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Surface pressure versus mean molecular area isotherms of Langmuir films of a hybrid diblock copolymer of poly(ethylene glycol) (PEG) and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS) together with Brewster angle microscopy reveal details of the phase transitions. The formation of a periodic wrinkling pattern in collapsed films is observed by epifluorescence microscopy after applying several compression-expansion cycles above the surface pressure of ≈18 mN/m. The wrinkle formation is reversible upon compression and expansion of the Langmuir films. Two distinct orientations of POSS molecules are assumed in Langmuir films upon compression, vertically for chains close to the water surface and horizontally orientated upper layers with significant amounts of PEG in between them. Thus, the wrinkling forms mainly in the top stiffer MA-POSS blocks above a certain compressional stress. The wrinkles disappear during the Langmuir-Blodgett (LB) transfer. Nevertheless, atomic force microscopy and grazing incidence wide-angle X-ray scattering experiments reveal the formation of highly ordered POSS molecules in LB films.

A novel strategy for the formation, without the need for organic solvents, of stable giant proteopolymersomes from the highly water-soluble triblock copolymer poly(2,3-dihydroxypropyl methacrylate)...

Carbonyl-centered hydrogen bonds with various strength and geometries are often exploited in materials to embed dynamic and adaptive properties, with the use of thiocarbonyl groups as hydrogen-bonding acceptors remaining only scarcely investigated. We herein report a comparative study of C2=O and C2=S barbiturates in view of their differing hydrogen bonds, using the 5,5-disubstituted barbiturateBand the thiobarbiturateTBas model compounds. Owing to the different hydrogen-bonding strength and geometries of C2=O vs. C2=S, we postulate the formation of different hydrogen-bonding patterns in C2=S in comparison to the C2=O in conventional barbiturates. To study differences in their association in solution, we conducted concentration- and temperature-dependent NMR experiments to compare their association constants, Gibbs free energy of association∆Gassn., and the coalescence behavior of the N-H‧‧‧S=C bonded assemblies. In Langmuir films, the introduction of C2=S suppressed 2D crystallization when comparingBandTBusing Brewster angle microscopy, also revealing a significant deviation in morphology. When embedded into a hydrophobic polymer such as polyisobutylene, a largely different rheological behavior was observed for the barbiturate-bearingPBcompared to the thiobarbiturate-bearingPTBpolymers, indicative of a stronger hydrogen bonding in the thioanaloguePTB. We therefore prove that H-bonds, when affixed to a polymer, here the thiobarbiturate moieties inPTB,can reinforce the nonpolar PIB matrix even better, thus indicating the formation of stronger H-bonds among the thiobarbiturates in polymers in contrast to the effects observed in solution.

Protein-polymer conjugates have been employed as therapeutics since they exhibit frequently higher stability, prolonged in vivo half-life, and lower immunogenicity compared to native proteins. The first part of this report describes the enzymatic synthesis of poly(glycerol adipate) (PGA(M)) by transesterification between glycerol and dimethyl adipate using lipase B from Candida antarctica (CAL-B). PGA(M) is a hydrophilic, biodegradable but water insoluble polyester. By acylation, PGA(M) is modified with 6-(Fmoc-amino)hexanoic acid and with hydrophilic poly(ethylene glycol) side chains (mPEG12) rendering the polymer highly water soluble. This is followed by the removal of protecting groups, fluorenylmethyloxycarbonyl (Fmoc), to generate polyester with primary amine groups, namely PGA(M)-g-NH2-g-mPEG12. 1H NMR spectroscopy, FTIR spectroscopy, and GPC have been used to determine the chemical structure and polydispersity index of PGA(M) before and after modification. In the second part, we discuss the microbial transglutaminase (mTGase)-mediated conjugation of the model protein dimethylcasein (DMC) with PGA(M)-g-NH2-g-mPEG12 under mild reaction conditions. SDS-PAGE proves the protein-polyester conjugation.

The odd–even effect of a homologous series of two poly(ethylene oxide) chains separated by (CH2)n spacers and joined by two 1,2,3-triazole rings with 2 ≤ n ≤ 8 (PEO11-TR-(CH2)n-TR-PEO11) is reporte...

