Using MESIMS to analyze polymer MALDI matrix solubility

The development of reliable sample preparation methods has been critical to the success of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry experiments. Good MALDI sample preparation for polymers involves choosing the solvent system, the matrix, and the ionization agent correctly, and combining them in a manner that will lead to a sample that will produce the desired ions. The vast diversity of chemistry available in industrial polymers has challenged our ability to design reliable sample preparation methods. In the experiments reported here, we show that matrix-enhanced secondary ion mass spectrometry (MESIMS) is an effective analytical technique to explore sample segregation in solid phase MALDI samples. Qualitative comparison of MESIMS and MALDI results for polymer samples prepared with multiple matrices aids our investigation of the solid-phase solubility of a variety of low molecular weight polymer materials. Including the solid-phase solubility with the liquid-phase solubility of the polymer samples and the matrices enables the construction of a relative solubility chart, which shows the best solubility matches between the polymer and matrix materials for MALDI experiments.     

Synthesis of cyclic polybutadiene via ring-opening metathesis polymerization: the importance of removing trace linear contaminants

The synthesis of cyclic polybutadienes using ring-opening metathesis polymerization (ROMP) was accomplished. A cyclic Ru alkylidene catalyst, where a terminal ligand was covalently linked to the Ru alkylidene, was used to polymerize either 1,5-cyclooctadiene (COD) or 1,5,9-trans-cis-trans-cyclododecatriene (CDT). Trace amounts of an acyclic impurity, 4-vinylcyclohexene, found in the COD led to samples which were contaminated with linear polymer. In contrast, CDT, which was free of the impurity, afforded pure cyclic polymer. These results provide a convenient method for discerning samples of pure cyclic polymer from those which contain trace to large amounts of linear polymer. Furthermore, they emphasize the need to use monomers that are free of acyclic impurities when preparing cyclic polymers using ROMP.     

Characterization of surface plasmon energy transduction in gold nanoparticle/polymer composites by photo-DSC

In this study, we investigate the formulation and optimization of stimulus-responsive composites consisting of gold nanoparticles in polyethylene glycol diacrylate (PEGDA) matrices, which can be remotely heated through localized surface plasmon resonance (SPR). In these materials, laser radiation is absorbed by the nanoparticles and transduced into thermal energy. Optothermal properties of the polymer/nanoparticle composites are characterized using an adaptation of photo-differential scanning calorimetry (photo-DSC), in which a sample is characterized in isothermal mode in the presence and absence of optical illumination. Au/PEGDA composite samples are determined by photo-DSC to transduce energy from a 532 nm optical source with high efficiencies (>80%). UV/Vis/NIR spectrophotometry is used to characterize the optical properties of the samples. Nanoparticle dispersion and size within composite polymer matrices are characterized using transmission electron microscopy (TEM). It is shown that the magnitude and rate of energy transduction can be tuned by varying both nanoparticle concentration and dispersion.     

Optical rotatory power of biodegradable polylactic acid films

Polylactic acid (PLA) is a polymer material on which biodegradability research has been the most advanced. PLA is a chiral polymer in which molecules containing asymmetric carbon atoms have a helical structure. Two optical isomers of PLA exist, PLLA (poly(L-lactic acid)) and PDLA (poly(D-lactic acid)). In this study, using various physical processes, we fabricated various samples such as oriented PLLA film, PLLA fiber, rolled PLLA film and forged PLLA plate. We observed a large optical rotatory power ρ in the cylindrical plate fabricated using a forging process. ρ of forged PLLA plates is 7200°/mm which is approximately 300 times larger than that of α-quartz.     

Determination of bisphenol A in environmental water at ultra-low level by high-performance liquid chromatography with an effective on-line pretreatment device

We have developed a simple HPLC method for the microanalysis of bisphenol A (BPA), which is often contained in environmental water and is known as an endocrine disrupter. HPLC coupled with electrochemical detection requires a simpler procedure of pretreatment compared to GC-MS. In this study, we analyzed BPA using molecularly imprinted polymer as an on-line pretreatment device. This polymer has molecular recognition sites and provides specific selectivity in extraction process. Due to this effect, the detection limit obtained with this HPLC was 0.36 ng/l. This method applied to environmental water and purified water samples containing 2-70 ng/l of BPA successfully. Furthermore, UV detection was performed in some actual analyses.     

The effect of thermal processing on PVC—III. Photo-oxidation of unstabilized PVC

The rate of photo-oxidation of unstabilized PVC is markedly dependent on the severity of the processing operation. In mildly processed PVC, peroxy gel appears to be a very effective photo-initiator whereas in more severely processed polymer, solvent soluble polymer containing polyconjugation, hydroperoxides and carbonyl groups is primarily responsible for photo-initiation. The auto-retardation of photo-oxidation which occurs in all samples is believed to be due to the build-up of a highly absorbing surface layer of degraded polymer.     

