Hybrid polyacrylamide chiral stationary phases for HPLC prepared by surface-initiated photopolymerization

Two hybrid polyacrylamide chiral stationary phases (CSPs) for HPLC have been synthesized by a new surface-initiated photo-induced radical polymerization approach of enantiopure N,N'-diacryloyl derivatives of (1R,2R)-diaminocyclohexane (CSP1) and (1R,2R)-diphenylethylenediamine (CSP2). This system is based on the activation of mesoporous silica microparticles by chemically bonded trichloroacetyl groups and dimanganese decacarbonyl as catalyst. UV irradiation was performed using a lab-made quartz photochemical reactor, ad hoc designed for the photo-induced polymerization process on the surface of microparticles. The two phases were evaluated and compared as chromatographic supports for the enantioselective HPLC of model chiral compounds. Their physico-chemical properties and chromatographic performances were also evaluated in comparison with those exhibited by the homologue CSPs obtained by the grafting-from thermal-induced process (CSP3 and CSP4). The new photopolymerization approach yielded higher grafting density than the thermal-induced one, especially in the case of the less reactive monomer (the diacryloyl derivative of (1R,2R)-diphenylethylenediamine), good chromatographic efficiency and a broad application field under normal phase and polar organic mode conditions.     

Synthesis and properties of UV curable waterborne hyperbranched aliphatic polyester

The UV curable waterborne hyperbranched polyester (WBHP) consisting of a multi-hydroxy functional aliphatic polyester core, which is endcapped with methacrylic and salt-like groups in different ratios was synthesized. The core is second generation of hyperbranched aliphatic polyester Boltorn™ H20 with approximately 16 hydroxyl groups. The effects of different ratios of chemical structure of end groups were studied by evaluating various properties of WBHP such as solubility in water, dynamic viscosity, UV curing rate and final unsaturation conversion. A natural good control over the solubility of the samples was possible by salt-like functionality and raising the temperature. The investigation of solubility characteristics of the modified hyperbranched polyester illustrated that those with higher concentration of salt-like moiety were more soluble while those of having lower salt-like moiety were less soluble. The viscosity of the resin WBHP was reduced rapidly by dilution with water and raising temperature. Water showed a favorable viscosity reduction effect as compared to monomer and its blend with water. The polymerization rate of the resins under UV irradiation in the presence of a photoinitiator showed an increasing trend with higher concentration of methacrylate functionality.     

Synthesis and properties of a novel hyperbranched polyphosphate acrylate applied to UV curable flame retardant coatings

A series of hyperbranched polyphosphate acrylates (HPPAs) being used for UV curable flame retardant coatings were prepared by the reaction of tri(acryloyloxyethyl) phosphate (TAEP) with piperazine at given ratios, and characterized using FTIR, ¹H NMR and GPC measurements. HPPA was blended with TAEP in different ratios to obtain a series of UV curable resins. Their maximum photopolymerization rates and final unsaturation conversion (P^f) in the cured films at the presence of a photofragmenting initiator were investigated. The results showed that the P^f increased along with HPPA content and the pure HPPA has the maximum value of 82.1% in the photo-DSC analysis. The data from dynamic mechanical thermal analysis showed that HPPA has good miscibility with TAEP. The crosslinking density and T_g of the cured film decrease along with the content of HPPA in the blend. The mechanical properties of the cured films were also investigated. Less than 20% HPPA addition improved both the tensile strength and elongation at break without damaging the modulus. The HPPA₂₀TAEP₈₀ film with 20% HPPA addition has the highest tensile strength of 31.7 MPa and an elongation at break two times that of cured TAEP. The flame retardancy of the UV cured films was investigated by the limiting oxygen index (LOI). The cured TAEP/HPPA samples greatly expanded when burning, and the degree of expansion increased along with HPPA content. However, the LOI values decreased from 47.0 to 34.0 along with HPPA content, which can be ascribed to that the flame retardancy of TAEP is mainly acting in the gas phase, whereas HPPA mainly acting in condensed phase, and the gas phase mechanism holds the dominant effect while their blends are burning.     

Fabrication of glucose biosensor for whole blood based on Au/hyperbranched polyester nanoparticles multilayers by antibiofouling and self-assembly technique

Acknowledging the benefits of hyperbranched polymers and their nanoparticles, herein we report the design and synthesis of sulfonic acid group functionalized hydroxyl-terminated hyperbranched polyester (H30-SO₃H) nanoparticles and their biomedical application. The H30-SO₃H nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance spectroscopy (¹H NMR). The good hemocompatibility of H30-SO₃H nanoparticles was also investigated by coagulation tests, complement activation and platelet activation. The novel glucose biosensor was fabricated by immobilizing the positively charged Au nanoparticles, H30-SO₃H nanoparticles and glucose oxidase (GOx) onto the surface of glassy carbon electrode (GCE). It can be applied in whole blood directly, which was based on the good hemocompatibility and antibiofouling property of H30-SO₃H nanoparticles. The biosensor had good electrocatalytic activity toward glucose with a wide linear range (0.2–20 mM), a low detection limit 1.2 × 10⁻⁵ M in whole blood and good anti-interference property. The development of materials science will offer a novel platform for application to substance detection in whole blood.     

