End‐group modified poly(methyl vinyl ether): Characterization and LCST demixing behavior in water

A range of hydrophilic poly(methyl vinyl ether) (PMVE) polymers was synthesized by living cationic polymerization of methyl vinyl ether (MVE), having different hydrophilic or hydrophobic chain‐end functionalities. The dissimilar end‐groups were either introduced by end‐capping of the growing polymer chain with LiBH₄, methanol, and water or by functional initiation with 2‐bromo‐(3,3‐diethoxy‐propyl)‐2‐methylpropanoate. The synthesized PMVEs were characterized by ¹H NMR, size exclusion chromatography, and matrix‐assisted laser desorption ionization time of flight, displaying a narrow polydispersity. Modulated temperature DSC was applied to study the influence of the nature of the end‐groups on the solubility behavior of PMVE in water. Terminal‐modification with a hydroxyl function improves the solubility, whereas a Br‐containing end‐group causes the polymer to be insoluble in water at room temperature; however, the special type III lower critical solution temperature demixing behavior being maintained. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 461–469, 2006     

Poly(ether tert‐amine): A novel family of multiresponsive polymer

A novel multiresponsive poly(ether tert‐amine) (PEA) was synthesized by nucleophilic addition/ring‐opening reaction of commercial poly(ethylene oxide) (PEO), poly(propylene oxide) (PPO), and di‐epoxy and di‐amine monomer. The process of synthesis was very simple and green in ethanol as reactive media. These PEAs exhibit sharp response to temperature, pH, and ionic strength, with adjustable and sharp phase transitions in the range of 27–100 °C. The lower critical solution temperature (LCST) of PEA's aqueous solution presents a linear relationship to the PEO content (y = 35.7 + x), indicating well‐tunable LCST. The concentration of PEA has no obvious effect on LCST. Therefore, PEA will be potential in applications of drug delivery, separation, and biotechnology. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1292–1297, 2009     

Molecular Dynamics Investigation of the Thermo‐Responsive Polymer Poly(N‐isopropylacrylamide)

Using molecular dynamics simulations with an OPLS force field, the lower critical solution temperature (LCST) of single‐ and multiple‐chain PNIPAM solutions in water is investigated. The sample containing ten polymer chains shows a sudden drop in size and volume at 305 K. Such an effect is absent in the single‐chain system. Large fluctuations of the physical properties of a short single‐chain prevent any clear detection of the LCST for the chosen model system, at least on the time scale of 200 ns. The results provide evidence that a critical number of PNIPAM monomer units must be present in the simulated system before MD simulations are capable to detect conformational changes unambiguously.

     

Thermo‐ and pH‐Responsive Micelles of Poly(acrylic acid)‐block‐Poly(N,N‐diethylacrylamide)

Summary: The bis‐hydrophilic block copolymer, poly(acrylic acid)₄₅‐block‐poly(N,N‐diethylacrylamide)₃₆₀, was obtained after hydrolysis of poly(tert‐butyl acrylate)₄₅‐block‐poly(N,N‐diethylacrylamide)₃₆₀, synthesized by sequential anionic polymerization of tert‐butyl acrylate (tBA) and N,N‐diethylacrylamide (DEAAm) in the presence of Et₃Al. The polymer is stimuli‐sensitive with respect to both pH and temperature in aqueous solution, reversibly forming spherical crew‐cut micelles with PDEAAm‐core (〈R_h〉_z = 21.5 nm) under alkaline conditions for T > 35 °C as well as inverse star‐like micelles with an expanded PAA‐core (〈R_h〉_z = 43.8 nm) under acidic conditions for T < 35 °C, as indicated by dynamic light scattering.

Modes of micelle formation for poly(acrylic acid)₄₅‐block‐poly(N,N‐diethylacrylamide)₃₆₀ in aqueous solution depending on the pH and temperature.     

