Studies on Interaction of Hydrophobically Modified Polyacrylamide of a New Family with Cationic Gemini Surfactant

A new family of hydrophobically modified polyacrylamides (HMPAM) was synthesized via homogeneous copolymerization of acrylamide (AM) and anionic surface-active monomer of acrylamide-type, sodium 2-acrylamido-tetradecane sulfonate (NaAMC₁₄S) in aqueous solution. The copolymers NaAMC₁₄S/AM with microblock structures and with different chain microstructures were obtained by varying the copolymerization factors, such as the feed ratio of NaAMC₁₄S to AM and the amount of added electrolyte NaCl and initiator. The interaction between copolymers NaAMC₁₄S/AM and cationic gemini surfactants, C₁₂C₃C₁₂Br₂ and C₁₂C₆C₁₂Br₂, was studied by using viscosimetry and fluorescent probe technique. The results show this new family of HMPAM, NaAMC₁₄S/AM, has very strong interaction with gemini surfactants, and their aqueous solutions exhibit unique rheological properties.     

Synthesis and Characterization of Surfactant PEG Macromonomers with Fluorocarbon End‐capped Groups and its Copolymers

Fluorocarbon (R_F) or hydrocarbon (R_H) end‐capped PEG macromonomers were prepared by coupling method. Several factors mat affect the synthesis were studied and optimum condition was obtained. The critical micelle concentrations (CMC) of these macromonomers were determined by fluorescence method. A new type of fluorocarbon‐containing hydrophobically modified alkali swellable/soluble copolymers were obtained by copolymerization of R_F or R_H alkyl endcapped PEG macromonomers with acrylic acid in organic solvent The preliminary researches on viscosity property of these copolymer solutions were conducted under different conditions, such as various macromonomer content in the copolymer, polymer concentration, shear rate, pH value and temperature. All the results proved that there existed a very strong hydrophobic association among hydrophobes in these copolymer solutions.     

Compositional heterogeneity effects in multisticker associative polyelectrolytes prepared by micellar polymerization

An aqueous micellar radical polymerization technique has been used to prepare water‐soluble polyelectrolytes of acrylamide (AM) and sodium 2‐acrylamido‐2‐methylpropanesulfonate (NaAMPS) hydrophobically modified with low amounts (2–4 mol %) of N,N‐dihexylacrylamide (DiHexAM). This synthesis method leads to multisticker polymers, in which the number and length of the hydrophobic blocks vary with the degree of conversion. Kinetic studies show an appreciable compositional heterogeneity for these polymers, in contrast to their neutral analogues (i.e., AM/DiHexAM copolymers). The drift in composition observed for the AM/NaAMPS/DiHexAM terpolymers is attributed to the electrostatic repulsion between the negatively charged growing polymeric chains, located in the aqueous continuous medium, and the anionic sodium dodecyl sulfate micelles, inside of which the hydrophobic monomer is entrapped. It is shown that an optimization of the polymerization process can be achieved, which gives terpolymers of homogeneous and well‐defined compositions. The thickening ability of the hydrophobically modified polyelectrolytes is directly affected by the extent of their compositional heterogeneity: an increase in the sample homogeneity leads to a significant viscosity enhancement and marked elastic properties of the polymer solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3261–3274, 2003     

Microstructure and association property of hydrophobically modified polyacrylamide of a new family

A new family of hydrophobically modified polyacrylamides was synthesized via copolymerization of acrylamide (AM) and anionic surface-active monomer of acrylamide-type, sodium 2-acrylamido-tetradecane sulfonate (NaAMC₁₄S), in aqueous solution. In the copolymerization, by varying various factors, such as the feed ratio of NaAMC₁₄S to AM and the amount of added electrolyte NaCl and initiator, we prepared copolymers NaAMC₁₄S/AM with different block structures. The relationship between structures and hydrophobic association properties of copolymer chains was studied by using fluorescence probe and viscosimetry. Effects of the content and length of the hydrophobic blocks and the total molecular weight on hydrophobic association of the copolymers in pure water and in brine solution were examined, respectively. The results show that in pure water, hydrophobic association of the copolymers was enhanced as the content and length of the hydrophobic block increase. On the other hands, for a given content and length of the hydrophobic block, the hydrophobic association of the copolymers was enhanced as the total molecular weight increases. For all the copolymers studied, the apparent viscosity of their solutions in pure water has a limited value, but the apparent viscosities of the copolymer brine solutions are much higher than that of their corresponding water solutions, and show strong positive salinity sensitivity. Similarly, the hydrophobic association of the copolymer in brine solutions was enhanced as the content and length of the hydrophobic block increase.     

