Real-time monitoring of surface-initiated atom transfer radical polymerization using silicon photonic microring resonators: implications for combinatorial screening of polymer brush growth conditions

We directly monitor in parallel and in real time the temporal profiles of polymer brushes simultaneously grown via multiple ATRP reaction conditions on a single substrate using arrays of silicon photonic microring resonators. In addition to probing relative polymerization rates, we show the ability to evaluate the dynamic properties of the in situ grown polymers. This presents a powerful new platform for studying modified interfaces that may allow for the combinatorial optimization of surface-initiated polymerization conditions.     

Combinatorial method for the study of new co-fluorescence enhancement system

The new co-fluorescence enhancement system was found in polymer matrix and studied with a combinatorial approach based on Re(DBM)3phen (Re3+: Tb3+, La3+, Gd3+, Y3+; dbm: dibenzoylmethane; phen: phenanthroline) and Sm3+ complex co-doped poly(methyl methacrylate)(PMMA). We have presents a new methodology for the rapid optimization of the luminescence conditions of thin-film sample in arrays of microwells. Two libraries were generated in order to study the effect of the species and content of enhancing ions on the luminescence enhancing efficiency, respectively. At the optimal content of 20 wt.% Sm(DBM)3phen, the maximum sensitization efficiency of Tb(DBM)3phen is about nine times. The intramolecular and intermolecular energy transfer processes in rare-earth complex-doped PMMA are discussed. The energy transfer processes make the co-fluorescence effect come true. Although, the methodology described here was implemented for optimization of co-fluorescence conditions, it is can be further implemented for a variety of applications in which optimization of parameters can be studied in situ using spectroscopic tool.     

Optimization of polymerization conditions of furan with aniline for variable conducting polymers

A high-throughput multiparameter optimization of chemical oxidative polymerization conditions has been developed for a facile synthesis of furan homopolymers and furan/aniline copolymers using a combinatorial method. The polymerization yield, molecular structure, and properties of the polymers would be optimized against typical polymerization parameters, including oxidant species, medium species, temperature, oxidant/monomer ratio, monomer concentration, dopant concentration, and furan/aniline comonomer ratio. The electrical conductivity, lead ion adsorptivity, chemical resistance, and thermal behavior of the polymers were also elaborated. It is found that only a combination of FeCl(3) and nitromethane as oxidant and medium, respectively, is appropriate for the furan homopolymerization. The homopolymerization yield increases consistently with an increase in the monomer concentration from 0.05 to 0.2 M and the FeCl(3)/furan molar ratio from 0.25 to 1.25. Although the as-prepared polyfuran exhibits very low conductivity, down to 10(-11) S cm(-1), the HCl- and HClO(4)-doped polyfurans possess much higher conductivities of 9.2 x 10(-8) and 2.38 x 10(-5) S cm(-1), respectively. In addition, the conductivity of the furan/aniline copolymer rises steadily with increasing aniline content, although the copolymerization yield shows a minimum at the furan/aniline molar ratio of 60/40, which is evidence of the occurrence of a real copolymerization between the furan and aniline monomers. The difficulty of synthesizing conducting polyfuran could be overcome to some extent by the polymerization in an appropriate condition optimized in this study. Particularly, the difficulty of synthesizing poly(furan-co-aniline) having much higher conductivity than the polyfuran would be largely conquered by chemical oxidative copolymerization of furan with aniline.     

Conducting polymers in chemical sensors and arrays

The review covers main applications of conducting polymers in chemical sensors and biosensors. The first part is focused on intrinsic and induced receptor properties of conducting polymers, such as pH sensitivity, sensitivity to inorganic ions and organic molecules as well as sensitivity to gases. Induced receptor properties can be also formed by molecularly imprinted polymerization or by immobilization of biological receptors. Immobilization strategies are reviewed in the second part. The third part is focused on applications of conducting polymers as transducers and includes usual optical (fluorescence, SPR, etc.) and electrical (conductometric, amperometric, potentiometric, etc.) transducing techniques as well as organic chemosensitive semiconductor devices. An assembly of stable sensing structures requires strong binding of conducting polymers to solid supports. These aspects are discussed in the next part. Finally, an application of combinatorial synthesis and high-throughput analysis to the development and optimization of sensing materials is described.     

Continuous flow enzyme-catalyzed polymerization in a microreactor

Enzymes immobilized on solid supports are increasingly used for greener, more sustainable chemical transformation processes. Here, we used microreactors to study enzyme-catalyzed ring-opening polymerization of ε-caprolactone to polycaprolactone. A novel microreactor design enabled us to perform these heterogeneous reactions in continuous mode, in organic media, and at elevated temperatures. Using microreactors, we achieved faster polymerization and higher molecular mass compared to using batch reactors. While this study focused on polymerization reactions, it is evident that similar microreactor based platforms can readily be extended to other enzyme-based systems, for example, high-throughput screening of new enzymes and to precision measurements of new processes where continuous flow mode is preferred. This is the first reported demonstration of a solid supported enzyme-catalyzed polymerization reaction in continuous mode.     