Aqueous solution behavior of comb‐shaped poly(2‐ethyl‐2‐oxazoline)

A series of comb polymers consisting of a methacrylate backbone and poly(2‐ethyl‐2‐oxazoline) (PEtOx) side chains was synthesized by a combination of cationic ring‐opening polymerization and reversible addition–fragmentation chain transfer polymerization. Small‐angle neutron scattering (SANS) studies revealed a transition from an ellipsoidal to a cylindrical conformation in D₂O around a backbone degree of polymerization of 30. Comb‐shaped PEtOx has lowered T_g values but a similar elution behavior in liquid chromatography under critical conditions in comparison to its linear analog was observed. The lower critical solution temperature behavior of the polymers was investigated by turbidimetry, dynamic light scattering, transmission electron microscopy, and SANS revealing decreasing T_cp in aqueous solution with increasing molar mass, the presence of very few aggregated structures below T_cp, a contraction of the macromolecules at temperatures 5 °C above T_cp but no severe conformational change of the cylindrical structure. In addition, the phase diagram including cloud point and coexistence curve was developed showing an LCST of 75 °C of the binary mixture poly[oligo(2‐ethyl‐2‐oxazoline)methacrylate]/water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Photomechanical Switching Behavior of Semi‐Interpenetrating Polymer Network Consisting of Azobenzene‐Carrying Crosslinked Poly(vinyl ether) and Polycarbonate

Summary: A novel semi‐interpenetrating polymer network (semi‐IPN) with photomechanical switching ability was developed by a cationic copolymerization of azobenzene‐containing vinyl ethers in a matrix of a linear polycarbonate (PC). The semi‐IPN film showed reversible deformation upon switching the UV irradiation on and off and responded with unprecedented rapidity. The photomechanical effect is attributed to a reversible change between the highly aggregated and dissociated states of the azobenzene groups.

The reversible UV response of the length of the semi‐IPN film at 25 °C.     

N+离子注入聚对苯乙炔衍生物的非线性光学性能

以对甲氧基苯酚和溴代异戊烷为原料,用脱氯化氢反应制备可溶性聚[2-甲氧基-5-(3'-甲基)丁氧基]对苯乙炔(MMB-PPV),通过核磁氢谱(1HNMR)和红外光谱(FTIR)对产物分子的结构进行表征.用能量为15keV、剂量为3.8×1015～9.6×1016ions/cm2的氮正离子(N+)对MMB-PPV薄膜进行注入改性.紫外-可见吸收光谱(UV-Vis)显示,注入离子在MMB-PPV薄膜内部引入杂质能级,破坏了分子的共轭结构.随着注入剂量增加,吸收边逐渐向长波方向移动,且分子激发态和基态间的光学带隙由2.12eV减小至1.81eV.用简并四波混频(DFWM)技术研究了离子注入MMB-PPV薄膜的三阶非线性光学性能.结果表明,未注入薄膜的三阶非线性极化率(χ(3))值为7.1×10-10esu,随着注入剂量的增加,χ(3)值逐渐增大,当注入剂量达到3.8×1016ions/cm2时,χ(3)值提高到9.3×10-9esu,继续增加注入剂量,χ(3)值开始下降,当注入剂量为9.6×1016ions/cm2时,χ(3)值降低到1.5×10-10esu.对离子注入MMB-PPV薄膜χ(3)值变化的机理进行了探讨.     

Application of Ultrasonic Attenuation Measurements in the Studies on Macromolecular Conformational Behaviors

——Phase Behavior of the Aqueous Solution of Poly(vinyl methyl ether) Sensitive to Temperature and the Modification of the Behavior by Using Poly(acrylic acid) The phase behavior of the aqueous solution of poly(vinyl methyl ether) (PVME) sensitive to temperature and the modification of the behavior by using poly(acrylic acid) (PAA) have been studied by ultrasonic attenuation measurements and fluorescence probe techniques. It has been observed that PVME solution is transparent at room temperature and becomes turbid upon heating. The solution turns clear again as soon as the temperature is decreased to room temperature. The heating and cooling process can be repeated for many times. The phase behavior of the solution sensitive to temperature is attributed to the conformational changes of the polymer. PVME may adopt an open coil conformation at room temperature. With this conformation, the polymer is well miscible with the solvent, water, and thereby the system is a real solution. The polymer may adopt a compact coil conformation when the temperature is higher than a specific value, which is called the LCST (the lower critical solution temperature) of PVME. In this case, the polymer tangles to each other and forms various aggregates, which can scatter incident light and ultrasonic waves greatly, resulting in the phase separation. Introduction of PAA decreases the temperature sensitivity of the phase behavior of the polymer. The nature of the inhibition is attributed to the complexation of PAA with PVME and the strong hydrophilicity of PAA. Results from fluorescence probe studies are in accordance with those from ultrasonic attenuation measurements, indicating again that the ultrasonic attenuation method can be successfully used for the qualitative studies of polymer conformations and complexation between polymers.     