Gradient and patterned polymer brushes by photoinitiated “grafting through” approach

More than 2 decades of active investigations in the field of polymer brushes have revealed continuous and growing interest in different aspects of synthesis, properties, and applications of tethered polymers. In this article, we report on our recent advances in brush synthesis. The method we explore is based on the combination of “grafting through” approach with the functional anchoring polymer layer technique. We introduce the photoinitiated “version” of synthesis of polyacrylamide brushes. Both homogeneous depositions and laterally resolved gradient and patterned samples have been prepared by this technique. The results for flat polymer brushes, that is, thickness, stability, and contact angles, are complimented by kinetic parameters as deducted from analysis of gradient samples obtained by the method of a sliding mask. A microscopic shadow mask is used to fabricate patterned brushes. The microscopically patterned brushes demonstrate high lateral resolution limited by optical phenomena. Finally, we have performed a viability assaying of neuronal cell on both flat and patterned brushes. Sufficient restraint of cell adhesion on polyacrylamide photobrushes and very low cytotoxicity of the brush components (polymer brush itself, anchoring layer) make photografting a promising platform to control cell deposition and surface localization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1616–1622, 2010     

Infrared study on the interaction of poly(vinyl chloride) and ketones. I. PVC-MEK film system

In a previous article we presented preliminary information on IR spectrometric evidence for the interaction between poly(vinyl chloride) and ketones by using films with residual solvent as samples for spectrometry. This article reports detailed information on PVC–MEK film systems as compared to model compounds. The results indicate that there are “specific” interactions which were observed by a frequency shift of the carbonyl absorption of the ketone and changes on intensities of the C? Cl vibrational modes of the polymer, which are similar to the effects observed for nonpolymeric systems.     

Resistivity mapping: An example of aged conducting polymer

A simple multi-contact measurement method, which can be used to map the electrical resistivity of small disc-shaped samples of conducting polymer during temperature ageing, was examined for its resolution and accuracy. The method is based on electrical impedance tomography (EIT), which is used especially in medicine to visualise boundaries between areas having different electrical resistivities. In order to eliminate experimental errors, a computer simulation was used for testing. The time series of resistivity maps were recorded during ageing of real polymer samples. The contour maps and their time development are presented graphically and discussed.     

Gene analysis of multiple oral bacteria by the polymerase chain reaction coupled with capillary polymer electrophoresis

Capillary polymer electrophoresis is identified as a promising technology for the analysis of DNA from bacteria, virus and cell samples. In this paper, we propose an innovative capillary polymer electrophoresis protocol for the quantification of polymerase chain reaction products. The internal standard method was modified and applied to capillary polymer electrophoresis. The precision of our modified internal standard protocol was evaluated by measuring the relative standard deviation of intermediate capillary polymer electrophoresis experiments. Results showed that the relative standard deviation was reduced from 12.4–15.1 to 0.6–2.3%. Linear regression tests were also implemented to validate our protocol. The modified internal standard method showed good linearity and robust properties. Finally, the ease of our method was illustrated by analyzing a real clinical oral sample using a one‐run capillary polymer electrophoresis experiment.     

Interaction between pentaethylene glycol n-octyl ether and poly(acrylic acid): effect of the polymer molecular weight

The effect of the polymer molecular weight on the interaction between pentaethylene glycol n-octyl ether (C(8)E(5)) and poly(acrylic acid) (PAA) has been investigated by a combined experimental strategy including tensiometry, potentiometry, calorimetry, fluorescence quenching and intradiffusion (pulsed gradient spin echo-NMR) measurements. PAA samples with an average molecular weight varying in a wide range (M (w)=2000, 100,000, 250,000, and 450,000) have been considered. The measurements have been performed at constant polymer concentration (0.1% w/w) with varying surfactant molality. In all the considered systems, at low surfactant concentration, adsorption of surfactant monomers onto the polymer chain has been detected. At a C(8)E(5) molality (T(1)) independent of the PAA M (w), surfactant molecules start to aggregate, forming clusters to which the polymer co-participates. Above this concentration, the behavior of the system depends on M (w). In fact, if polymer samples with high molecular weight (M (w)100,000) are employed, all the added surfactant aggregates onto the polymer leading to the polymer saturation and, subsequently, to free micelles formation. Both saturation and free micellization occur at surfactant concentrations which are independent of the polymer molecular weight. C(8)E(5) aqueous mixtures containing PAA with low molecular weight (M (w)=2000) behaves differently, in that, above T(1), only a fraction ( approximately 20%) of the added surfactant molecules interact with the polymer, forming aggregates to which more than one PAA chain participate. In this case, C(8)E(5) free micellization occurs before polymer saturation. The experimental evidences have been interpreted in terms of the subtle balance between the various molecular interactions driving the surfactant-polymer aggregation.     