The Langmuir film formation of poly(ethylene glycol) (PEG)- and poly(methacrylo polyhedral oligomeric silsesquioxane) P(MA-POSS)-based diblock copolymers (PEG5k-b-P(MA-POSS)x) at the air/water interface is investigated. While the Langmuir film formed by the PEG5k collapses at π ≈ 8 mN m−1, the PEG5k-b-P(MA-POSS)x forms a stable film on the water surface revealing various phase transitions in surface pressure vs mean molecular area (π-mmA) isotherm—manifested by various pseudo-plateaus during compression. At higher surface coverage, the π-mmA isotherm exhibits a phase transition that is attributed to the transformation of the P(MA-POSS) monolayer into a multilayer film that is confirmed by AFM measurements of the Langmuir-Blodgett films fabricated before and after the phase transition and direct infrared reflection absorption spectroscopy of the Langmuir film during compression. At a still higher surface pressure, another pseudo-plateau is observed that is assigned to the ultimate film collapse as verified by the Brewster angle microscopy.

The studies of phase behavior, dielectric relaxation, and other properties of poly(ethylene oxide) (PEO)/poly(methyl acrylate) (PMA) blends with the addition of lithium perchlorate (LiClO4) were done for different blend compositions. Samples were prepared by a solution casting technique. The binary PEO/PMA blends exhibit a single and compositional-dependent glass transition temperature (Tg), which is also true for ternary mixtures of PEO/PMA/LiClO4 when PEO was in excess with low content of salt. These may indicate miscibility of the constituents for the molten systems and amorphous domains of the systems at room temperature from the macroscopic point of view. Subsequently, the morphology of PEO/PMA blends with or without salt are correlated to the phase behavior of the systems. Phase morphology and molecular interaction of polymer chains by salt ions of the systems may rule the dielectric or electric relaxation at room temperature, which was estimated using electrochemical impedance spectroscopy (EIS). The frequency-dependent impedance spectra are of interest for the elucidation of polarization and relaxation of the charged entities for the systems. Relaxation can be noted only when a sufficient amount of salt is added into the systems.

We present first results on triazolium-based ionic liquids (ILs) as a novel class of nonderivatizing solvents for cellulose. Despite their chemical similarity to imidazolium cations, the 1,2,3-triazolium cation lacks the isolated ring proton, leading to reduced formation of N-heterocyclic carbenes (NHCs) and therefore to lower reactivity and less unwanted side reactions. We synthesized six ILs based on 1,2,3-triazolium and 1,2,4-triazolium cations. The acetates are room-temperature ionic liquids and dissolve a similar amount of cellulose as the corresponding imidazolium salt. From NMR spectroscopy of the solution, we rule out polymer degradation. The cellulose solubility rises with increasing anion basicity, while being almost independent of the cation. We perform molecular dynamics simulations and compute enthalpies of solvation, which quantitatively fit the experimental solubilities. Trajectory analysis reveals strong hydrogen bonds between acetate anions and cellulose hydroxyl groups, while the cations do not form strong hydrogen bonds with cellulose. Thus, the simulations provide an atomistic explanation of our experimental observations.

We synthesized poly(ethylene glycol) (PEG) networks by Cu(I) catalyzed azide-alkyne cycloaddition (CuAAC) using three-arm star-PEG with azide end groups and linear PEG oligomers of different molar masses with alkyne end groups. After extensive characterization of the networks by 13C MAS and 1H multiple-quantum (MQ) NMR spectroscopy, their crystallization behavior is studied by differential scanning calorimetry (DSC), temperature dependent small and wide angle X-ray scattering (SAXS, WAXS) as well as 1H FID NMR. Since CuAAC introduces 1,4-disubstituted 1,2,3-triazole (TR) rings as chain defects into the network, we compare our results with those obtained from linear PEG which contained a purposely introduced TR ring in the middle of the polymer chain. PEG network chains are able to form the characteristic 72 helices upon cooling to −20 °C and crystallize into the monoclinic unit cell in complete analogy to the homopolymer. The crystallinity of the networks, though it is lower as compared to the linear samples, reached values of about 30–50%. Given the fact that the network chains are highly constrained in their configurational freedom, this is very surprising. However, cross-links and the TR defects have only a minor effect on the molecular dynamics of the PEG chains in the crystals since the characteristic αc-relaxation process (helix jumps) is also detected in the PEG networks by analysis of the 1H FIDs. The SAXS data reveal that randomly arranged stacks of lamellae are formed upon crystallization and the chains are tilted in the crystals at large angles of about 40°–55°. Supported by all experimental data, we propose a model to explain the formation of polymer crystals in the networks and concluded that primary and secondary loops which extent the network chains beyond the length of the linear precursors play an essential role for the crystallization.