The Association of Tetraalkylammonium Ions with Poly(vinyl methyl ether) in Water and its Effect on Phase‐Separation Behavior as Studied by Micro‐Raman Spectroscopy

Summary: The thermosensitive phase‐separation of poly(vinyl methyl ether) in water has been investigated by micro‐Raman spectroscopy in the presence of tetraalkylammonium bromides. The equilibrium distribution of both polymer and salts to the polymer‐rich and solvent‐rich phases was determined as a function of temperature. Tetraalkylammonium ions with longer alkyl chains associate more strongly with PVME and raise the phase‐transition temperature due to an increase in hydrophilicity.

     

聚甲基丙烯酸甲酯与聚醋酸乙烯酯共混的红外光谱研究

用红外光谱(FTIR)研究了聚甲基丙烯酸甲酯(PMMA)与聚醋酸乙烯酯(PVAc)共混体系相容性,在160℃以上共混体系发生相分离;分相体系与非分相体系的FTIR谱明显不同;共混体系的FTIR谱不能从两统组分红外光谱简单加和得到;结果表明大分子构象发生了变化,PMMA/PVAc体系相容可能是大分子构象熵变所致。     

Poly(methyl vinyl ether‐alt‐maleic acid)‐Functionalized Porous Silicon Nanoparticles for Enhanced Stability and Cellular Internalization

Currently, developing a stable nanocarrier with high cellular internalization and low toxicity is a key bottleneck in nanomedicine. Here, we have developed a successful method to covalently conjugate poly(methyl vinyl ether‐co‐maleic acid) (PMVE‐MA) copolymer on the surface of (3‐aminopropyl)triethoxysilane‐functionalized thermally carbonized porous silicon nanoparticles (APSTCPSi NPs), forming a surface negatively charged nanovehicle with unique properties. This polymer conjugated NPs could modify surface smoothness, charge, and hydrophilicity of the developed NPs, leading to considerable improvement in the colloidal and plasma stabilities via enhanced suspensibility and charge repulsion. Furthermore, despite the surface negative charge of the polymer‐conjugated NPs, the cellular internalization was increased in both MDA‐MB‐231 and MCF‐7 breast cancer cells. These results provide a proof‐of‐concept evidence that such polymer‐based PSi nanocomposite can be extensively used as a promising candidate for intracellular drug delivery.

     

Sustained Drug Release by Thermoresponsive Sol–Gel Hybrid Hydrogels of Poly(N‐Isopropylacrylamide‐co‐3‐(Trimethoxysilyl)Propyl Methacrylate) Copolymers

Poly(N‐isopropylacrylamide‐co‐3‐(trimethoxysilyl)propyl methacrylate), P(NIPAAm‐co‐TMSPMA), copolymers with relatively high TMSPMA contents without insoluble fraction are successfully synthesized. Subsequent sol–gel reactions in both the absence and presence of tetraethyl orthosilicate lead to gels with high gel fractions. The resulting gels undergo gel collapse at 28.6–28.7 °C, i.e., below that of poly(N‐isopropylacrylamide) homopolymer of 34.3 °C. Unexpectedly, the theophylline‐loaded hybrid gels release the drug not only below but also above the gel collapse temperature (GCT) with considerable rates and released amounts of drug. Surprisingly, evaluation of the sustained release profiles by the Korsmeyer–Peppas equation indicates that the release occurs by Fickian diffusion above GCT, which can be attributed to the lack of significant drug–polymer interaction at such temperatures. These results can be widely applied for the design and utilization of TMSPMA‐based sol–gel polymer hybrids with desired release profiles of solutes below and above GCT for a variety of applications.