Novel temperature‐ and pH‐responsive graft copolymers composed of poly(L‐glutamic acid) and poly(N‐isopropylacrylamide)

A series of novel temperature‐ and pH‐responsive graft copolymers, poly(L ‐glutamic acid)‐g‐poly(N‐isopropylacrylamide), were synthesized by coupling amino‐semitelechelic poly(N‐isopropylacrylamide) with N‐hydroxysuccinimide‐activated poly(L ‐glutamic acid). The graft copolymers and their precursors were characterized, by ESI‐FTICR Mass Spectrum, intrinsic viscosity measurements and proton nuclear magnetic resonance (¹H NMR). The phase‐transition and aggregation behaviors of the graft copolymers in aqueous solutions were investigated by the turbidity measurements and dynamic laser scattering. The solution behavior of the copolymers showed dependence on both temperature and pH. The cloud point (CP) of the copolymer solution at pH 5.0–7.4 was slightly higher than that of the solution of the PNIPAM homopolymer because of the hydrophilic nature of the poly(glutamic acid) (PGA) backbone. The CP markedly decreased when the pH was lowered from 5 to 4.2, caused by the decrease in hydrophilicity of the PGA backbone. At a temperature above the lower critical solution temperature of the PNIPAM chain, the copolymers formed amphiphilic core‐shell aggregates at pH 4.5–7.4 and the particle size was reduced with decreasing pH. In contrast, larger hydrophobic aggregates were formed at pH 4.2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4140–4150, 2008     

Synthesis,complex formation,and dilute‐solution associative behavior of linear poly(methacrylic acid)‐graft‐poly(2‐ethyl‐2‐oxazoline)*

Poly(methacrylic acid) (PMA) and poly(2‐ethyl‐2‐oxazoline) (PEOZO) are a polyacid/polybase pair capable of forming reversible, pH‐responsive, hydrogen‐bonding complexes stabilized by hydrophobic effects in aqueous media. Linear PMA was modified with long‐chain (number‐average molecular weight: 10,000) PEOZO via statistical coupling reactions in organic media to prepare a series of PMA‐graft‐PEOZO copolymers. Potentiometric titrations revealed that the presence of tethered PEOZO markedly increases the pK_a values for PMA‐g‐PEOZO copolymers as compared with simple PMA/PEOZO mixtures at degrees of ionization, α, between 0.0 and 0.1. The dilute‐solution PMA–PEOZO intramolecular association has been probed by monitoring the PEOZO NMR spin–spin (T₂) relaxation as a function of pH. Covalently attached PEOZO side chains participate in complexation at higher values of α than untethered PEOZO. Surprisingly, most PEOZO side chains did not take part in hydrogen bonding at low α, and the highest level of PEOZO incorporation induced a decrease in the number of PMA/PEOZO hydrogen bonds. The polymer self‐diffusion as a function of α was measured with dynamic light scattering. At low pH, the copolymers had no charge and they were in a collapsed form. At high pH, the expected conformational expansion of the PMA units was enhanced at moderate levels of PEOZO incorporation. However, the highest PEOZO incorporation induced the onset of intramolecular associations between PEOZO units along the copolymer chains. Low shear rheometry and light scattering measurements were used in conjunction with the T₂ NMR measurements to propose a model consistent with the aforementioned behavior. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2520–2533, 2004     

Thermoresponsive brush copolymers with poly(propylene oxide‐ran‐ethylene oxide) side chains via metal‐free anionic polymerization “grafting from” technique