High‐Output Polymer Screening: Exploiting Combinatorial Chemistry and Data Mining Tools in Catalyst and Polymer Development

High‐output polymer screening (HOPS) combines automated polymerization with online reaction monitoring, rapid polymer characterization and novel fingerprint technology useful in polymer preparation as well as polymer processing and polymer additive development. Originally, HOPS was introduced to develop polymerization catalysts and polyolefin materials more effectively. In comparison to conventional high‐throughput screening, focusing on ultrahigh speed of catalyst screening using arrays of miniaturized reactors, output‐oriented, process‐relevant HOPS is aiming at generating and exploiting high information density (useful information/experiment). Catalyst systems for olefin polymerization are evaluated in automated workstations with multiparallel as well as semi‐ and fully automated, upgraded lab reactors. Automated polymerizations under standardized conditions afford large families of well‐characterized polymers which serve as calibration samples for data analysis. Data analysis, using multivariate calibration, is the key to basic correlations between spectroscopic information and catalyst and polymer properties as well as reaction parameters and processing conditions. IR spectroscopic fingerprints are used to measure chemical copolymer composition, density, molecular weight as well as thermal and even mechanical properties. This fingerprint technology can be applied in online quality control and facilitates transfer from lab results into pilot and production plants. Fingerprint methods are important components of rapid online analysis and can reduce the need for time‐ and money‐consuming polymer testing.

Fingerprint technology combines spectroscopic analysis by means of “cheap” spectrometers with multivariate calibration.     

Binding behaviour of molecularly imprinted polymers prepared by a hierarchical approach in mesoporous silica beads of varying porosity

One of the most interesting methods for preparing molecularly imprinted polymers with controlled morphology consists in filling the pores of silica beads with an imprinting mixture, polymerizing it and dissolving the support, leaving porous imprinted beads that are the "negative image" of the silica beads. The main advantage of such an approach consists in the easy preparation of spherical imprinted polymeric particles with narrow diameter and pore size distribution, particularly indicated for chromatographic applications. In this approach it has been shown that the resulting morphology of polymeric beads depends essentially on the porosity and surface properties of the silica beads that act as microreactors for the thermopolymerization process. Anyway, it is not yet clear if the porosity of the silica beads influences the binding properties of the resulting imprinted beads. In this paper, we report the effect of different porosities of the starting mesoporous silica beads on the resulting binding properties of imprinted polymers with molecular recognition properties towards the fungicide carbendazim. The morphological properties of the imprinted beads prepared through this hierarchical approach were measured by nitrogen adsorption porosimetry and compared with a reference imprinted material prepared by bulk polymerization. The chromatographic behaviour of HPLC columns packed with the imprinted materials were examined by eluting increasing amounts of carbendazim and extracting the binding parameters through a peak profiling approach. The experimental results obtained show that the resulting binding properties of the imprinted beads are strongly affected by the polymerization approach used but not by the initial porosity of the silica beads, with the sole exception of the binding site density, which appears to be inversely proportional to them.     

Fourier transform infrared imaging for high-throughput analysis of pharmaceutical formulations

Fourier transform infrared (FTIR) spectroscopic imaging with infrared array detectors has recently emerged as a powerful materials characterization tool. We report a novel application of FTIR imaging for high-throughput analysis of materials under controlled environment. This approach combines the use of spectroscopic imaging with an attenuated total reflection (ATR)-IR cell, microdroplet sample deposition system, and a device that controls humidity inside the cell. By this approach, it was possible to obtain "chemical snapshots" from a spatially defined array of many different polymer/drug formulations (more than 100) under identical conditions. This method provides direct measurement of materials properties for high-throughput formulation design and optimization. Simultaneous response (water sorption, crystallization, etc.) of the array of formulations to the environmental parameters was studied. Implications of the presented approach range from studies of smart polymeric materials and sensors to screening of pharmaceuticals and biomaterials.     