Rapid radiochemical sample preparation for alpha spectrometry using polymer ligand films

Rapid radioanalytical methods are adversely affected by many different sample-matrix interferences, which make analyzing samples a difficult and time consuming process. A new method for preparing radioactive samples for analysis by alpha spectrometry has been demonstrated. In this technique, a selective extractive ligand is immobilized in a polymer film coated on a metal surface. This polymer ligand film is then used to extract plutonium and other radioactive analytes from solution over a short period of time. The prepared substrate is then counted directly by alpha spectroscopy in a small single detector alpha spectrometer. The method has been demonstrated for the analysis of americium and plutonium in liquid samples such as water and urine.     

Palladium as catalyst in polycondensed matrix, Part III.

In this part we aim at elucidating the chemical state of palladium in the polymer cages. It was established that in samples both the adduct and the polymer exist in the forms of Pd⁰, Pd_ox and metallic Pd. Their ratio depends on the reaction conditions. Conclusions of the three parts are also given.     

Removal of residual nitrate ion from bioactive calcium silicate through soaking

Bioactive calcium silicates prepared by sol–gel routes mainly use calcium nitrate as the calcium precursor. However, the toxic nitrate ions are usually removed by calcination(i.e. 550 8C or over), which poses great challenge for the in situ preparation of inorganic/polymer composites, as polymer moieties could not survive such temperatures. In this study, we prepared 70Si30Ca(70 mol% Si O_2 and 30 mol%Ca O) bioactive glass at low temperatures where polymer could survive(i.e. 200 8C and 350 8C), and proposed to remove the residual nitrate ions through soaking. Deionized water and simulated body fluid(SBF) were employed as the soaking medium. The results showed that the residual nitrate ions could be removed as quickly as 0.5 h while maintain the bioactivity of the samples. This technique may open the possibility of preparing sol–gel derived bioactive glass/polymer hybrids in situ with reduced potential toxicity.     

Preparation of dummy template‐imprinted polymers for the rapid extraction of nonsteroidal anti‐inflammatory drugs residues in aquatic environmental samples

A molecularly imprinted polymer was synthesized and applied as a sorbent in the solid‐phase extraction device. The imprinted polymer was characterized by fourier‐transform infrared spectroscopy and scanning electron microscope. The results revealed that imprinted polymer possess sensitive selectivity and reliable adsorption properties for five NSAIDs. The imprinted polymer was successfully applied to the pre‐concentration for five NSAIDs in different water samples prior to UPLC‐MS/MS. In the early studies, several factors were investigated, including pH adjustment, the kind of elution solvent and the volume of elution solvent. Finally, we found that the pH 5 and an aliquot of 2 mL methanol were suitable for the water samples. The limits of detection and limits of quantitation of five nonsteroidal anti‐inflammatory drugs varied from 0.007 to 0.480 μg L⁻¹ and 0.03 to 1.58 μg L⁻¹, respectively. The spiking recoveries of the target analytes were 50.33‐127.64% at the levels of 0.2 μg L⁻¹, 2 μg L⁻¹ and 5 μg L⁻¹. The precision and accuracy of this method showed a great increase compared with traditional solid‐phase extraction. The developed method was successfully applied to extraction and analysis of NSAIDs in different water samples with satisfactory results which could help us better understand their environmental fate and risk to ecological health.     

Continuous Viscometric Detection in Size Exclusion Chromatography

Abstract

Continuous viscometric detection is based on the measurement of pressure drop in an on-line small capillary tube in which chromatographic eluents flow at constant flow rate. This detector is always coupled with a concentration detector (usually refractometer) and located before it to avoid back pressure in the refractometer. In order to obtain reliable information for polymer samples, it is generally necessary to connect these two detectors to a computer which performs data acquisition and treatment.

First, we discuss the problem of shape, geometry and dimensions of the viscometer. The typical characteristics are the result of a compromise between contradictory targets, mainly small internal volume, low shear rate and low pressure drop. It is shown that Poiseuille's laminar flow is only obtained when coiling radius of the measurement tube is greater than 6 cm, which is not the case inside the refractometer. Accordingly, two pressure transducers are necessary to eliminate pressure drop data coming from refractometer.

In a second part, we show how to extract information from pressure variation data. By using concentration data, pure solvent pressure and sample pressure it is possible to calculate intrinsic viscosity extrapolated to zero concentration at each point of the chromatogram. By comparison with intrinsic viscosity of the polymer used for calibration, a correction of hydrodynamic volume according to Benoit's universal calibration leads to absolute molecular weights.

In addition, for a linear polymer, the knowledge of log [η] versus log M leads to the determination of Mark-Houwink relationship coefficients. For branched polymers, viscosity laws are curved and the comparison between the linear law corresponding to the linear equivalent polymer and the experimental law allows the determination of the g' branching parameter distribution.     

