Quenching of pyrene fluorescence as a technique for characterisation of swelling of interpenetrating polymer network: polyethylene/poly(styrene-co-butylmethacrylate)

A real-time monitoring of oxygen quenching of monomer fluorescence of bound probes: 1-pyrenemethyl methacrylate (PyMMA) and 1-pyrenemethyl(4-vinylbenzyl)ether (4-(1-pyrenyl)methoxymethylstyrene, PyMMS) was used for study of swelling of interpenetrating polymer network (IPN) consisting of polyethylene/poly(styrene-co-butylmethacrylate) (PE/P(S-co-BMA)) with different network density. The curves of oxygen quenching of pyrene chromophore were fitted to the monoexponential form of second Fick Law. The estimated diffusion coefficient of oxygen was in the range of 1-10 × 10⁻⁶ cm² s⁻¹ depending on the solvent and phase of IPN system. There is no dependence of fluorescence quenching by oxygen on cross-link density in this IPN systems.     

Pyrene Fluorescence in the Presence of Acrylic Acid-Ethyl Methacrylate Copolymers: Effect of the Copolymer Composition in the Formation of Microdomains*

The properties of aqueous solutions of acrylic acid-ethyl methacrylate (EMA) copolymers have been investigated using pyrene and pyrene pyrenebutyltrimethylammonium (PBTA) as probes. Static and dynamic fluorescence have been used to obtain information about the microenviron-ments formed. Micropolarity studies using the I₁/I₃ ratio of the vibronic bands of pyrene show the formation of hydrophobic domains. At low pH the increase of the amount of ethyl methacrylate in the copolymers shows that aqueous microdomains are excluded from the core of the polymer, for the copolymers with high content of EMA low polarity microdomains are still present on the mac-romolecular chain even at higher pH. The pH-induced conformational transition indicates that the more hydro-phobic copolymers adopt a more tightly coiled conformation. Compared to PAA, the decay times for both probes are increased twice for the polymer with 25% molar proportion of EMA. The fluorescence quenching of the probes by nitromethane depends on pH, copolymer composition and probe structure. The efficiency of quenching decreases with increase of the EMA proportion in the copolymers. Pyrene is more efficiently quenched than PBTA as a consequence of the latter being located in more internal (less accessible) sites of the polymer structure.     

利用聚合物自组装实现绿色荧光蛋白生色团的荧光增强

根据绿色荧光蛋白的发光原理,采用聚乙二醇与聚甲基丙烯酸甲酯的两亲性两嵌段聚合物通过自组装包覆生色团的方式,模拟了绿色荧光蛋白发光,考察了组装行为对光学性能的影响,并将其用于细胞成像.通过核磁共振、高分辨质谱、傅里叶变换红外光谱、凝胶渗透色谱、紫外-可见吸收光谱及荧光光谱等表征了生色团分子和聚合物的结构及性能.生色团紫外最大吸收在371 nm,荧光最大发射峰在428 nm.聚合物和生色团进行组装后,其紫外吸收消失,而最大荧光发射峰强度大大增强,且发生了约70 nm的红移,这是因为组装使得生色团的自由旋转受到了限制,且生色团共平面性增加.动态光散射(DLS)和透射电镜(TEM)证明了纳米粒子的结构和尺寸.由于尺寸适合且具有较好的荧光性能,纳米粒子成功应用于细胞成像.这种绿色荧光蛋白生色团的简单自组装方式在生物成像领域具有良好应用前景.     

Preparation of highly monodisperse fluorescent polymer particles by miniemulsion polymerization of styrene with a polymerizable surfactant