The linear polyester poly(glycerol adipate) (PGA) with its free pendant hydroxyl groups was covalently grafted with indomethacin which yields polymeric prodrugs. It was possible to produce nanospheres with narrow particle size distribution of these polymer-drug conjugates with an optimized interfacial deposition method. Nanospheres were characterized by zeta potential measurements, dynamic light scattering, electron microscopy and nanoparticle tracking analysis. Moreover, cell viability studies and cytotoxicity tests in three different cell lines were carried out showing low toxicity for three different degrees of grafting. In addition, the nanospheres had (in contrast to the free drug) low hemolytic activity in vitro. Release studies of nanodispersions are challenging. The use of a specially developed setup with highly porous aluminum oxide membranes enabled us to overcome problems associated with other setups (e.g. dialysis membranes). A slow and controlled release profile without any burst was observed over 15 days. The results indicate that indomethacin-PGA conjugates can be formulated successfully as nanospheres with the desired characteristics of small size with narrow distribution, controlled drug release and low toxicity. The newly developed particles have the potential to improve the therapy of inflammation and associated diseases.

We have used Cu(I)-catalyzed azide–alkyne cycloaddition to synthesize a new series of poly(ethylene oxide)s having in the center of their chains two 1,2,3-triazole (TR) rings separated by (CH2)n spacers with 2 ≤ n ≤ 4 (PEO11-TR-(CH2)n-TR-PEO11). The degree of crystallinity obtained by temperature-dependent WAXS measurements indicates that only one out of the two PEO11 chains of the three polymers forms a 72 helix upon cooling to −10 °C and crystallizes into a monoclinic unit cell known from PEO homopolymer. A solid-state phase transition occurs for all samples during heating below their melting temperature. Solid-state 13C MAS cross-polarization and single-pulse NMR spectroscopy indicate the complete incorporation of the chain defects into the PEO crystals (PEO-TR phase) during this transition. The 2D WAXS pattern of an oriented PEO11-TR-(CH2)2-TR-PEO11 sample generates a structural model where the crystal lattice of the initial PEO phase becomes highly distorted during the solid-state phase transition du...

A polyphosphoester (PPE) with phenyl phosphate groups separated by precisely 20 CH2 groups in its backbone was dissolved in chloroform and spread on the water surface of a Langmuir trough. The surface pressure vs area per monomer unit (π-A) Langmuir isotherm together with epifluorescence and Brewster angle microscopy suggested that some crystallization occurred already at zero surface pressure immediately after solvent evaporation of the spread polymer solution. The extended plateau region of the Langmuir isotherm in the range of π ≈ 4.5 mN m−1 corresponds to the 2D crystallization of most polymer chains. Brewster angle and epifluorescence microscopy show that during the crystallization of PPE in the Langmuir film single crystal like hexagonal entities are formed with lateral dimensions of up to 20 µm. These entities break upon compression beyond the limiting area per monomer unit which leads to a decrease of the elasticity modulus of the Langmuir film. The morphology of the single crystals and their failure upon compression are also observed in Langmuir-Blodgett films by atomic force microscopy. The thickness of the crystals is about 2.5 nm at the end of the plateau range and reaches 3.0 nm upon further compression. The polymer crystallization on the water surface is also confirmed by infrared reflection absorption spectroscopy.

