerization

Polymer chains consisting of water-soluble polyacrylamides, hydrophobically modified with low amounts of N,N-dialkylacrylamides (N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)) have been prepared via free radical solution polymerization, using two hydrophobic initiators derived from 4,4′-azobis(4-cyanopentanoic acid) (ACVA) containing long linear chains of 12 (C12) and 16 (C16) carbon atoms. This procedure resulted in polyacrylamides containing hydrophobic groups along the chain as well as at the chain ends. This class of polymers, termed ‘combined associative polymers’, has been studied and compared with the multisticker (with hydrophobic groups along the polymer chain) and telechelic (with hydrophobic groups at the chain ends) associative polymers, which were prepared with DHAM or DOAM and with the hydrophobic initiator (ACVA) modified with alkyl chains of two different lengths. The viscoelastic properties of these different families of associative polymers were investigated using steady-flow and oscillatory experiments. The effect of type, localization and concentration of the hydrophobic groups on the viscosity of the associative polymer solution was investigated. All viscosity curves clearly show two different regimes within the semidilute range: a first unentangled regime where the viscosity increases moderately; and a second entangled regime where the viscosity varies according to a power law, proportional to C⁴. The relaxation time, T_R, and the plateau modulus, G₀, showed relatively high values which increased with the number of carbon atoms in the hydrophobic groups. The combined associative polymer (PAM-co-DHAM/ACVA12) showed relaxation times that remained relatively constant along the concentrations studied, but very high values of G₀.     

Molecular characterization and rheological properties of modified poly(ethylene terephthalate) obtained by reactive extrusion

The use of a tetrafunctional epoxy‐based additive to modify the molecular structure of poly(ethylene terephthalate) (PET) was investigated with the aim of producing PET foams by an extrusion process. The molecular structure analysis and shear and elongation rheological characterization showed that branched PET is obtained for 0.2, 0.3 and 0.4 wt% of a tetrafunctional epoxy additive. Gel permeation chromatography (GPC) analysis led to the conclusion that a randomly branched structure is obtained, the structure being independent of the modifier concentration. The evolution of shear and extensional behavior as a function of molecular weight (M_w), degree of branching, and molecular weight distribution (MWD) were studied, and it is shown that an increase in the degree of branching and M_w and the broadening of the MWD induce an increase in Newtonian viscosity, relaxation time, flow activation energy and transient extensional viscosity, while the shear thinning onset and the Hencky strain at the fiber break decrease markedly.     

Synthesis,characterization and thermal properties of phenylene–disiloxane polymers obtained from catalytic cross‐dehydrocoupling polymerization of bis(dimethylsilyl)benzene isomers and water

Phenylene–disiloxane polymers were prepared from 1,4‐bis(dimethylsilyl)benzene and 1,3‐bis(dimethylsilyl)benzene with water in various ratios by catalytic cross‐dehydrocoupling polymerization. Each isomer showed almost equal reactivity in the polymerization as verified by the analysis of the composition by ¹H NMR. Crystallinity observed in the polymer obtained from the 1,4‐isomer was removed by incorporating a small amount of 1,3‐isomer. © 2001 Society of Chemical Industry     

Thermodynamic and rheological properties of rodlike polymers

Investigations on dilute and concentrated solutions of several rodlike polymers are described. The former includes absolute and intensity fluctuation light scattering, exclusion chromatography and viscometry. The latter includes rheological properties of isotropic and anisotropic solutions. The discussion includes data for four rodlike polymers, each soluble only in strong sulphonic acids. The role of electrostic interactions and molecular association on the properties measured is considered. The similarities and differences of the rheological behaviour with that typically found with flexible chain polymers are pointed out.     

耐温耐盐疏水缔合聚合物的合成及性能评价

以丙烯酰胺(AM)、疏水单体烯丙基十二胺和耐盐单体H-66为原料,通过自由基水溶液聚合制备一种聚丙烯酰胺类聚合物RDTA。通过1H NMR和FTIR表征聚合物结构,通过表观黏度、SEM和流变性能测试研究了RDTA在不同溶液中的缔合效应和该缔合行为随温度变化的影响关系。实验结果表明,RDTA的临界缔合质量分数(W*)在0.25% ~ 0.3%。盐离子对RDTA高分子链的刺激作用能够增强该分子链的结构黏度。弹性模量G′随RDTA质量分数的增加而增大,溶液体系表现出弹性体,体系的空间结构更加密集。70℃、90℃和120℃,170 s-1剪切下,0.5% RDTA在6% NaCl盐溶液中剪切时间 < 300 s时,溶液黏度呈现缓慢上升趋势,说明RDTA在NaCl盐溶液中存在盐刺激RDTA溶液增稠的现象,继续剪切1 h后,剪切剩余黏度仍60 mPa·s以上。     