Miniemulsion polymerization of styrene (St) in the presence of a hydrophobe (hexadecane:HD) using a cationic polymerizable surfactant (N,N-dimethyl-N-n-dodecyl-N-2-methacryloyloxyethylammonium bromide:C(12)Br) and a cationic initiator (2,2'-azobis(2-amidinopropane) dihydrochloride:V50), called St/C(12)Br/V50 hereafter, proceeded efficiently compared with that using sodium dodecyl sulfate (SDS) and potassium persulfate (KPS), i.e., St/SDS/KPS, providing monodisperse polystyrene latex particles with a narrower particle size distribution. In St/C(12)Br/AIBN, where an oil-soluble initiator, i.e., 2,2'-azobisisobutyronitrile (AIBN), was used in place of V50, little changes in polymerization kinetics or in particle size distribution were observed, while a significant drop in polymerization rate and a broad particle size distribution were observed with St/SDS/AIBN. A polymerizable pyrene derivative (1-pyrenylmethyl methacrylate: PyMMA) was quantitatively incorporated into monodisperse latex particles in St/PyMMA/C(12)Br/V50 compared to pyrene (Py) in St/Py/C(12)Br/V50. Contrary to our expectation, however, increased excimer emission was observed with St/PyMMA/C(12)Br/V50 particles, indicating less evenly distributed pyrene chromophores in the particles. The fluorescence lifetime of pyrene chromophores in St/Py/C(12)Br/V50 particles was determined to be 286 ns, which was 17 times longer than that of pyrene in THF solution.     

Synthesis of highly dispersed,block copolymer‐grafted TiO2 nanoparticles within neat block copolymer films

The objective of the study is to formulate exclusive block copolymer (BCP) nanocomposites by dispersing bcp end‐grafted nanoparticles (bcp‐g‐nps) of PMMA‐b‐PS‐g‐TiO₂ within PS‐b‐PMMA matrix. PMMA‐b‐PS‐g‐TiO₂ is synthesized using a “grafting‐to” approach and characterized by XPS and TGA to establish that the copolymer chains were bonded to NPs. Good dispersion of bcp‐g‐nps in PMMA and PS‐PMMA bcp films is observed, in contrast to poor dispersion in PS films. In PS‐PMMA films, the compatible and identical bcp nature of the end‐grafted polymer, and large NP size caused it to span across entire PS‐PMMA domains. Poor and good dispersion in PS and PMMA matrices, respectively, can be rationalized by the fact that NPs interactions are driven by the PMMA at the outer corona of the bcp‐g‐nps. Developing bcp‐g‐nps as a strategic route to preparation of highly dispersed high permittivity NPs like titanium dioxide (TiO₂) in bcp matrix can have important ramifications for energy storage devices. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 468–478     

Structure and properties of polystyrene-polyethylene interpenetrating polymer network (ipn)-like systems

A series of samples of polystyrene (PS) –polyethylene (PE) interpenetrating polymer network (IPN)–like system was prepared by synthesis in situ. The measurement of uniaxial compression modulus of the IPN samples was used for the determination of mean molar mass of the polymer chain between two junction points of the polymer network – M̌_C. The electron microscopic records gave an evidence about two phase structure of the IPN samples. Generally, the crystalline part of PE network in all IPN investigated samples is relatively low. The influence of the concentration of crosslinking agent on mechanical behaviour of the IPN samples was studied.     

NONLINEAR OPTICAL PROPERTIES OF A-SHAPED NITROPYRIMIDINE DERIVATIVES AND ITS POLYMERIC FILMS

Three A-shaped nitropyrimidine derivatives with benzyl or furfuryl as bridge havebeen synthesized. They possess shorter absorption wavelengths (λ_(cut-off))<400 nm) andhigher βμ values (around 10~(-46) esu). The second order nonlinear optical coefficient d_(33) ofpoled BNPMOPMDA/PMMA doped film is 1.2-2.0×10~(-9) esu obtained by in-situ SHGmeasurements. It can be expected that the chromophore-functionalized polymer containinghigher number density of synthesized chromophore as side chain will be the potential blue-light transparent frequency doubling materials.     

Synthesis and characterization of polyaniline filled PU/PMMA interpenetrating polymer networks

A series of conducting interpenetrating polymer networks (IPNs), are prepared by sequential polymerization of castor oil based polyurethane (PU) with poly(methyl methacrylate) (PMMA) and polyaniline doped with camphor sulphonic acid (PAni)_CSA. The effect of different amount of PAni (varies from 2.5-12.5%) on the properties of PU/PMMA (50/50) IPNs such as electrical properties like conductivity, dielectric constant and dissipation factor; mechanical properties like tensile strength and percentage elongation at break have been reported. (PAni)_CSA filled IPNs shows improved tensile strength than the unfilled IPN system. The thermal stability and surface morphology of unfilled and (PAni)_CSA filled PU/PMMA (50/50) IPN sheets were investigated using a thermogravimetric analyzer (TGA) and a scanning electron microscope (SEM). TGA thermograms of (PAni)_CSA filled PU/PMMA (50/50) IPNs show a three-step thermal degradation process. SEM micrograms of filled PU/PMMA IPN system shows spherulitic structure at higher concentration of (PAni)_CSA.     