     

Preparation of Polymer Nanofibers Containing Silver Nanoparticles by Using Poly(N‐vinylpyrrolidone)

Summary: Poly(N‐vinylpyrrolidone) (PVP) was used in two methods to prepare polymer nanofibers containing Ag nanoparticles. The first method involved electrospinning the PVP nanofibers containing Ag nanoparticles directly from the PVP solutions containing the Ag nanoparticles. N,N‐Dimethylformamide was used as a solvent for the PVP as well as a reducing agent for the Ag⁺ ions in the PVP solutions. In the second method, poly(vinyl alcohol) (PVA) aqueous solutions were electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles. The Ag nanoparticles were evenly distributed in the PVA nanofibers. PVP containing Ag nanoparticles could be used to introduce Ag nanoparticles to other polymer nanofibers that are miscible with PVP.

TEM image of a PVA nanofiber electrospun with 5 wt.‐% of the PVP containing Ag nanoparticles.     

Thermal diffusivity study of polystyrene/poly(vinyl methyl ether) blends by flash radiometry

This article presents thermal diffusivity (D) measurements by flash radiometry for the polymer blend of polystyrene (PS) and poly(vinyl methyl ether) (PVME) with lower critical solution temperature (LCST) phase diagram. Dependence of D on PS content measured at 100°C coincides a phase diagram determined by a cloud point measurement. D value for the blend decreases with increasing PS content and has minimum value at the PS content around 20 wt % from which D increases again with increasing PS content. If the concentration fluctuation between two components in the miscible states at the temperature close to LCST causes the remarkable phonon scattering, the composition dependence of D would resemble the phase diagram. D for the sample in the phase-separated state is larger than that for the miscible state. The larger D in the phase-separated sample would be due to the decrease of the total surface area microscopically contacted to the counter component in the phase-separated state. Dependence of D on temperature for the phase-separated sample is quite different from that of the miscible one. On an isothermal measurement of D for PS/PVME (10 : 90) at 110°C just below the cloud point, D started to increase at time above 100 min and leveled out above 250 min. Isothermal observation of sample film by a differential interference contrast microscopy showed the creation of some structure due to the nucleation and growth of interface at 225 min and it became obvious above 250 min. Thus, the increase in D at 110°C implies that D can sensitively reflect the change in microscopic structures which follows the nucleation and growth of interface. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1869–1876, 1997     

Molecularly Imprinted Polymer for Solid‐Phase Extraction of Ecteinascidin 743 from Sea Squirt

Ecteinascidin 743 from sea squirt is one of the most original anti‐tumoral activity compounds, as proven by the Natural Cancer Institute. Ecteinascidin 743 could be obtained with traditional liquid extraction, but it should be purified and separated from the extract. A molecularly imprinted solid‐phase extraction procedure was developed for the selective separation. Ecteinascidin 743 was used as the template and the polymer was synthesized in a methanol environment. Water and n‐hexane as the washing solvents can eliminate most of the interference. Good linearity and low relative standard deviations (less than 4.39%) justify its continuing development.     

Novel Polymer Electrolyte Membrane,Based on Pyridine Containing Poly(ether sulfone), for Application in High‐Temperature Fuel Cells

Summary: Novel poly(aryl ether sulfone) copolymers containing 2,5‐biphenylpyridine and tetramethyl biphenyl moieties were synthesized by polycondensation of 4‐fluorophenyl sulfone with 2,5‐(4′,4″ dihydroxy biphenyl)pyridine and tetramethyl biphenyl diol. Copolymers with different molecular weights and different monomer compositions were obtained. These copolymers exhibit excellent film‐forming properties, mechanical integrity, and high modulus up to 250 °C, high glass transition temperatures (above 280 °C) as well as high thermal stability up to 400 °C. In addition to the above properties required for PEMFC application, this novel material shows high oxidative stability and acid doping ability, enabling proton conductivity in the range of 10⁻² S · cm⁻¹ above 130 °C.

Synthesis of copolymers with high acid uptake and ionic conductivity.     

