Poly(2-cyclopropyl-2-oxazoline): from rate acceleration by Cyclopropyl to Thermoresponsive properties

The synthesis and microwave-assisted living cationic ring-opening polymerization of 2-cyclopropyl-2-oxazoline is reported revealing the fastest polymerization for an aliphatic substituted 2-oxazoline to date, which is ascribed to the electron withdrawing effect of the cyclopropyl group. The poly(2-cyclopropyl-2-oxazoline) (pCPropOx) represents an alternative thermo-responsive poly(2-oxazoline) with a reversible critical temperature close to body temperature. The cloud point (CP) of the obtained pCPropOx in aqueous solution was evaluated in detail by turbidimetry, dynamic light scattering (DLS) and viscosity measurements. pCPropOx is amorphous with a significantly higher glass transition temperature (T(g) similar to 80 degrees C) compared to the amorphous poly(2-n-propyl-2-oxazoline) (pnPropOx) (T(g) similar to 40 degrees C), while poly(2-isopropyl-2-oxazoline) piPropOx is semicrystalline. In addition, a pCPropOx comb polymer was prepared by methacrylic acid end-capping of the living cationic species followed by RAFT polymerization of the macromonomer. The polymer architecture does not influence the concentration dependence of the CP, however, both the CP and T(g) of the comb polymer are lower due to the increased number of hydrophobic end groups

Metallo-Supramolecular Complexation Behavior of Terpyridine- and Ferrocene-Based Polymers in Solution—A Molecular Hydrodynamics Perspective

The contribution deals with the synthesis of the poly(methacrylate)-based copolymers, which contain ferrocene and/or terpyridine moieties in the side chains, and the subsequent analysis of their self-assembly behavior upon supramolecular/coordination interactions with Eu 3+ and Pd 2+ ions in dilute solutions. Both metal ions provoke intra and inter molecular complexation that results in the formation of large supra-macromolecular assembles of different conformation/shapes. By applying complementary analytical approaches (i.e., sedimentation-diffusion analysis in the analytical ultracentrifuge, dynamic light scattering, viscosity and density measurements, morphology studies by electron microscopy), a map of possible conformational states/shapes was drawn and the corresponding fundamental hydrodynamic and macromolecular characteristics of metallo-supramolecular assemblies at various ligand-to-ion molar concentration ratios ( M / L ) in extremely dilute polymer solutions ( c [ η ] ≈ 0.006 ) were determined. It was shown that intramolecular complexation is already detected at ( L ≈ 0.1 ), while at M / L > 0.5 solution/suspension precipitates. Extreme aggregation/agglomeration behavior of such dilute polymer solutions at relatively “high” metal ion content is explained from the perspective of polymer-solvent and charge interactions that will accompany the intramolecular complexation due to the coordination interactions

Hydrodynamic Characteristics and Conformational Parameters of Ferrocene-Terpyridine-Based Polymers

Nowadays, the study of metallopolymers is one of the fastest growing areas of polymer science. Metallopolymers have great potential for application in multiple technological and various biomedical processes. The macromolecules with the possibility of varying the number and type of metal ions along the entire length of the polymer chain are of particular interest. In this regard, this study presents results on two successfully synthesized homopolymers, random and block copolymers based on PMMA, containing ferrocene and terpyridine moieties in the side chain. Different architectures of copolymers may attribute interesting properties when creating complexes with various metal ions. A detailed hydrodynamic study of these structures was carried out, the consistency of hydrodynamic data was established using the concept of a hydrodynamic invariant, the absolute values of the molar masses of the studied objects were calculated, and the conformational parameters of macromolecules were determined. Using the Fixman–Stockmayer theory, the equilibrium rigidities of the studied systems were calculated and the relationship between the chemical structure and conformational characteristics was established. The studied copolymers can be attributed to the class of flexible-chain macromolecules. An increase in the equilibrium rigidity value with an increase of the side chain, which is characteristic of comb-shaped polymers, was determined