Thermoresponsive brush copolymers with poly(propylene oxide‐ran‐ethylene oxide) side chains were synthesized via a “grafting from” technique. Poly(p‐hydroxystyrene) was used as the backbone, and the brush copolymers were prepared by random copolymerization of mixtures of oxyalkylene monomers, using metal‐free anionic ring‐opening polymerization, with the phosphazene base (t‐BuP₄) being the polymerization promoter. By controlling the monomer feed ratios in the graft copolymerization, two samples with the same side‐chain length and different compositions were prepared, both of which possessed high molecular weights and low molecular weight distributions. The results from light scattering and fluorescence spectroscopy indicated that the brush copolymers in their dilute aqueous solutions were near completely solvated at low temperature and underwent slight intramolecular chain contraction/association and much more profound intermolecular aggregation at different stages of the step‐by‐step heating process. Above 50 °C, very turbid solutions, followed by macrophase separation, were observed for both of the samples, which implied that it was difficult for the brush copolymers to form stable nanoscopic aggregates at high temperature. All these observations were attributed, at least partly, to the distribution of the oxyalkylene monomers along the side chains and the overall brush‐like molecular architecture. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2320–2328, 2010     

Novel narrow‐band‐gap conjugated copolymers containing phenothiazine‐arylcyanovinyl units for organic photovoltaic cell applications

A series of novel narrow‐band‐gap copolymers ( P1 ‐ P12 ) composed of alkyl‐substituted fluorene (FO) units and six analogous mono‐ and bis(2‐aryl‐2‐cyanovinyl)‐10‐hexylphenothiazine monomers ( M1 ‐ M6 ) were synthesized by a palladium‐catalyzed Suzuki coupling reaction with two different feed in ratios of FO to M1 ‐ M6 (molar ratio = 3:1 and 1:1). The absorption spectra of polymers P1 ‐ P12 exhibited broad peaks located in the UV and visible regions from 400 to 800 nm with optical band gaps at 1.55–2.10 eV, which fit near the wavelength of the maximum solar photon reflux. Electrochemical experiments displayed that the reversible p‐ and n‐doping processes of copolymers were partially reversible, and the proper HOMO/LUMO levels enabled a high photovoltaic open‐circuit voltage. As blended with [6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) as an electron acceptor in bulk heterojunction photovoltaic devices, narrow‐band‐gap polymers P1 ‐ P12 as electron donors showed significant photovoltaic performance which varied with the intramolecular donor‐acceptor interaction and their mixing ratios to PCBM. Under 100 mW/cm² of AM 1.5 white‐light illumination, the device of copolymer P12 produced the highest preliminary result having an open‐circuit voltage of 0.64 V, a short‐circuit current of 2.70 mA/cm², a fill factor of 0.29, and an energy conversion efficiency of 0.51%. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4285–4304, 2008     

Effect of catalyst systems and reaction conditions on the synthesis of cellulose‐g‐PDMAam copolymers by controlled radical polymerization

Various copper‐based catalyst systems and reaction conditions were studied in the graft copolymerization of N,N‐dimethylacrylamide (DMAam) with a cellulose‐based macroinitiator by controlled radical polymerization. The cellulose macroinitiator with degree of substitution DS = 0.44 was synthesized from dissolving softwood pulp in a LiCl/DMAc solution. The graft copolymerizations of DMAam, using the cellulose macroinitiator and various copper‐based catalyst systems, were then carried out in DMSO solutions. The copolymerization kinetics was followed by ¹H NMR. Water‐soluble cellulose‐g‐PDMAam copolymers were comprehensively characterized by ATR‐FTIR and ¹H NMR spectroscopies and SEC analyses. DLS and steady‐shear viscosity measurements revealed that when the DP_graft of the cellulose‐g‐PDMAam copolymer is high enough, the copolymer forms a more compact structure in water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Stimulus‐responsive polymers based on 2‐hydroxypropyl acrylate prepared by RAFT polymerization