PEGDA‐based luminescent polymers prepared by frontal polymerization

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1‐pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT‐IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene‐containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA‐co‐PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2890–2897     

模仿绿色荧光蛋白的荧光聚合物的合成和光学性质研究

受绿色荧光蛋白(GFP)荧光增强原理启发,采用开环聚合制备了两亲性聚乙二醇-生色团-聚己内酯(PEG-c-PCL)嵌段聚合物.通过核磁共振氢谱和碳谱(1H-,13C-NMR)、傅立叶变换红外光谱(FTIR)、凝胶渗透色谱(GPC)和紫外可见吸收光谱(UV-Vis)等证明其结构和性质.生色团和聚合物有相似的紫外吸收光谱,且最大吸收峰都在371 nm.荧光发射光谱表明,生色团的发射峰在427 nm,但聚合物的荧光发射峰出现了6 nm的红移,这是高分子化引起的结果.透射电镜(TEM)和动态光散射(DLS)证明了该两亲性嵌段聚合物能够组装成为纳米粒子.当聚合物组装成纳米粒子后,荧光强度增大了55倍,并且荧光发射峰出现了14 nm的红移,这些现象可归结于荧光生色团自由旋转的限制和组装导致的相互作用增强.     

The effect of γ‐cyclodextrin addition in the self‐assembly behavior of pyrene labeled poly(acrylic) acid with different chain sizes

The interaction between poly(acrylic acid) polymers (PAA) of low‐ (2000 g/mol) and high‐ (450,000 g/mol) molecular weight (M_w) hydrophobically modified with pyrene (PAAMePy) and β‐ and γ‐cyclodextrins (β‐CD, γ‐CD) was investigated with fluorescent techniques. The interaction with β‐CD promotes little variation in the spectral and photophysical behavior of the polymer, whereas significant changes are observed upon addition of γ‐CD. The degree of inclusion (between the pyrene groups of the polymer and the cyclodextrins) is followed through the observation of the changes in the absorption, excitation (collected in the monomer and excimer emission regions) and emission (I_E/I_M ratio) spectra and from time‐resolved data. Within the studied range of γ‐CD concentration, the fluorescence decays of the long chain (high M_w) PAAMePy polymers were found tri‐exponential in the monomer and excimer emission regions in agreement with previous studies. In the case of the low M_w PAAMePy polymers, tri‐exponential decays were observed at the monomer and excimer emission wavelengths. However, when a γ‐CD concentration of 0.01 and 0.03 M is reached for, respectively, the low‐ and high‐labeled pyrene short chain (low M_w) polymers, the fluorescence decays in the excimer region become biexponential (two excimers) with no rising component, thus showing that all pyrene groups are encapsulated (and preassociated) into the γ‐CD cavity. In the case of the high M_w polymers, the addition of γ‐CD has been found to change the level of polymer interaction from pure intramolecular (water in the absence of cyclodextrin) to a coexistence of intra‐ with intermolecular interactions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1402–1415, 2008     

Two-component interpenetrating polymer networks (IPNs) from polyurethanes and epoxies. I. Studies on full IPN,pseudo-IPN,and graft polymer alloys of polyurethanes and epoxies

In this article we review the synthesis and morphology and the physical and mechanical properties of two-component interpenetrating polymer networks (IPNs) from polyurethane and epoxy polymers; the corresponding pseudo-IPNs and grafted IPNs are also discussed. A comparison was made of full IPNs, pseudo-IPNs, grafted IPNs, and related homopolymers by examining their mechanical properties, mechanical spectra, and electron microscopy on an investigation of the effects of interpenetration or permanent entanglement in the IPN and related systems. This interpenetration has resulted in improved compatibility between the two polymer systems and has caused a decrease in the degree of phase separation. An observed shift in the dynamic glass transition temperatures (T_gs) of the two components which yielded a single IPN T_g further substantiates our results.     