Synthesis of multi-arm star polystyrene with hyperbranched polyether core

Multi-arm star polystyrenes with hyperbranched poly(3-ethyl-3-oxetanemethanol) (PEOM, 3) core were synthesized by atom transfer radical polymerization (ATRP) method. The structures of polymers were confirmed by FT-IR and ¹H NMR. GPC results showed that the resultant polymers had relatively low polydispersity indices (PD = 1.47-2.03). DSC analysis indicated that polystyrene star polymers had a glass transition temperature (T_g = 42.2-91.5 °C) that changed with the amount of the polystyrene in the polymers. In addition, the aggregation behavior of the multi-arm star polystyrenes in a selective solvent (THF/cyclohexane) was probed with polystyrene arms that encapsulated in the aggregates and PEOM cores hidden in the center of the micelles.     

A novel hyperbranched copolymer constituted of triphenylamine and divinyl bipyridyl units

A hyperbranched copolymer (HTP) containing triphenylamine and divinyl bipyridyl units has been synthesized via Heck coupling reaction from 5,5′-divinyl-2,2′-bipyridyl and tris(4-bromophenyl)amine. The polymer had a number-average molecular weight of 1895 and a weight-average molecular weight of 2315, and was readily soluble in common organic solvents, such as THF, DMF and chloroform. The chemical structure of HTP was confirmed by FT-IR, ¹H NMR. Its thermal, electrochemical and optical properties have been investigated. The thermal analysis revealed that the polymer had a good thermal stability with the onset decomposition temperature at ca. 267 °C. The Uv-vis absorption and photoluminescence (PL) spectra exhibited that the Stokes shift between the absorption and emission of HTP was relatively large: 103 for HTP solution and 135 nm for HTP film. The electrochemical analysis showed that the electrochemical band gap of HTP was 0.92 eV. The fluorescence of the polymer in solution can be quenched by various transition metal ions and HTP showed different sensitivity in transition metal ions sensing.     

A natural component as initiator for photopolymerization of 1,6-hexanedioldiacrylate

1,3-Benzodioxole (BDO) as a simple model compound for the BDO derivatives from natural plant was used as coinitiator for p-chlorobenzophenone (CBP) and initiator for UV photopolymerization of 1,6-hexanedioldiacrylate (HDDA), respectively. The results showed that, BDO was an effective coinitiator for CBP. Although BDO as initiator led to very low rate of polymerization, it was still meaningful for the photocuring field.     

Porous membranes modified by hyperbranched polymers: I. Preparation and characterization of PVDF membrane using hyperbranched polyglycerol as additive

Porous membranes were prepared via phase inversion process from casting solution composed of poly(vinylidene fluoride) (PVDF), N,N-dimethylacetamide (DMAc), and hyperbranched polyglycerol (HPG). The membranes were characterized in terms of surface and bulk chemical compositions, morphology, water contact angle, porosity, and water flux. The effects of HPG content on membrane structures and properties were investigated. The effect of HPG addition on the hydrophilicity was discussed as well when the compositions of coagulation bath were changed. To better understand the special effects of HPG on the structures and properties of the membranes, PVDF membranes prepared using HPG as the additive were compared with those prepared using polyethylene glycol (PEG) as the additive.     

Synthesis of monodisperse polymer microspheres by photopolymerization of microdroplets

We have examined photopolymerization of highly monodisperse microdroplets of monomer solutions under UV-light radiation. Microdroplets were generated using a modified vibrating aerosol generator, and the diameter of the droplets can be tuned to any size between 5 to 100 m. Polymer particles derived from the droplets were characterized by optical microscopy and SEM. The results show that the polymer particles, under optimum conditions, can be highly spherical and monodisperse. The diameter and morphology of resulting microspheres depend on the diameter of the monomer solution droplets, monomer concentration, photopolymerization reaction temperature, residence time, and droplet dispersion.     

Thermal properties and ionic conductivity of a polymer prepared by the in situ photopolymerization of a vinylimidazole monomer containing a mesogenic group

We have synthesized liquid crystalline polymers containing an imidazolium salt moiety and a mesogenic group by the in situ photopolymerization of a liquid crystalline vinylimidazole monomer in order to investigate the relationship between their thermal properties and ionic conductivity. A smectic phase was shown by the vinylimidazole monomer. The in situ photopolymerization of the monomer was carried out in the temperature range of the smectic phase. The polymer thus prepared displayed a highly ordered smectic phase in the temperature range between room temperature and about 200°C. The ionic conductivity of the polymer increased with increasing temperature. Anisotropic ionic conductivity behavior was observed for the polymer. The ionic conductivity of the polymer aligned homogeneously is larger than when homeotropically aligned.     