High chemical and solvent resistant,branched terpene methacrylate polymers—Preparation,thermal properties,and decomposition mechanism

Branched terpene methacrylate polymers under UV‐polymerization process of methacrylates prepared based on naturally occurring terpene alcohols such as geraniol, nerol, and citronellol have been obtained. Amine catalysed reaction of geraniol, nerol, or citronellol with methacryloyl chloride allowed obtaining terpene methacrylate monomers with high yield. Their structure was confirmed by spectroscopic methods (¹HNMR, ¹³CNMR, ATR‐FTIR). The structure of the resulting polymers was evaluated by applying the ¹³C/CP MAS and ATR‐FTIR. The chosen physicochemical properties such as chemical resistance, solvent resistance, and thermal properties in inert and oxidative atmospheres have been studied. In addition, the detailed pyrolysis and oxidative degradation mechanism by applying the TG/DSC/FTIR/QMS‐coupled method was evaluated. The results indicated the potential application of novel, branched terpene methacrylate polymers for manufacturing products which could be utilized under corrosive conditions, due to their high resistance in both acidic and basic environments and different polarity solvents, as well as satisfactory thermal resistance.     

A Comparative Study on HCN Polymers Synthesized by Polymerization of NH4CN or Diaminomaleonitrile in Aqueous Media: New Perspectives for Prebiotic Chemistry and Materials Science

HCN polymers are a group of complex and heterogeneous substances that are widely known in the fields of astrobiology and prebiotic chemistry. In addition, they have recently received considerable attention as potential functional material coatings. However, the real nature and pathways of formation of HCN polymers remain open questions. It is well established that the tuning of macromolecular structures determines the properties and practical applications of a polymeric material. Herein, different synthetic conditions were explored for the production of HCN polymers from NH₄CN or diaminomaleonitrile in aqueous media with different concentrations of the starting reactants and several reaction times. By using a systematic methodology, both series of polymers were shown to exhibit similar, but not identical, spectroscopic and thermal fingerprints, which resulted in a clear differentiation of their morphological and electrochemical properties. New macrostructures are proposed for HCN polymers, and promising insights are discussed for prebiotic chemistry and materials science on the basis of the experimental results.     

Optimization of direct arylation polymerization (DArP) through the identification and control of defects in polymer structure

As a newly emerged protocol for the synthesis of conjugated polymers, direct arylation polymerization (DArP) is an environmentally friendly and cost-effective alternative to traditional methods of polymerization. DArP efficiently yields conjugated polymers with high yield and high molecular weight. However, DArP is also known to produce defects in polymer chemical structure. Together with molecular weight and polydispersity, these defects are considered to be important parameters of polymer structure and they have a strong impact on optical, electronic and thermal properties of conjugated polymers. The four major classes of conjugated polymer defects inherent for DArP have been identified: homocoupling regiodefects, branching defects, end group defects, and residual metal defects. To have a precise control over the polymer properties, it is important to understand what causes the defects to form during the polymerization process and be able to control their content. Here within the scope of current literature, we discuss in detail the definition and origin of all these defects, their influence on polymer properties and effective means to control the defects through fine tuning of the DArP reaction parameters. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 135–147     

Continuous flow techniques in organic synthesis

As part of the dramatic changes associated with the need for preparing compound libraries in pharmaceutical and agrochemical research laboratories, the search for new technologies that allow automation of synthetic processes has become one of the main topics. Despite this strong trend for automation high-throughput chemistry is still carried out in batches, whereas flow-through processes are rather restricted to production processes. This is far from understandable because the main advantages of that approach are facile automation, reproducibility, safety, and process reliability, because constant reaction parameters can be assured. Indeed, methods and technologies are missing that allow rapid transfer from the research level to process development without time-consuming adaptation and optimization of methods from the laboratory scale to production plant scale. Continuous-flow processes are considered as a universal lever to overcome these restrictions and, only recently, joint efforts between synthetic and polymer chemists and chemical engineers have resulted in the first continuous-flow devices and microreactors; these allow rapid preparation of compounds with minimum workup. Many of these approaches use immobilized reagents and catalysts, which are embedded in a structured flow-through reactor. It is generally accepted, that for achieving best reaction and kinetic parameters for convective-flow processes monolithic materials are ideally suited as solid phases or polymer supports. In addition, immobilization techniques have to be developed that allow facile regeneration of the active species in the reactor.     

A Methodology for Estimating Kinetic Parameters and Reactivity Ratios of Multi‐site Type Catalysts Using Polymerization,Fractionation, and Spectroscopic Techniques

This work describes a polymer reaction engineering framework for understanding how catalyst kinetic parameters affect the microstructure of polyolefins made with single‐ or multi‐site catalysts. Moreover, a methodology for deconvolution and kinetic parameters estimation is presented to estimate the reactivity ratios of multi‐site catalysts based on the combination of polymerization, fractionation, and spectroscopic techniques, namely, gel permeation chromatography‐IR and carbon‐13 nuclear magnetic resonance spectroscopy. The methodology capabilities are then demonstrated and validated using a case study simulated via a Monte Carlo model including random noise in order to better represent experimental result uncertainties. The methodology can reverse engineer experimental results and estimate all relevant reaction performance parameters.     