Particle monolayer formation at the air–water interface by silica particle with well‐defined grafted polymer

Particle monolayer formation at the air–water interface by polymer‐grafted colloidal silica was investigated. Methyl methacrylate (MMA) was polymerized from initiative bromide groups at colloidal silica surface by atom transfer radical polymerization. We obtained polymer‐grafted silica particle (SiO₂‐PMMA) with relative narrow polydispersity of PMMA. For the polymer‐grafted particle with high graft density, particle monolayer formation was confirmed by π‐A isotherm measurement and SEM observation. Interparticle distance was controllable by surface pressure. Furthermore, grafted polymer chains were suggested to be fairly extended at the air–water interface. However, for the polymer‐grafted particle with low graft density, monolayer structure on substrate showed aggregation and voids. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2789–2797, 2006     

四(4,4',4'',4'''-N,N-二氨基)四苯乙烯光致发光与分子的构象效应

利用还原偶联方法合成出新化合物四(4,4',4',4''-N,N-二氨基)四苯乙烯（ TDETE）。通过测定该化合物在溶液、掺杂聚合物中及晶体粉末的稳态-瞬态荧光光 谱、荧光量子产率和辐射衰变速率常数等。讨论了分子的构象效应等因素对TDETE 光致发光行为的影响。在一定浓度下TDETE溶液存在着三个发光带,分别为全扭曲 构象分子（位于345nm附近的发光I带）、半扭曲构象分子（位于430nm附近的发光 II带）和激基缔合物（530发光III带）的辐射衰变所致。在聚合物（PMMA）中,一 方面由于分子单键的自由旋转扭曲受到遏制,表现为II带的辐射衰变速率常数(kf 值)增大、同时非辐射衰变速率常数knf值减小;另一方面,TDETE分子之间相互作 用得到加强而有利一缔合物形成,结果,使发光II带和III带合二为一出现强而宽 的发射峰,荧光量子产率从溶液中的0.055提高到0.855。此外,在PMM介制裁中观 测到TDETE分子聚集体在626nm处的发光带（IV）,数粉末态中聚集体IV带的强度骤 增,峰值波长红移至650nm。     

Synthesis of versatile poly(PMMA‐b‐VI) macromonomer‐based hydrogels via infrared laser ignited frontal polymerization

In this work, poly((PMMA‐b‐VI)‐co‐AA) (MMA = methyl methacrylate; VI = 1‐vinylimidazole; AA = acrylic acid) hydrogels and poly((PMMA‐b‐VI)‐co‐AA)/TPU (TPU = thermoplastic polyurethane) IPN (interpenetrating polymer networks) hydrogels have been fabricated via versatile infrared laser ignited frontal polymerization by using poly(PMMA‐b‐VI) macromonomer as the mononer. The frontal velocity and T_max (the highest temperature that the laser beam detected at a fixed point) can be adjusted by varying monomer weight ratios, the concentration of BPO (BPO = benzoyl peroxide) and the amount of TPU. Moreover, the addition of TPU enhances the reactant viscosity to suppress the “fingering” of frontal polymerization (FP) and decrease T_max of the reaction, providing a new inert carrier (TPU) to assist FP. Through the characterization of Fourier transform‐infrared spectroscopy (FT‐IR), scanning electron microscope (SEM), and differential scanning calorimetry (DSC), the desired structure can be proved to exist in the IPN hydrogels. Furthermore, poly((PMMA‐b‐VI)‐co‐AA)/TPU IPN hydrogels possesses more excellent mechanical behaviors than hydrogels without IPN structure. Besides, the poly((PMMA‐b‐VI)‐co‐AA) hydrogels present splendid sensitive properties toward substances of different flavor including sourness (CA, citric acid or GA, gluconic acid), umami (SG, sodium glutamate), saltiness (SC, sodium chloride), sweetness (GLU, glucose), enabling their potential as artificial tongue‐like sensing materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1210–1221     

Fluorescence Probe Study of the Interaction Between Acrylic Acid-co-Ethyl Methacrylate Copolymers and Sodium Dodecylsulfate

The interaction between sodium dodecylsulfate (SDS) and acrylic acid (AA)–ethyl methacrylate (EMA) copolymers has been investigated using steady state fluorescence and conductimetric measurements to assess the effect of the polymer composition on the aggregation process. Micropolarity studies using the ratio between the emission intensities of the vibronic bands of pyrene (I₁/I₃) and the shift of the fluorescence emission of pyrene-3-carboxaldehyde show that the interaction of SDS with AA-EMA copolymers occurs at surfactant concentrations smaller than that observed for the pure surfactant in water and depends on the copolymer composition. The increase of ethyl methacrylate in the copolymers lowers the critical aggregation concentration (CAC) due to the larger hydrophobic character of the polymer backbone. The formation of aggregates on the macromolecule is induced mainly by hydrophobic interactions, but the process is also influenced by the ionic strength due to the counter-ions of the polyelectrolyte.     