Novel preparation of monolithic imprinted columns for electrochromatographic separation by photopolymerization

A monolithic molecularly imprinted polymer with specific recognition ability for 4-hydroxybenzoic acid (4-HBA) was prepared by in situ photopolymerization, using methacrylic acid (MAA) as a functional monomer, ethylene glycol dimethacrylate (EDMA) as a cross-linking agent, toluene and isooctane as porogenic solvents and Irgacure 1800 as an initiator. Baseline separation of isomers of hydroxybenzoic acid was achieved in less than 8 min on this monolithic column using 4-HBA as template, but not on the blank polymer. Furthermore, some neutral compounds could also be baseline-separated on the imprinted polymer column in the mode of pressure-driven capillary electrochromatography.     

BDC作为Iniferter引发苯乙烯聚合的研究

本文研究了由BDC(N,N-二乙基二硫代氨基甲酸苄酯)作为Iniferter(引发-转移-终止剂)引发苯乙烯的光聚合反应。发现转化率和分子量均随时间逐步增大,反应生成带有起始功能端基的聚合物。从顺磁谱可见BDC在光照射下分解生成的小分子自由基[·SSCN-(C_2H_5)_2]及较活泼的苄基自由基引发苯乙烯聚合产生的大分子增长自由基。探讨了这种活性自由基聚合反应机理。     

Crystallization kinetics of polypropylene with hyperbranched polyurethane acrylate being used as a toughening agent

The crystallization kinetics of polypropylene (PP) with hyperbranched polyurethane acrylate (HUA) being used as a toughening agent was studied by isothermal and nonisothermal differential scanning calorimetry (DSC). The presence of a small amount of HUA (2-7%) remarkably influences the crystallizability of PP. An addition of HUA leads to an increase in the number of effective nuclei, thus resulting in an increase of crystallization rate and a stronger trend of instantaneous three-dimensional growth. For isothermal crystallization, Avrami exponents were determined to be about 2.97 for pure PP and 3.51 for the HUA/PP blend containing 5% HUA (HUA-PP). The half crystallization time (t_1/2) of pure PP was measured to be 8.43 min, while being 3.28 min for HUA-PP at the crystallization temperature of 132 °C. The nonisothermal crystallization kinetics of HUA/PP blends was analyzed by Avrami, Ozawa and Kissinger methods. It has also been proved that an addition of HUA could increase the crystallization rate of PP. Moreover, the crystallization activation energies of pure PP and HUA-PP were estimated by Kissinger and Friedman methods.     

Curcumin,a natural colorant as initiator for photopolymerization of styrene: kinetics and mechanism

The photopolymerization of styrene in presence of an efficient, eco-friendly, and a cost-effective photoinitiator, curcumin, which is found in turmeric root, has been reported for the first time. The catalytic concentration (10⁻⁶ M) of curcumin is effective to photoinitiate the polymerization of styrene. The kinetic data, inhibiting effect of benzoquinone and electron spin resonance studies, indicate that the polymerization proceeds via a free radical mechanism. The system follows non-ideal kinetics (R _p ∝ [Cur]^0.36 [Sty]^1.04) due to both primary radical termination and degradative chain transfer reactions. The broad peaks due to methine and methylene protons in ¹H-NMR (nuclear magnetic resonance [NMR]) spectrum and a band of resonances at 145–146 ppm in ¹³C-NMR indicate atactic nature of the polystyrene formed. The maximum conversion at 30 ± 0.2 °C in 17 h has been limited to 23% without gelation. The formation of radicals and mechanism of polymerization are also discussed.     

Use of 3-hydroxyflavone as a fluorescence probe for the controlled photopolymerization of the E-Shell 300 polymer

Photopolymerization process of the photo-reactive acrylate-based E-Shell 300 biocompatible polymers doped with 3-hydroxyflavone (3-HF) molecules have been studied. It was found that the spectra of these complexes manifest two intensive fluorescence bands, the short-wavelength band of the E-Shell 300 autofluoresence and the long-wavelength emission band of the probe tautomer.The intensity and the relative quantum yield of 3-HF long-wavelength green band grew by 1.8 times during polymerization. They were characterized by continuous and single-valued response function to the polymerization progress. The function may be used as an indicator suitable for photopolymerization monitoring.Moreover, time-resolved measurements of the emission lifetimes showed significant difference between 3-HF emission lifetime in low viscous solvent (0.9 ns)) and in polymerized sample (3.2 ns)) which also can be applied in control of photopolymerization. 3-HF is a relatively cheap, non-toxic and has good solubility in the polymer media we chose.     