Monte Carlo simulation on rate enhancement of nitroxide‐mediated living free‐radical polymerization

Four rate enhancing cases of nitroxide‐mediated living free‐radical polymerizations are simulated by the Monte Carlo method to investigate the effects of parameters on kinetics and molecular weight distribution of the resulting polymers. In all cases the equilibrium between growing and dormant chains shifts in favor of the growing chains under corresponding reaction conditions. The polymerization rates are therefore increased substantially without much loss in control of molecular weight and distribution of the products. The optimization of rate‐enhancement in living free‐radical polymerization is also discussed.     

Generation and Reaction of Functional Alkyllithiums by Using Microreactors and Their Application to Heterotelechelic Polymer Synthesis

Flow microreactors enabled the successful generation of various functional alkyllithiums containing electrophilic functional groups, as well as the use of these alkyllithiums in subsequent reactions. The high reactivity of these series of reactions could be achieved by the extremely accurate and selective control of residence time. Moreover, integrated flow microreactor systems could be used to successfully synthesize heterotelechelic polymers with two functionalities, one at each end, via a process involving controlled anionic polymerization initiated by functional alkyllithium compounds, followed by trapping reactions with difunctional electrophiles.     

Linear aminophenol polymers using the mannich reaction

Mannich reactions were used to prepare a series of low-molecular-weight linear polymers from substituted phenols, formaldehyde, and secondary diamines. The physical and spectroscopic properties of these new aminophenol polymers are described and compared with those of the bisphenolic diamines formed as an intermediate step in the polymerization process. The polymers were found to give coloured, water-soluble, metal complexes with copper and iron salts.     

Novel Surface Modification of Sulfur by Plasma Polymerization and its Application in Dissimilar Rubber-Rubber Blends

In this study, surface modification of elemental sulfur by plasma polymerization with acetylene, perfluorohexane and acrylic acid is described, with the aim of changing the surface properties of sulfur without losing the bulk properties and reactivities in the vulcanization process. Significant improvements are obtained in dissimilar elastomer blends using the encapsulated sulfur powders. The conditions for the plasma polymerization were varied in order to obtain the optimal performance of the modified sulfur. The imperfections in the shell structure, obtained with plasma polymers, act as gateways to release sulfur for the vulcanization reaction.     

Simulation of conversion profiles and temperature distributions within dimethacrylate thick material during photopolymerization

Photoinitiated polymerization of multifunctional monomers is an usual method to prepare highly crosslinked networks which have a wide variety of applications. This method leads to high reaction rates and the resulting exothermic effect of this reaction can be the cause of defects in the final material. The heterogeneities alter greatly the physical properties of ultimate products, particularly the optical ones, what causes problems in the design of thick and optically perfect materials. The knowledge of the conversion profile and the temperature distribution within the material during the photopolymerization is useful for the process optimization. Unfortunately, these parameters cannot be measured during the process. Thus, we decided to simulate them. Firstly, the necessary parameters (like conversion and reaction rate) were measured on thin material in isothermal conditions by photocalorimetry. Secondly, these kinetic data were used in a computational calculation to obtain the conversion profile and the temperature distribution within dimethacrylate thick material. The calculated temperature and conversion-time curves are in good agreement with the experimental curves determined under the same conditions.     

Novel synthesis of photocrosslinkable polymers

A new preparative route to photocrosslinkable polymers in which the polymers are produced directly from the polymerization of vinyl monomers having photocrosslinkable groups has been investigated. The photosensitive resins thus produced have higher sensitivity and resolution than conventional photosensitive resins. The monomers were synthesized from the esterification of vinylphenols or vinyl β-chloroethyl ether with cinnamic acid, β-styrylacrylic acid, and their homologs, and from the etherification of vinyl β-chloroethyl ether with hydroxychalcones. Homopolymerizations of these monomers and their copolymerizations with other comonomers were investigated with the use of both radical and ionic initiators. It is shown that radical polymerization of the monomers gave soluble polymers only at low conversion. Anionic initiators did not initiate polymerization. Cationic polymerization imparted soluble polymers in high yield, except for the monomers bearing cyano groups, which generally gave insoluble polymers. Infrared and NMR spectroscopic investigation of the cationically obtained soluble polymers and comparative investigation by cationic polymerization of model compounds indicated that polymerization of the monomers proceeds through the vinyl double bond without affecting the photosensitive unsaturated bond. Thus, linear photocrosslinkable polymers with an intact photoreactive group may be produced by cationic polymerization. In general, these polymers have uniform structure and modifiable physical properties depending on the monomer used. The polymer thus obtained from β-vinyloxyethyl cinnamate has been shown to have excellent properties for use as a photo-resist.