Fluorocarbon amphiphiles are anthropogenic substances widely used in diverse applications such as food packaging, clothing or cookware. Due to their widespread use and non-biodegradability, these chemicals are now ubiquitous in the natural world with high propensity to bioaccumulate in biological membranes, wherein they may affect microscopic properties. Here, we test the hypothesis that a typical fluorocarbon amphiphile can affect lipid membranes similarly to cholesterol by investigating the effect of 1H,1H,2H,2H-perfluoro-1-decanol (8:2 FTOH) on 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes. Using solid-state nuclear magnetic resonance spectroscopy, differential scanning calorimetry and confocal microscopy, we present a consistent set of independent experimental evidences supporting this hypothesis, namely that upon incorporation of 8:2 FTOH, (i) a condensing effect on the acyl chains occurs in the fluid phase, (ii) coexistence of two membrane phases is observed below melting, and (iii) the melting temperature of DPPC varies no more than approximately ±1 °C up to a concentration of 40 mol% of 8:2 FTOH. The condensing effect is quantified by means of advanced dipolar recoupling solid-state NMR experiments and is found to be of approximately half the magnitude of the cholesterol effect at the same concentration.

The phase behavior of binary mixtures of non-crystallizable racemic poly ( d , l -lactic acid) (PDLLA) and the mosquito-repellent/drug N,N-diethyl-3-methylbenzamide (DEET) was analyzed with respect to the effect of the polymer molar mass on the liquid-liquid (L–L) phase separation characteristics, by cloud-point measurements and differential scanning calorimetry. The PDLLA/DEET system shows a subambient upper critical solution temperature (UCST), with the critical temperature decreasing and critical polymer concentration increasing with decreasing molar mass of PDLLA. The obtained L–L phase separation curves were used to estimate the temperature-dependence of the interaction parameter, confirming that the enhanced miscibility of the system components in case of low molar mass PDLLA is due to increased entropy of mixing.

Many text books and publications do not focus on the necessity of chain tilting in crystalline lamellae of oligomers and polymers, a fundamental aspect of their crystallization already discussed by Flory. Herein we investigate the chain tilt of ethylene oxide oligomers (EOs) containing various midchain defects by WAXS, SAXS and solid state 13C MAS NMR spectroscopy. At low temperatures, one out of the two EO chains of EO9-meta-EO9 and EO11-TR-EO11 containing a 1,3-disubstituted benzene or a 1,4-disubstituted 1,2,3-triazole defect in central position of the oligomer chain forms crystals and the other EO chain as well as the defect remain in the amorphous phase. The aromatic midchain defect of these two oligomers can be incorporated into the crystalline lamella upon heating below Tm. Then, the adjoining amorphous EO chain crosses from the lamellae to the amorphous regions at an angle ξ, which is preordained by the substitution pattern of the aromatic defect, revealing that the chain tilt angle ranges between...

Poly(ethylene oxide) (PEO) based electrolytes are of great importance for applications in electrochemical devices. Since their ion conductivity is severely hampered by crystallization, several approaches are carried out to enhance the low temperature ion conductivity of PEO such as the addition of polar solvents or the synthesis of more complex polymer architectures. In this study, solvent-like defects are introduced in the center of the PEO chain to reduce its crystallinity with the aim to enhance ion conductivity. The ion conductivities of four polymer electrolytes, containing either a 1,4-disubstituted 1,2,3-triazole (TR) or ortho-, meta- or para-disubstituted benzene defects are measured by impedance spectroscopy after addition of lithium perchlorate (LiClO4, EO:Li = 50:1) to the polymer. The TR containing sample shows a 15 to 700 times higher ion conductivity at T = − 10 °C as compared to the benzene containing PEOs with different substitution pattern. This can be explained by the lower glass transition temperature of the TR containing electrolytes compared to the benzene containing electrolytes. Furthermore, the dependence of the ion conductivity on the LiClO4 concentration in the melt at T = 70 °C is studied for TR containing electrolytes and compared to the respective defect free PEO22 electrolytes. The electrolytes with the TR defect have higher conductivities in the concentration range (50:1 ≥ EO:Li ≥ 8:1) compared to the uninterrupted PEO22 revealing that the incorporation of a solvent-like defect with high dielectric constant into a PEO chain is an effective strategy to enhance the ion conductivity of PEO electrolytes. This is also supported by 7Li NMR spectroscopy showing that LiClO4 is soluble 1,2,3-triazole but insoluble in benzene. Additionally, 1,2,3-triazoles can also coordinate Li+-ions and, thus, actively contribute to the transport of the Li+-ions.