Hydrodynamic analysis of macromolecular and colloidal systems by analytical ultracentrifugation and related methods

In the last decades, the studies in the field of macromolecular chemistry resulted in the appearance of numerous different polymeric and colloidal systems, which are capable for the intra and inter molecular complexation. One of the main goals of polymer characterization is to be able to predict certain physical/chemical properties of the macromolecules based on their conformational characteristics. The accuracy of the estimation of the molecular and conformational characteristics increases with the simultaneous study and comparison of the data obtained by different hydrodynamic methods. The main scope of the current thesis is investigation of complex macromolecular and colloidal systems by the methods of molecular hydrodynamics, in particular, analytical ultracentrifugation, intrinsic viscosity and translation diffusion

Towards DNA sensing polymers: interaction between acrylamide/3-(N,N-dimethylaminopropyl)-acrylamide and DNA phage λ at various N/P ratios

The present study strongly relates to ongoing research on the development of cationic polymers which are of great interest due to their enormous potential for biomedical applications, especially as non-viral vectors for gene therapy, antimicrobial agents and active components in DNA sensing devices. The current paper demonstrates that a functional group approach can be successfully realized in a free-radical copolymerization process to prepare cationic copolymers with a desired composition of amine groups, which can be protonated in water thus, providing electrostatic interactions between a polycation and DNA. Three replicas of the cationic copolymer, acrylamide/3-(N,N-dimethylaminopropyl)-acrylamide (AADMAPA), were synthesized using this strategy. The values of average molecular mass and polydispersity index, are similar for the replicas, averaged to 24 000 2000 g mol1 and 1.5 0.1, respectively. The copolymer composition according to 1 H-NMR (D2O), was corresponded to the molar ratio of initial monomers. The dynamic light scattering studies and zeta potential measurements confirmed that in water positively charged AADMAPA/DNA polyplexes are formed at N/P > 2.2: the formed particles have bimodal distributions with the average diameters of 70 and 700 nm. Zeta potential measurements indicated that the point of zero charge (isoelectric point) is close to N/P y 2.2. According to the atomic force microscopy positively charged AADMAPA/DNA polyplexes have axially symmetric shapes.The authors are grateful to Prof. Babushkina T. A., Mrs Klimova T. P. for helpful discussion and NMR spectral data. The authors also acknowledge Mrs Klemenkova Z. S. for IR spectral data. E. Laukhina acknowledges the support from Instituto de Salud Carlos III, through “Acciones CIBER”. The Networking Research Center on Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), an initiative funded by the VI National R&D&I Plan 2008-2011, Iniciativa Ingenio 2010.Peer reviewe

Unexpected radical polymerization behavior of oligo(2-ethyl-2-oxazoline) macromonomers

A well-defined oligo(2-ethyl-2-oxazoline)acrylate (OEtOxA) macromonomer was obtained by direct end functionalization of the living cationic oxazolinium species from the cationic ring-opening polymerization of EtOx with in situ deprotonated acrylic acid. Kinetic studies during subsequent reversible addition-fragmentation chain transfer (RAFT) polymerization as well as nitroxide mediated polymerization (NMP) experiments revealed proceeding monomer consumption but no increase of the molar mass of the resulting comb polymers. The chain transfer during the radical polymerizations is proposed to result from backbiting and subsequent beta-scission of the formed mid-chain radical and took place in a well-defined manner, so that POEtOxA could also be obtained by free radical polymerization with a PDI value below 1.2. A series of POEtOxA was synthesized by RAFT polymerization with varying [monomer]/[chain transfer agent] (M/CTA) ratios and analyzed in detail by means of analytical ultracentrifugation and small angle neutron scattering, indicating that the backbone DP does not exceed 25, which is in accordance with the thermal polymer properties in bulk and in aqueous solution (T-g = 32 degrees C, T-cp approximate to 73 degrees C)