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

Functionalization of polyacrylamide for nanotrapping positively charged biomolecules

Engineering new materials which are capable of trapping biomolecules in nanoscale quantities, is crucial in order to achieve earlier diagnostics in different diseases. This article demonstrates that using free radical copolymerization, polyacrylamide can be successfully functionalized with specific synthons for nanotrapping positively charged molecules, such as numerous proteins, through electrostatic interactions due to their negative charge. Specifically, two functional random copolymers, acrylamide/acrylic acid (1) and acrylamide/acrylic acid/N-(pyridin-4-yl-methyl)acrylamide (2), whose negative net charges differ in their water solutions, were synthetized and their ability to trap positively charged proteins was studied using myoglobin as a proof-of-concept example. In aqueous solutions, copolymer 1, whose net charge for a 100 chain fragment (QpH 6/M) is −1.323 × 10−3, interacted with myoglobin forming a stable monodisperse nanosuspension. In contrast, copolymer 2, whose value of QpH 6/M equals −0.361 × 10−3, was not able to form stable particles with myoglobin. Nevertheless, thin films of both copolymers were grown using a dewetting process, which exhibited nanoscale cavities capable of trapping different amounts of myoglobin, as demonstrated by bimodal AFM imaging. The simple procedures used to build protein traps make this engineering approach promising for the development of new materials for biomedical applications where trapping biomolecules is required.Peer reviewe

Hyperbranched Poly(ethylene glycol) Copolymers: Absolute Values of the Molar Mass, Properties in Dilute Solution, and Hydrodynamic Homology

Hyperbranched poly­(ethylene glycol) copolymers were synthesized by random anionic ring-opening multibranching copolymerization of ethylene oxide with glycidol as a branching agent, leading to poly­(ethylene glycol) structure with glycerol branching points. Extending the available range of molar masses by novel synthesis strategies, a limited extent of control over the degree of polymerization was achieved by variation of the solvent in this copolymerization. Generally, absolute molar mass characterization of hyperbranched polymers still represents an unresolved challenge. A series of the hyperbranched poly­(ethylene glycol)-<i>co</i>-(glycerol) copolymers (<i>hb</i>PEGs) of a wide range of molar masses (1400 < <i>M</i> < 1 700 000 g mol^–1), degree of branching (DB) = 0.04–0.54, and moderate polydispersity (<i>M</i>_w/<i>M</i>_n) ≈ 2.1 ± 0.2 were studied, in both water and dimethylformamide by the methods of molecular hydrodynamics. Analytical ultracentrifugation, intrinsic viscosity, translational diffusion measurements, and SEC were combined. Molar masses of <i>hb</i>PEGs were estimated from the comparison of the velocity sedimentation and translational diffusion coefficients, i.e., applying the Svedberg relationship. It was demonstrated that the use of linear PEG for the SEC calibration results in the significantly underestimated values of the molar masses of <i>hb</i>PEGs. The largest <i>hb</i>PEG samples exhibited a hydrodynamic radius of ≈14 nm in aqueous solution. The obtained Kuhn–Mark–Houwink–Sakurada scaling relations show linear trends in all range of molar masses. The detected scaling indexes virtually correspond to the homologous series characterized by a direct proportionality between the molar mass and the volume of the macromolecules that make up this series. The effect of branching on the molecular dimensions and on the hydrodynamic characteristics is discussed, and the corresponding contraction factors have been estimated

Polyelectrolyte Complexes of DNA and Linear PEI: Formation, Composition and Properties

In the present study, the complexation between linear 13.4 kDa poly­(ethylene imine) (LPEI) and plasmid DNA was investigated. Analytical ultracentrifugation (AUC) was used for size and molar mass determination. Additionally, the morphology was studied by scanning force microscopy. The polyplex formation was investigated in a wide range of PEI nitrogen to DNA phosphate ratios (N/P). At N/P ratios below 1, the PEI/DNA complex formation is characterized by an incomplete DNA condensation and the formation of the primary DNA/PEI complexes. The merging of the initially formed polyplexes occurs at N/P ∼2, resulting in the formation of polyplexes with much larger size and high aggregation rate. Stable and uniform polyplexes were formed at N/P > 10, with average sizes of the polyplexes of about 170 ± 65 nm. The content of uncomplexed PEI chains in the polyplex dispersion was estimated at four different N/P ratios, 6.2, 11.6, 28.6, and 57.8, by combining preparative centrifugation with a copper complex assay and by sedimentation velocity analysis as an alternative method. It is demonstrated that virtually all added PEI binds to the DNA at N/P < 2.5; further addition of PEI results in the appearance of a large amount of free PEI in solution. Nevertheless, PEI is able to bind in the whole range of N/P ratios tested. According to the data collected by sedimentation velocity analysis and scanning force microscopy, the single PEI/DNA complexes are composed on average of 8 to 32 single condensed DNA plasmids and 70 ± 25 PEI molecules