Aggregation behavior of novel hyaluronan derivatives—a fluorescence probe study

Aggregation properties of hydrophobized hyaluronan with different molecular weights and degrees of substitution were studied using pyrene and perylene as fluorescence probes. Both probes in contrast to native biopolymer confirmed aggregation of modified hyaluronan. The critical aggregation concentration (cac) was determined by the pyrene I₁/I₃ and perylene fluorescence intensity method. The cac value varied both with the molecular weight and the degree of substitution and was between 0.610 and 0.003 g·L^?1. Pyrene polarity scale confirmed formation of hydrophobic domains.     

Study of maleated ethylene-propylene copolymers by fluorescence: Evidence for succinimide induced polar associations in an apolar solvent

A maleated ethylene-propylene copolymer (EP-MAH) was labelled with 1-naphthalene- and/or 1-pyrenemethylamine to yield an EP copolymer bearing succinimide pendants all labelled with a chromophore. The labelled EPs were reacted with LiAlH₄ so that the polar succinimide linker group between the EP backbone and the chromophore was converted into apolar pyrrolidine units. The resulting products were purified through a gel permeation chromatography column to remove the cleaved off chromophores. FT-IR spectroscopy revealed that after reduction, the peak assigned to the succinimide carbonyls was strongly diminished. UV-vis absorption and steady-state and time-resolved fluorescence measurements were performed in hexane and THF. The reduction of the succinimide carbonyls was found to have a significant effect on the luminescence properties of the labelled EPs. The polar associations taking place between the succinimide moieties in hexane were found to be dramatically decreased after reduction as shown by UV-vis absorption, steady-state excitation and emission fluorescence, time-resolved fluorescence, and fluorescence resonance energy transfer. These results demonstrate that the presence of pyrene aggregates for EP-MAH labelled with 1-pyrenemethylamine is due primarily to the polar succinimide moieties rather than the aromatic pyrene.     

ENHANCED WATER SORPTION OF A SEMI-INTERPENETRATING POLYMER NETWORK (IPN) OF POLY(2-HYDROXYETHYL METHACRYLATE) (PHEMA) AND POLY(ETHYLENE GLYCOL) (PEG)

ABSTRACT

An attempt was made to enhance the water-sorption capacity of polymers of 2-hydroxyethyl methacrylate (HEMA) by preparing its semi-interpenetrating polymer network (IPN) with a hydrophilic polymer such as poly(ethylene glycol) (PEG). The effects of various factors, such as history of the polymer sample, chemical architecture of the IPN, presence of salt ions in the swelling medium, and temperature of the swelling medium, were investigated on the water sorption kinetics of the IPNs. The IPN was characterized by IR spectral analysis and various structural parameters, such as molecular weight between crosslinks (M_c), crosslink density (q) and number of elastically effective chains (V_e), were evaluated. The IPNs were also assessed for their antithrombogenic potential.     

Synthesis and photoluminescence stability of non-conjugated polymers based on fluorene and benzoxazole

A kind of non-conjugated blue luminescent polymer based on fluorene and benzoxazole was synthesized via solution condensation polymerization from 2,2-bis(3-amino-4-hydroxyphenyl)-propane and 2,7-dicarboxyl-9,9-dioctyl-fluorene and was characterized with H NMR, FT-IR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV-vis absorption and photoluminescence (PL) spectroscopy. The polymer displayed the maximum photoluminescence emission peak at 415 nm and showed high PL spectroscopic stability. The green-to-blue emission intensity ratio I_Green/I_Blue is only 0.073 even after thermal annealing at 150 °C for 30 h. After being exposed to UV light for 30 min, no bathochromic emission or obvious crosslink is observed. The common phenomenon of greenish blue emission of fluorene-based polymer around 525 nm has been effectively restrained in this polymer by introducing the isopropylidene group into the backbone of polymer.