Influence of Microwave Irradiation on the Lipase‐Catalyzed Ring‐Opening Polymerization of ε‐Caprolactone

Summary: The microwave (MW)‐assisted lipase‐catalyzed ring‐opening polymerization of ε‐caprolactone in boiling solvents was investigated for the first time. In case of boiling toluene or benzene the MW‐assisted reaction proceeded significantly slower compared to oil bath heating. On the other hand, using boiling diethyl ether as solvent, an increase of the polymerization rate due to MW irradiation was found. Yield, molecular weight measurements, and MALDI‐TOF analysis supported the results.

Reactivity of the MW‐assisted ring‐opening polymerization of ε‐caprolactone compared with conventional thermal heating in different solvents.     

Study of the Polymerization Kinetic of Lactic Acid

Summary: Biodegradable polymers production is growing, mainly poly (lactic) acid, due to the fact that it is environmentally friendly and might be used in different fields i.e. medicine, agriculture, textiles, etc. Hence the importance of studying the polymerization process and its kinetic parameters. The polymerization process is performed by polycondensation of lactic acid using different kinds and amounts of tin based catalysts. This process is monitored during 12 hours and samples are taking for analyses every hour. Each sample is measured by gel permeation chromatography (GPC) to determine its molecular weight and by Fourier transformed infrared (FTIR) to study the evolution of alkyl absorption bands and the disappearing of hydroxyl ones. Modulated differential scanning calorimetric analysis (MDSC) is used to study the thermal behavior of every sample during each period, such as Tg displacement and changes in crystallization and melting. These data are used for the construction of the kinetic curve.     

Comparative Study of Scattering and Osmotic Properties of Synthetic and Biopolymer Gels

Summary: The effect of monovalent/divalent cation exchange on the structure and osmotic properties of chemically cross-linked polyacrylate and DNA gels swollen in near physiological salt solutions has been investigated. Both systems exhibit a reversible volume phase transition in the presence of calcium ions. The small-angle neutron scattering spectra of these gels display qualitatively similar features. At low values of q surface scattering is observed, while in the intermediate q range the signal is characteristic of scattering from rod-like elements. At high values of q the scattering intensity is governed by the local (short-range) geometry of the polymer chains. The competition between monovalent and divalent cations has been studied by anomalous small-angle X-ray scattering (ASAXS). The ASAXS results reveal that the local concentration of the divalent counter-ions in the vicinity of the polymer chains significantly exceeds that of the monovalent counter-ions.     

Exploring Microfluidic Routes to Microgels of Biological Polymers

Polymer microgels in the size range from several micrometers to hundreds of micrometers are used in the pharmaceutical, cosmetics, nutrition, pesticide, and food industries, as well as in the encapsulation of cells. To date, a broad range of strategies for the generation of polymer microgels exist, however, these methods involve multistage processes, do not utilize biocompatible components or do not allow precise control of the dimensions and internal structure of the microgels. Recently, microfluidic strategies for the production of polymer particles have offered precise control over the shapes, morphologies, and size distributions of polymer colloids. This paper discusses the most recent results obtained by the authors in the area of the microfluidic production of biopolymer microgels. It provides a brief review of the microfluidic methods for the continuous synthesis and fabrication of microgels, sets the criteria for the successful microfluidic generation of biomicrogels, and describes two methods for the preparation of microgels by microfluidic means. The article concludes with a summary and an outlook.

     

Direct Organocatalytic Polymerization from Cellulose Fibers

Summary: We have developed the first direct, organocatalytic, bulk ring‐opening polymerization (ROP) of ε‐caprolactone (ε‐CL) with solid cotton and paper cellulose as the initiators. The mild ROPs were performed without solvent, and are operationally simple, inexpensive and environmentally benign. Organic‐acid‐catalyzed heterogeneous derivatization of cellulose provides a novel route to valuable cellulose‐based biocompatible nanomaterials. The furnished polymerization products were characterized by FTIR, ¹H and ¹³C NMR spectroscopy, MALDI‐TOF mass spectrometry and electron microscopy.

Organic acid‐catalyzed ring‐opening polymerization from cellulose fiber.     

Evolution and Operating Experiences with Different Drop‐On‐Demand Systems

Summary: We describe the development of different drop‐on‐demand systems particularly for applications for the liquid handling of biopolymers. Different designs of drop‐on‐demand systems developed by the authors are described. Experiments with these systems show the applicability for pipetting different liquids with different properties. Commercially available systems are also tested. A comparison of the different approaches leads to a discussion of the best fields of application of the different approaches or, alternatively, to the potential further development of the drop‐on‐demand technologies.

Principle setup of the print heads.     

Salt effects on macrophase separations in non‐stoichiometric mixtures of oppositely charged macromolecules: Theory and experiment

In the field of biological applications, polyelectrolyte complexes are proposed to encapsulate bioactive compounds, to deliver drugs, and also to transfect genes into cells under the name of polyplexes. Complex formation is obtained by addition of a polycation solution into a polyanion solution or vice‐versa. This work proposes a theoretical approach to describe complex formation in the case of non‐stoichiometric mixtures of oppositely charged macroions having different degrees of ionization and different degrees of polymerization under different salt conditions. In a second part, comparison was made with experimental data collected when a weak polybase, namely poly(l ‐lysine) under its bromide form was added stepwise to solutions of various polyanions under their sodium salt form, namely poly(l ‐lysine citramide imide), poly(l ‐lysine citramide), and poly(β‐malic acid), the latter lacking hydroxyl groups attached to the main chain. The stability of stroichiometric complexes made of poly(l ‐lysine) and poly(l ‐lysine citramide) having different molecular masses is discussed. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1717–1730     

A facile method to synthesize high‐molecular‐weight biobased polyesters from 2,5‐furandicarboxylic acid and long‐chain diols

In this study, biobased furan dicarboxylate polyesters have been prepared using 2,5‐furandicarboxylic acid (FDCA) and diols with high number of methylene groups (long‐chain diols), namely, 8, 9, 10, and 12. Because of the high boiling points of these diols, a modified procedure of the well‐known melt polycondensation was applied in this work. According to this, the dimethyl ester of FDCA (DMFD) reacted in the first transesterification stage with the corresponding diols forming bis‐hydroxy‐alkylene furan dicarboxylates (BHFD). In the second stage, the BHFD reacted with DMFD again at temperatures of 150–170 °C (for 4–5 h), and in the final stage, the temperature was raised to 210–230 °C (vacuum was applied for 2–3 h). The molecular weight of the polyesters and the content of oligomers, as was verified by gel permeation chromatography analysis, depend on the polycondensation time and temperature. The chemical structure of the polyesters was verified from ¹H NMR spectroscopy. All the polymers were found to be semicrystalline, with melting temperatures from 69 to 140 °C depending on the diol used. In addition, the mechanical properties also varied with the type of diol. The higher values were observed for poly(octylene 2,5‐furanoate), whereas the lowest values were observed for poly(dodecylene 2,5‐furanoate) with the higher number of methylene groups in its repeating unit. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2617–2632