Homopolymerization and diblock copolymerization of 2‐hydroxypropyl acrylate (HPA) has been conducted using reversible addition fragmentation chain transfer (RAFT) chemistry in tert‐butanol at 80 °C. PHPA homopolymers were obtained with high conversions and narrow molecular weight distributions over a wide range of target degrees of polymerization. Like its poly(2‐hydroxyethyl methacrylate) isomer, PHPA homopolymer exhibits inverse temperature solubility in dilute aqueous solution, with cloud points increasing systematically on lowering the mean chain length. The nature of the end groups is shown to significantly affect the cloud point, whereas no effect of concentration was observed over the PHPA concentration range investigated. Various thermoresponsive PHPA‐based diblock copolymers were prepared via one‐pot syntheses in which the second block was either permanently hydrophilic or pH‐responsive. Preliminary studies confirmed that poly(ethylene oxide)‐poly(2‐hydroxypropyl acrylate) (PEO₄₅‐PHPA₄₈) and poly(2‐hydroxypropyl acrylate)‐ poly(2‐hydroxyethyl acrylate) (PHPA₄₉‐PHEA₆₈)diblock copolymers formed well‐defined PHPA‐core micelles in 10 mM sodium nitrate solution at 40 °C and 70 °C with mean hydrodynamic diameters of 20 nm and 35 nm, respectively. In contrast, most other PHPA‐based diblock copolymers investigated formed larger colloidal aggregates in 10 mM NaNO₃ solution at elevated temperatures. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2032–2043, 2010     

Thermosensitive polyalcohols: Synthesis via living cationic polymerization of vinyl ethers with a silyloxy group

Thermosensitive homopolymers and copolymers with hydroxy groups were synthesized via the living cationic polymerization of Si‐containing vinyl ethers. The cationic homopolymerization and copolymerization of five vinyl ethers with silyloxy groups, each with a different spacer length, were examined with a cationogen/Et_1.5AlCl_1.5 initiating system in the presence of an added base. When an appropriate base was added, the living cationic polymerization of Si‐containing monomers became feasible, giving polymers with narrow molecular weight distributions and various block copolymers. Subsequent desilylation gave well‐defined polyalcohols, in both water‐soluble and water‐insoluble forms. One of these polyalcohols, poly(4‐hydroxybutyl vinyl ether), underwent lower‐critical‐solution‐temperature‐type thermally induced phase separation in water at a critical temperature (T_PS) of 42 °C. This phase separation was quite sensitive and reversible on heating and cooling. The phase separation also occurred sensitively with random copolymers of thermosensitive and hydrophilic or hydrophobic units, the T_PS values of which in water could be controlled by the monomer feed ratio. The thermal responsiveness of this polyalcohol unit made it possible to prepare novel thermosensitive block and random copolymers consisting solely of alcohol units. One example prepared in this study was a 20 wt % aqueous solution of a diblock copolymer consisting of thermosensitive poly(4‐hydroxybutyl vinyl ether) and water‐soluble poly(2‐hydroxyethyl vinyl ether) segments, which transformed into a physical gel above 42 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3300–3312, 2003     

Synthesis and photovoltaic properties of copolymers based on bithiophene and bithiazole

Three simple structured D‐A copolymers, PBTBTz‐1 , PBTBTz‐2 , and PBTBTz‐3 , containing bithiophene (BT) donor unit and bithiazole (BTz) acceptor unit with different alkyl chain length were synthesized by the Pd‐catalyzed Stille‐coupling method. The copolymers were characterized by thermogravimetric analysis, UV–vis absorption, electrochemical cyclic voltammetry, and photovoltaic measurements. The results indicate that the introduction of BTz unit to the polythiophene main chain effectively decreases highest occupied molecular orbital levels of the copolymers and increases the open circuit voltage (V_oc) of polymer solar cells (PSCs) based on the copolymers as donor, and the alkyl chain length influences the photovoltaic properties of the polymers significantly. The PSCs based on PBTBTz‐2 and PBTBTz‐3 show higher V_oc up to 0.77 and 0.81 V, respectively. The power conversion efficiency of the PSC based on PBTBTz‐2 :PC₇₀BM = 1:1(w/w) reached 2.58% with short circuit current of 8.70 mA/cm², under the illumination of AM1.5, 100 mW/cm². © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

两亲性树形-线团大单体的合成及其丙烯酸共聚乳液的流变行为

将3,4,5-三(十六烷基氧基)苯甲酰氯先后与分子量为1000的聚乙二醇、甲基丙烯酰氯反应合成了一种新的可聚合两亲性树形-线团大单体——3,4,5-三(十六烷氧基)苯甲酰氧基聚氧乙烯甲基丙烯酸酯(6).通过核磁、红外、元素分析等对产物进行了表征.然后将其与甲基丙烯酸、丙烯酸乙酯进行乳液共聚合,制备了一种疏水树形侧链改性...     