The fluorophilicity of fluorinated rhodamine-based fluorescence dyes (F-rhodamines) functionalized with CH 2 -C 3 F 7 (Rh-CH 2 -C 3 F 7 ) or C 2 H 4 -C 10 F 21 (Rh-C 2 H 4 -C 10 F 21 ) at both amine groups was tested in mixed monolayers of stearic acid (SA) and perfluorostearic acid (FC18) on a Langmuir trough coupled with epifluorescence microscopy. The composition of the Langmuir monolayers was systematically changed from 100% FC18 to 100% SA in order to investigate the fluorophilicity and lipophilicity of the two F-rhodamines by observing their partitioning behavior within the different monolayers. The F-rhodamine bearing the longer perfluoroalkyl group and alkyl spacer (Rh-C 2 H 4 -C 10 F 21 ) showed a substantially higher affinity to the FC18 rich phases in contrast to the F-rhodamine having the shorter perfluoroalkyl chain and alkyl spacer (Rh-CH 2 -C 3 F 7 ) which was excluded from FC18 as well as from SA domains. The FC18, SA, and FC18/SA 50:50 (mol%) monolayers were further investigated by infrared reflection absorption spectroscopy (IRRAS) in order to investigate the phase behavior of FC18 and SA. It was observed that the orientations of FC18 and SA molecules in the pure and mixed monolayers do not change upon compression. Furthermore, a decrease in the order of the FC18 molecules in the mixed monolayer is observed upon the addition of SA. The opposite is not valid in a sense that no loss in order of the SA molecules was observed upon the addition of FC18. This shows that SA partitions more into FC18 phases than FC18 into SA domains. This is due to the weaker van der Waals forces present between the perfluoroalkyl chains in comparison with stronger ones existing between the alkyl chains.

Poly(glycerol adipate) (PGA) was synthesized by enzymatic polymerization and grafted with different amounts of oleoyl chloride. A series of graft copolymers PGA-g-Ox was obtained where O represents the oleate side chains and x is the degree of grafting (mol% of the pendant OH groups of PGA esterified) ranging from 11 to 90. Small angle X-ray scattering (SAXS) data revealed nanophase separation of the oleate side chains into nanodomains in bulk and wide angle X-ray scattering (WAXS) profiles showed a broad halo, reflecting the amorphous nature of the synthesized graft polymers. Glycerol monooleate (GMO), an amphiphilic lipid with one hydrophobic oleate tail and a glycerol hydrophilic head group, self-assembles into various liquid crystalline phases in the presence of water. Since oleate chains are integral part of both GMO and the graft copolymers, a certain degree of miscibility can be expected influencing the self-assembly behavior. Using SAXS for phase identification, systematic studies were carried out at room temperature on the ternary system of GMO/PGA-g-O22/water and the ternary phase diagram was constructed. The addition of polymer did influence the phase behavior of the GMO/water system. The water in the lamellar and cubic mesophases was partially replaced by PGA-g-O22. Furthermore, keeping the GMO/water ratio constant at 1:1, the addition of PGA-g-O22 lead to swelling of the water channels in the inverse bicontinuous Pn3m cubic phase. Preliminary investigations on the potential application of PGA-g-O22 as a stabilizer of structured nanoparticles in aqueous dispersions were carried out employing different transmission electron microscopy techniques.

Helical jumps in poly(ethylene oxide), which are the molecular processes underlying the intracrystalline chain diffusion, are studied on the microseconds to milliseconds time scale by means of NMR. Using a simple proton time-domain technique, a wide range of melt-crystallized morphologies is investigated ranging from extended-chain crystals of short chains to crystals with disordered fold surfaces of longer chains up to 190 kg/mol. From variable-temperature data we directly determine the Arrhenius activation parameters and find that the activation energy is always around 65 kJ/mol. At a given temperature, average correlation times vary from sample to sample over about 1 decade and increase approximately linearly with the lamellar thickness. The observed linear relation is reproduced by a generic Monte Carlo simulation model implementing a mechanism of diffusing defects. The experimental results are compared to 1D carbon-13 MAS exchange NMR (CODEX) and proton rotating-frame relaxation (R1ρ) data, for which...