Synthesis,characterization, and properties of silylene–acetylene preceramic polymers

A series of silylene–acetylene preceramic polymers 3a–e were synthesized by polycondensation reaction of dilithioacetylene with dichlorosilane (H₂SiCl₂) or/and methyldichlorosilane (MeSiHCl₂). Their structures were confirmed by infrared spectra (IR), and ¹H and ²⁹Si NMR spectroscopies. Differential scanning calorimetry (DSC) diagrams show exotherms centered at 200 to 233°C temperature range, attributed to crosslinking reaction of the acetylene and Si? H groups. After thermal treatment, the obtained thermosets 4a–e possess excellent thermal stability. Thermogravimetric analysis (TGA) under nitrogen show the T_d5s (temperature of 5% weight loss) for all the thermosets are above 600°C, and the overall char yields are between 95.62% and 89.67% at 900°C. After pyrolysis at 1200°C, the obtained ceramic residues 5a–e exhibit good thermo‐oxidative stability with final weight retention between 98.76% and 91.66% at 900°C under air. In particular, perhydroploy(silylene)ethynylene 3a , which has the highest Si/C ratio in silylene–acetylene polymers, has the highest char yield, and the derived ceramic material 5a displays the best thermo‐oxidative stability. Based on Scanning electron microscopy and its associated energy‐dispersive X‐ray microanalysis (SEM EDX) and ¹³C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis, ceramic 5a contains the highest SiC content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis, characterization polymerization and antibacterial properties of novel thiophene substituted acrylamide

Ethyl 2-acrylamido-4,5,6,7-tetrahydrobenzo [b] thiophene-3-carboxylate (ETTCA) has been synthesized and its structure has been elucidated by elemental analysis and spectral tools. Free radical polymerization of (ETTCA) has been conducted in several solvents using azobisisobutyronitrile (AIBN) as an initiator. The kinetic parameters of polymerization of the ETTCA were investigated, and it was found that the polymerization reaction follows the conventional free radical scheme. The overall activation energy of polymerization ΔE was determined (ΔE = 45.11 kJ mol⁻¹). The copolymerization of ETTCA with three conventional monomers was carried out in dioxane at 65 °C. The monomer reactivity ratios for the copolymerization of ETTCA with methyl methacrylate (MMA), vinyl acetate (VA) and vinyl ether (VE) were calculated. Thermal stability of the ETTCA polymer and its copolymers were investigated by thermogravimetric analysis. It has been found that the prepared polymer (PETTCA) and its copolymers with VA have moderate biological activity and highly dependent on the copolymer composition.     

疏水改性聚丙烯酰胺的胶束聚合法制备及表征研究进展

综述了近年来HMPAM的胶束聚合法的研究进展,介绍了胶束聚合法的原理和合成条件,包括单体、表面活性剂、引发剂、聚合温度和聚合时间以及HMPAM的相对分子质量及组成的表征方法。     

反相乳液制备缔合型耐盐聚合物及流变性能评价

摘要：以丙烯酰胺（AM）、2-丙烯酰胺-十二烷基磺酸钠（AMC12S）、疏水单体GTE-10为原料,通过反相乳液聚合法制备了一种缔合型耐盐聚合物p(AM/AMC12S/GTE-10)。通过FTIR、1HNMR、SEM、TEM及激光粒度分析仪对其结构和形貌进行表征,并对其流变性能进行评价。结果表明,疏水单体GTE-10成功引入聚合物中,聚合完成后的乳液粒径分布集中且均一,盐的加入使得p(AM/AMC12S/GTE-10)分子聚集态更紧密,形成的空间网络结构更稳定。质量分数为0.7%的p(AM/AMC12S/GTE-10)聚合物水溶液在140 ℃时表现出较好的耐温性能;在120 ℃,170 s-1条件下剪切1 h,在质量浓度为20000 mg/L的NaCl和CaCl2水溶液中分别配制质量分数0.7%的聚合物溶液,其黏度分别为64.7和54.2 mPa·s;触变性能测试表明,聚合物具有较好的剪切恢复性能;黏弹性测试结果表明,盐水条件下储能模量（G′）>损耗模量（G″）,金属离子与苯氧乙烯基发生络合反应,使分子间作用力增强,形成的空间结构更稳定且难被破坏,黏弹性更高。     

Thermal degradation of polymers. XII. Synthesis,polymerization and thermal characterization of polymers of m-N,N-dimethylaminostyrene in nitrogen

The monomer m-N,N-dimethylaminostyrene has been synthesized from acetophenone and homopolymerized and copolymerized with styrene, using 2,2′-azobisisobutyronitrile as free-radical initiator. The polymers have been characterized by thermal analysis (DTA, DSC, and TG). Glass transition temperatures have been measured and activation energies for degradation in nitrogen have been established by a variety of methods for comparative purposes.