Low‐band gap copolymers containing thienothiadiazole units: Synthesis,optical, and electrochemical properties

Novel low‐band gap alternating copolymers consisting of 9,9‐bis(2‐ethylhexyl)fluorene and 4,6‐di(2‐thienyl)thieno[3,4‐c][1,2,5]thiadiazole and its 3,3″‐dialkyl derivatives were synthesized by Suzuki copolymerization reaction, and their photophysical and electrochemical properties were studied. The copolymers possess small optical band gap 1.3–1.4 eV. The absorption covers the whole visible spectral region. The long‐wavelength absorption maxima in thin films located at approximately 750–785 nm are significantly red shifted compared with those in solution, indicating strong intermolecular interactions. The introduction of alkyl chains to the thiophene units increases the molecular weights of soluble fractions and solubility of the final copolymers, leading to the improved processability of thin films. Polymer solutions exhibited solvatochromism and thermochromism, which is strongly supported by the involvement of the alkyl chains. The copolymers exhibited ambipolar redox properties and reversible electrochromic behavior. The electronic properties are influenced only slightly by alkyl substituents. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2743–2756, 2010     

Synthesis of poly(vinylene arsine)s through the ring‐collapsed radical alternating copolymerization of an organoarsenic homocycle with aliphatic acetylenes and their properties

Poly(vinylene arsine)s with no aromatic substituent ([? CH?CR? AsMe? ]_n) were prepared through a radical alternating copolymerization of acetylenic compounds having an alkyl substituent with an organoarsenic homocycle as an arsenic‐atomic biradical equivalent. The radical reaction between 1‐octyne and pentamethylcyclopentaarsine, with a catalytic amount of 2,2′‐azobisisobutyronitrile without a solvent (60 °C, 10 h), produced the corresponding poly(vinylene arsine)s (45% yield). The copolymers obtained were soluble in tetrahydrofuran, chloroform, hexane, and so on. The copolymers were characterized with ¹H and ¹³C NMR spectra. The number‐average molecular weights of the copolymers were estimated with gel permeation chromatography (chloroform and polystyrene standards) to be 6500. The copolymers showed an emission property attributable to the n–π* transition in the main chain. Irradiation by an incandescent lamp of a mixture of 1‐octyne and 1 also produced poly(vinylene arsine)s. The conversion rate of 1‐octyne during the copolymerization with 2,2′‐azobisisobutyronitrile was measured with gas chromatography analysis and was found to be much slower than that of phenylacetylene. A radical terpolymerization of cyclo‐(AsMe)₅ with 1‐octyne and styrene was carried out to yield the terpolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3604–3611, 2004     

A comparative study of the stimuli‐responsive properties of DMAEA and DMAEMA containing polymers

Reversible addition‐fragmentation chain transfer copolymerization of dimethylaminoethyl acrylate (DMAEA) and methyl acrylate (MA) and their methacrylate counterparts (MMA) has been performed with good control over molecular weight and polydispersity. A screening in composition of copolymers has been performed from 0 to 75% of MA (or MMA). The behavior of these pH and temperature‐sensitive copolymers has been studied in aqueous solution by measuring the cloud point (CP) and the acid dissociation constants (pK_a). The higher incorporation of the hydrophobic monomer in the copolymer resulted in an increase in the pK_a values due to the larger distance between charges thus facilitating the protonation of adjacent nitrogens for both, the acrylate and methacrylate derivatives. The CP behavior of the copolymers has been studied in pure water and the CP values have been found to be irreproducible for the acrylate polymers, as a consequence of the self‐hydrolysis of DMAEA. Hence, kinetic studies have been performed to quantify the degree of self‐hydrolysis at different temperatures and polymer concentrations to explore the full potential and application of these versatile polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3333–3338     

Cinnamate‐functionalized poly(ester‐carbonate): Synthesis and its UV irradiation‐induced photo‐crosslinking