The monolayer behavior of a l- DPPC derivative with a single fluorination in one of its terminal methyl groups (F-DPPC) at air-water interface was investigated by epifluorescence microscopy and infrared reflection absorption spectroscopy (IRRAS). Epifluorescence microscopy was utilized to study the shape and morphology of liquid-condensed (LC) domains observed upon compression of the film. IRRAS was employed for the determination of chain order and orientation. The shapes of LC-domains in a monolayer of F-DPPC are more dependent on the rate of compression than those of DPPC. The LC domains of F-DPPC display pronounced fractal growth patterns depending on the compression speed. The evolution of LC domain occurs under dominating electrostatic dipolar forces in F-DPPC. IRRAS measurements with the analysis of the frequency of the methylene stretching vibrations as a function of film compression show that the acyl chains in an F-DPPC monolayer in the LE-phase are more disordered than those in a DPPC film. The reason for the higher chain disorder in LE phase F-DPPC monolayers is a back folding of the fluorinated sn-2 chain terminus towards the air-water interface leading to larger molecular area requirement. Angular dependent IRRA spectra of monolayers at a surface pressure of 30 mN m−1 show that in the LC phase DPPC and F-DPPC exhibit a similar tilt of the acyl chains of ca. 28−30 ° relative to the surface normal. F-DPPC is ideally miscible with l -DPPC-d62 having the same chirality, as indicated by epifluorescence images and by IRRAS. However, the LC domains in an equimolar mixture of d -DPPC and F-DPPC having opposite chirality show multi-lobed complex domain patterns indicating chiral phase separation within LC domains.

Enzymatic polymerization is an environmentally benign process for the synthesis of biodegradable and biocompatible polymers. The regioselectivity of lipase B from Candida Antarctica (CAL-B) produces linear functional polyesters without protection-deprotection steps. In this work, two different methods for the enzymatic synthesis of functional polyesters based on renewable resources, as, e.g., glycerol, using CAL-B are outlined. Poly(glycerol adipate) was synthesized by enzymatic transesterification between glycerol and divinyl adipate or dimethyl adipate. Methods are also reported to graft poly(glycerol adipate) with different amounts of hydrophobic side chains (lauric, stearic, behenic, and oleic acids) and hydrophilic poly(ethylene glycol) side chains, respectively. The hydrophilicity or lipophilicity of grafted polyesters is well controlled by changing the degree of grafting of hydrophilic and hydrophobic side chains. The multiple grafted polyesters are characterized by NMR spectroscopy, differential scanning calorimetry, gel permeation chromatography, and X-ray diffraction. Furthermore, the self-assembly of the graft copolymers in water and their use as steric stabilizers for cubosomes are discussed. For this purpose mainly dynamic light scattering and small angle X-ray scattering have been employed.

The 1-octanol/water (ln PO/W) and perfluoro(methylcyclohexane)/toluene (ln PPFMC/Tol) partition coefficients were measured for four fluorinated rhodamine-based fluorescence dyes (F-rhodamines) functionalized with F-ponytails of various lengths CnH2n-CmF2m+1 (n = 1,2 and m = 3,7,8,10) at both amine groups. Here, the ln PO/W accounts usually for the lipophilic-hydrophilic ratio in aqeous (biological) media whereas the ln PPFMC/Tol is a standard value for the description of the fluorophilic-lipophilic ratio. Both partition coefficients correlated with the CmF2m+1/CnH2n ratio, but not directly with the length of the F-ponytails. The ability of the F-rhodamines to incorporate into the hydrophobic part of the bilayer of giant unilamellar vesicles (GUVs) of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) mixed with 1H,1H,2H,2H-perfluoro-1-octanol (F6H2OH) using confocal laser scanning microscopy was tested and the partitioning of the F-rhodamines into the mixed GUVs could not be explained exclusively using the two ln P values mentioned above. Two other partition coefficients between F6H2OH/W (ln PF6H2OH/W) and perfluoro-n-octane/n-octane (ln PF-oct/oct) were measured. The ln PF-oct/oct correlated in a comparable way with the ln PPFMC/Tol, whereas ln PF6H2OH/W accounting for the fluorophilic-hydrophilic ratio correlated with the length of the F-ponytails and additionally clarified the different staining abilities of the synthesized F-rhodamines in the mixed GUVs.