Polymer induced changes of the crystallization scenario in suspensions of hard sphere like microgel particles

We investigated the crystallization scenario of highly cross linked polystyrene particles dispersed in the good solvent 2-ethylnaphtalene and their mixtures with non-adsorbing low molecular weight polysterene polymer using time resolved static light scattering. The samples were prepared slightly below the melting volume fraction of the polymer free system. For the polymer free samples, we obtained polycrystalline solids via crystallization scenario known from hard sphere suspensions with little competition of wall crystal formation. Addition of non-adsorbing low molecular weight polystyrene polymer leads to a considerably slowing down of the bulk crystallization kinetics. We observed a delay of the precursor to crystal conversion for the bulk crystallization while the induction times for the wall nucleation are reduced. The increased polymer concentration thus shifts the balance between the two competing crystallization pathways giving the possibility to tune the relative amount of wall based crystals.     

NMR observation of the conformations and motions of polymers confined to the narrow channels of their inclusion compounds

When polymers are guests in crystalline inclusion compounds (ICs) formed with small-molecule hosts, they occupy a unique environment. In a cocrystallization process the small-molecule host forms a crystalline lattice containing long narrow channels where the guest polymer chains are included. Because of the narrow channel diameter and because neighboring channels are separated by walls formed exclusively from the small-molecule host lattice, the included polymer chains are highly extended and separated from polymer chains in other IC channels. As a consequence, polymer-IC crystals provide a unique solid state environment for the included polymer chains and serve as models useful for assessing the contributions made by the inherent behavior of individual polymer chains to the properties of ordered, bulk polymers, which can be obscured by pervasive interactions between their tightly packed polymer chains. In this paper we describe the conformations and motions of polymer chains confined to the narrow channels of the following polymer-ICs: i. polyethylene and trans-1, 4-polybutadiene in their ICs with perhydrotriphenylene, ii. polyepsilon caprolactone and its diblock and triblock copolymers with polybutadiene and poly (ethylene oxide) in their ICs with urea, and iii. nylon-6 in its ICs with alpha-, beta-, and gamma-cyclodextrins. High resolution, solid state NMR serves as both the conformational (C-13 chemical shifts) and motional (relaxation times and line shapes) probe. Comparison with identical NMR measurements performed on the bulk homo- and copolymer samples permits us to draw several conclusions regarding the relationships between the conformations and motions of polymers and their dependence on their ordered solid state environments.     

Custom synthesis of molecular imprinted polymers for biotechnological application: Preparation of a polymer selective for tylosin

A molecularly imprinted polymer (MIP) selective for tylosin was designed and synthesised using a computational method (MIP “dialling”). In re-binding experiments the MIP demonstrated high affinity for tylosin in aqueous solutions and in organic solvents. The synthesised polymer was tested for re-binding with the template and related metabolites such as tylactone, narbomycin and picromycin. The HPLC analysis showed that the computationally designed polymer is specific and capable of separating the template from its structural analogues. The MIP was capable of recovering tylosin from broth samples. The polymer capacity for tylosin was estimated as 6.4 mg/g for MIP, which was suitable for practical application and tylosin recovery from broth samples. Among the advantages of this was the possibility to adsorb tylosin from a complex media with easy removal of oils and other impurities which are present in significant quantities, which can create problems for its chromatographic purification procedure. The MIP “dialling” procedure can have a general significance for the fast preparation of specific adsorbents for biotechnological applications.     

The determination of the Förster distance (R0) for phenanthrene and anthracene derivatives in poly(methyl methacrylate) films

Experiments that employ direct resonance energy transfer (DET) to obtain information about distances or domain sizes in polymer systems require independent information about the magnitude of the characteristic (F?rster) energy transfer distance R(0). Values of R(0) are relatively straightforward to obtain by the traditional spectral overlap method (R(0)(SO)) for dyes in fluid solution, but are much more difficult to obtain for dyes in rigid polymer films. Here one can obtain a value for R(0) as a fitting parameter (R(0)(FF)) for donor fluorescence decay experiments for samples containing a random distribution of donor and acceptor dyes in the polymer film. In previous experiments from our group, we needed values of R(0) for various phenanthrene (Phe, donor) and anthracene (An, acceptor) derivatives. In this paper, we describe experiments which determine R(0) values by both methods for a series of Phe-An donor-acceptor pairs in poly(methyl methacrylate) and polystyrene films. Both the location of substituents on the donor and acceptor as well as the choice of the medium had an effect on the measured R(0), which varied between 2.0 and 2.6 nm. We also ascertained that there is some unknown factor, also prevalent in the work of others, which results in the F?rster radius being larger when determined by the F?rster fit method than by the method of spectral overlap.