Heat capacity of poly(vinyl methyl ether)

The heat capacity of poly(vinyl methyl ether) (PVME) has been measured using adiabatic calorimetry and temperature‐modulated differential scanning calorimetry (TMDSC). The heat capacity of the solid and liquid states of amorphous PVME is reported from 5 to 360 K. The amorphous PVME has a glass transition at 248 K (?25 °C). Below the glass transition, the low‐temperature, experimental heat capacity of solid PVME is linked to the vibrational molecular motion. It can be approximated by a group vibration spectrum and a skeletal vibration spectrum. The skeletal vibrations were described by a general Tarasov equation with three Debye temperatures Θ₁ = 647 K, Θ₂ = Θ₃ = 70 K, and nine skeletal modes. The calculated and experimental heat capacities agree to better than ±1.8% in the temperature range from 5 to 200 K. The experimental heat capacity of the liquid rubbery state of PVME is represented by C_p(liquid) = 72.36 + 0.136 T in J K^?1 mol^?1 and compared to estimated results from contributions of the same constituent groups of other polymers using the Advanced Thermal AnalysiS (ATHAS) Data Bank. The calculated solid and liquid heat capacities serve as baselines for the quantitative thermal analysis of amorphous PVME with different thermal histories. Also, knowing C_p of the solid and liquid, the integral thermodynamic functions of enthalpy, entropy, and free enthalpy of glassy and amorphous PVME are calculated with help of estimated parameters for the crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2141–2153, 2005     

Temperature-sensitive poly(vinyl methyl ether) hydrogel beads

Temperature-sensitive hydrogel beads were prepared by radiation crosslinking of poly(vinyl methyl ether) PVME spheres wrapped in Ca-alginate. The obtained gel beads have diameters in the sub-millimeter or millimeter range (depending on the PVME concentration). They were characterized by sol-gel analysis, swelling measurements, and differential scanning calorimetry. The gel content g increases with increasing radiation dose D. The swelling degree Q_v decreases with increasing PVME concentration c_p and increasing D. In comparison to PVME bulkgels the phase-transition temperature of the synthesized PVME gel beads is a little decreased.     

Stimuli‐responsive brush‐shaped conjugated polymers with pendant well‐defined poly(vinyl ether)s

For the synthesis of brush‐shaped conjugated polymers consisting of a poly(phenylene butadiynylene) backbone and well‐defined poly(vinyl ether) (polyVE) side chains, we designed polyVE‐based macromonomers bearing a diethynyl benzene group at the terminus and applied them to the grafting through synthesis. The macromonomer (DE‐PIBVE) was synthesized by living cationic polymerization of isobutyl VE (IBVE) using a functionalized initiator (TMS‐DEVE‐TFA) having a TMS protected diethynyl benzene moiety, followed by deprotection of the TMS groups. As a result, we succeeded in the synthesis of the target brush‐shaped conjugated polymers [poly(DE‐PIBVE)] by oxidative coupling reaction of the diethynyl benzene groups. We found that the solution of poly(DE‐PIBVE) with a specific side chain length exhibited solvatochromism and thermochromism depending on the polarity of the media employed. This phenomenon was attributed to self‐assembly in polar media due to the intermolecular π–π interaction between neighboring conjugated polymer backbones, where the self‐assembly behavior would be closely related to the pendant polyVE structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3318–3325     

Access to Poly{N‐[3‐(dimethylamino)propyl](meth)acrylamide} via Microwave‐Assisted Synthesis and Control of LCST‐Behavior in Water

In the present paper, the microwave (MW)‐assisted synthesis of the alkaline N‐[3‐(dimethylamino)propyl]methacrylamide ( 4 ) and ‐acrylamide ( 5 ) monomers within minutes is described. The reaction was carried out by mixing and subsequent irradiation of 3‐dimethylamino‐1‐propylamine ( 3 ) and (meth)acrylic acid ( 1 / 2 ) without addition of solvent. After polymerization, the obtained homopolymers ( 6 / 7 ) exhibit lower critical solution temperature (LCST) behavior in water at 35 °C only at pH = 14. The LCST‐behavior can be influenced by N‐oxidation of the tertiary amino group with hydrogen peroxide or by formation of a polymer‐inclusion complex ( 6a ) of 6 and β‐cyclodextrin (β‐CD) by addition of randomly‐methylated β‐CD.