A functionalized cyclic carbonate monomer containing a cinnamate moiety, 5‐methyl‐5‐cinnamoyloxymethyl‐1,3‐dioxan‐2‐one (MC), was prepared for the first time with 1,1,1‐tri(hydroxymethyl) ethane as a starting material. Subsequent polymerization of the new cyclic carbonate and its copolymerization with L ‐lactide (LA) were successfully performed with diethyl zinc (ZnEt₂) as initiator/catalyst. NMR was used for microstructure identification of the obtained monomer and copolymers. Differential scanning calorimetry (DSC) was used to characterize the functionalized poly(ester‐carbonate). The results indicated that the copolymers displayed a single glass transition temperature (T_g) and the T_g decreased with increasing carbonate content and followed the Fox equation, indicative of a random microstructure of the copolymer. The photo‐crosslinking of the cinnamate‐carrying copolymer was also demonstrated. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 161–169, 2009     

Alternatively linking fullerene and conjugated polymers

The stereo‐electronic control over bisadditions of conjugated polymers to fullerene (C₆₀) is explored in the formation of alternating copolymers. The chemistry, resulting configuration, and properties of poly(3‐hexylthiophene)‐alt‐C₆₀ copolymers prepared by either classic pyrrolidine ring formation or an atom transfer radical addition are compared. Both routes result in controlled additions of polymers to C₆₀. Extensive macromolecular modeling through PM6 methods indicate that there is no conjugation between P3HT and C₆₀ in the systems studied. This along with 2D‐NMR, AFM, and photovoltaic characterizations of the materials indicate the importance of the structure of the modified C₆₀ and the nature of the linking group between C₆₀ and P3HT segments in determining the morphology of the copolymers in the solid state. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2304–2317, 2009     

Influence of multiple stimuli on the lower critical solution temperature of new cationic poly(N‐acryloyl‐N′‐ethylpiperazine‐co‐N‐isopropylacrylamide) solutions

New multi‐stimuli responsive cationic copolymers based on N‐acryloyl‐N′‐ethyl piperazine (AcrNEP) and N‐isopropylacrylamide (NIPAM) were prepared by thermal free‐radical solution polymerization in dioxane at 75 °C. The chemical composition of the copolymers was determined by ¹H NMR spectroscopy and was found that the copolymers were slightly rich in NIPAM content than that of AcrNEP. The reactivity of the two monomers for the copolymerization reaction was evaluated by the extended Kelen‐Tüdös method. The distribution of monomer sequence in the copolymer chain was estimated using the terminal copolymerization model. The maximum tendency to alternation (～ 70%) was at 60 mol % of AcrNEP in the monomer feed. The copolymers were readily soluble in water at room temperature at all compositions and exhibited well‐defined lower critical solution temperature (LCST) phenomenon. The influence of various stimuli such as pH, temperature, simple inorganic salts, and surfactants on the LCST of the copolymers was studied in detail. Simple inorganic salts such as sodium chloride, sodium bromide, and sodium sulfate showed a salting‐out effect while sodium iodide showed a salting‐in effect. The salting‐out coefficient of the salts were calculated using the Sestchenow method, and the salting trend followed the order SO₄^2? > Cl^? > Br^? > I^?. The divalent salt was more effective in lowering the LCST than the monovalent salts. The cationic surfactant hexadecyl trimethylammonium bromide at concentrations above the critical micelle concentration caused a gradual increase in the LCST of the copolymer solutions. The intrinsic viscosity and light scattering behavior of the copolymers in water and in sodium chloride solutions were studied in detail. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1175–1183     

Thermal and pH responsive high molecular weight poly(urethane‐amine) with high urethane content

Aliphatic poly(urethane‐amine) (PUA) was synthesized from copolymerization of CO₂ and 2‐methylaziridine (MAZ) using Y(CCl₃COO)₃‐ZnEt₂‐glycerine coordination catalyst, the urethane content of PUA was over 80%, and its yield could reach 90%. PUA with molecular weight as high as 31.0 kg/mol was obtained when the copolymerization reaction was carried out in N,N‐dimethylacetamide (DMAc), mainly due to the good solubility of PUA in DMAc. PUA exhibited reversible thermo‐responsive property in deionized water, and the lower critical solution temperature (LCST) was highly sensitive to its urethane content and molecular weight, which was observed in a broad window from 37 to 90 °C. Furthermore, the phase transition behavior could also be controlled by change of pH value. When the pH value of the PUA aqueous solution changed from 9.2 to 13, the LCST value of the solution decreased from 48.4 °C to 30 °C. Therefore, the PUA showed thermo‐ and pH‐ dual responsive performance in water. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011