Synthesis of fluorinated hyperbranched polymers capable as highly hydrophobic and oleophobic coating materials

A series of coating materials were prepared from two classes of hyperbranched polymers containing short fluorocarbon chains (HPEFs/HPUFs). The obtained hyperbranched polymers were characterized by FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, GPC and TG analyses. HPEFs/HPUFs exhibited very low surface free energies (13.67-24.49 mJ/m²) which almost are independent of their internal backbone but dependent on the terminal fluorocarbon chains. Highly hydrophobic and/or oleophobic surfaces of cotton woven fabric can be achieved from these polymers by solution-immersion coating method. The static and dynamic wettabilities of the HPEFs/HPUFs treated fabrics have been investigated. The static contact angles reached to 146°, 122° and 102° for water, hexadecane and decane, respectively. The lowest contact angle hysteresis reached to 5.9°.     

Pervaporation properties of EC membranes modified by aliphatic hyperbranched polyester

Pervaporation membranes containing hyperbranched polymer were prepared from the blends of ethyl cellulose (EC) and hyperbranched polyester (HBPE). The FT-IR analysis indicated that the interactions between EC and HBPE decreased as increasing the generation of HBPE. The membrane containing HBPE (EC-HBPE) showed both higher sorption ratio and selectivity than pure EC membrane. The effects of HBPE content as well as temperature of feed solutions on the membrane performance were investigated in detail. The EC-HBPE membrane exhibited much higher permeate flux than the EC membrane, while the separation factor maintained at same level.     

Investigation of thermodynamic properties of hyperbranched aliphatic polyesters by inverse gas chromatography

Thermodynamic properties of a series of commercial hyperbranched aliphatic polyesters (Boltorn^® H20, H30 and H40) were examined for the first time by inverse gas chromatography (IGC) using 13 different solvents at infinite dilution as probes. Retention data of probes were utilized for an extensive characterization of polymers, which includes the determination of the Flory–Huggins interaction parameter, the weight fraction activity coefficient as well as the total and partial solubility parameters. Analysis of the results indicated that the total and partial solubility parameters decrease with increase of temperature. Furthermore, upon increase of the molecular weight, while the hydrogen bonding component decreases, no influence on the total solubility parameter is noticed within the experimental error margins. Results from the present study while providing new insight to the thermodynamic characteristics of the examined systems, they are also expected to reflect more general aspects of the behavior of hyperbranched polymers bearing similar end-groups.     

The effects of primary amine catalyzed thio-acrylate Michael reaction on the kinetics, mechanical and physical properties of thio-acrylate networks

Thio-acrylate networks were prepared using two methods. The first method involved the in-situ photopolymerization of a multifunctional thiol mixed with a multifunctional acrylate in the presence of a photoinitiator (photo-cure only), while the second method utilized an extremely efficient thio-acrylate Michael reaction followed by the photopolymerization of unreacted acrylate functional groups (amine catalysis/photo-cure). The thio-acrylate Michael reaction was catalyzed by a primary amine that promoted a rapid 1-to-1 Michael addition reaction of thiol to acrylate. Kinetic analysis via real-time infrared (RTIR) spectroscopy verified the 1-to-1 addition, the rates of the thio-acrylate Michael reaction and the total incorporation of the thiol into the networks at various concentrations when the amine catalyst was used. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) data show very narrow glass transition temperatures for the networks prepared when the amine catalysis/photo-cure sequence was used. The two step sequential process can be used to target network films that can be tailored to have high energy damping properties at a given temperature, e.g., room temperature. Finally, in all cases, whether the photo-cure only or the amine catalysis/photo-cure process was used, the glass transition temperature increased with the initial acrylate feed concentration.     

Synthesis of spherical microcapsules by photopolymerization in aerosols

 The preparation of polymer microcapsules of well defined size in the range of 10–50 μm with different shell thickness to core diameter ratios is described. An aerosol of monodisperse droplets of a homogeneous ternary liquid system which contained a hydrophobic component and a hydrophilic component dissolved in a high-volatile mutual solvent, was produced by dispersing with a vibrating-orifice aerosol generator. After the evaporation of the solvent in a nitrogen atmosphere the particles demix and form a two-phase droplet of core-shell type. These droplets were illuminated with UV light and polymerized to highly monodisperse microcapsules with a solid polymer shell and a liquid core. The properties of the resulting particles (size, size distribution, shell thickness, shape and surface characteristics) were investigated by scanning electron microscopy, Raman spectroscopy on single optically levitated particles, and confocal Raman micro spectroscopy. The microcapsules were highly monodisperse and have spherical shape. Received: 24 July 1996 Accepted: 29 August 1996