The annular tautomerism of lithium 1,2,3-triazolate (Li-TR) is experimentally investigated in the solid state by X-ray diffraction and in methanolic solution by NMR spectroscopy. DFT-based ab initio molecular dynamics simulations are additionally carried out to characterize the solvation structure of Li-TR in methanol and to determine the free energy landscape of the two tautomers.

Poly(ethylene oxide) (PEO) is a polymer of great interest due to its prevalence in biomedical, pharmaceutical, and ion conductive systems. In this study, the crystallization behaviors of a PEO with 22 monomer units (PEO22) and a PEO having the same degree of polymerization but with an additional 1,4-disubstituted 1,2,3-triazole ring in central position of the chain (PEO11-TR-PEO11) are investigated. PEO11-TR-PEO11 shows one type of lamella crystal after cooling to T = 0 °C, but structural changes during heating below their final melting are detected by WAXS, DSC, POM, and solid-state NMR spectroscopy. The lamella thickness increases, but simultaneously the helix–helix distance decreases and an additional Bragg reflection appears at 2θ = 22.1°. A model is proposed which explains these structural changes by incorporation of the TR ring into the crystals which are additionally stabilized by attractive C–H···π interactions of the TR rings. Additionally, two different types of extended chain lamella crystals a...

Poly(glycerol adipate) is a new biodegradable polyester and a promising alternative to the commonly used PLA and PLGA. The free hydroxyl groups of the PGA backbone allow the conjugation of fatty acids and therefore, enable the synthesis of versatile FA-PGAs with tunable properties. Depending on the fatty acid (i.e. stearic and behenic acid) and the substitution degree, it is possible to adjust the physicochemical properties. Different FA-PGAs were investigated regarding their suitability to form solid microparticles by DSC, contact angle and oscillatory rheology measurements. Dibenzoyl Thiamine (DBT), a lipophilic drug with high potential for the prophylactic treatment of cleft lip and neuroprotective activity, was incorporated in the microparticles. In order to characterize the microparticles, laser diffraction analysis, SEM and XRD measurements were conducted and drug loading, as well as encapsulation efficiency, were determined. In addition, in-vitro release experiments were carried out. Due to the various possibilities to adjust the properties of the polymer, these FA-PGA microparticles have the potential to improve controlled drug delivery and to be a useful alternative to PLA and PLGA.

Poly (e-caprolactone) (PCL) dissolved in chloroform was spread on the water surface of a Langmuir trough and after solvent evaporation, the surface pressure vs area (π-A) Langmuir isotherm was recorded. An extended plateau region indicates a 1st order phase transition related to PCL crystallization as also confirmed by Brewster angle microscopy (BAM). Infrared reflection absorption spectroscopy (IRRAS) and grazing incidence wide angle X-ray scattering (GI-WAXS) reveal details of the PCL crystallization process on a molecular level. The IRRAS and GI-WAXS experiments confirm that crystallization occurs at the plateau region of the π-A Langmuir isotherm. GI-WAXS also confirms that the polymer chains in the crystals are tilted by ≈ 21° with respect to the water surface normal direction. This value is consistent with IRRAS data at a maximum compression state of ≈ 2 A2.

We report the thin layer crystallization of high-molar mass poly(ethylene oxide) (PEO) on a liquid support using a 4 M K2CO3 aqueous solution as a subphase. Because of the Hofmeister effect, PEO does not dissolve and remains at the surface during compression on a Langmuir trough. The transition from the flat pancake conformation upon compression of the spread polymer film to an entangled monolayer results in a plateau region of the Langmuir isotherm. Using grazing incidence wide-angle X-ray scattering, the final crystallization of PEO was observed, and the crystal orientation was determined. The fold surface was (209), that is, the helix axis has a tilt angle of 2.9° to the normal vector of the water surface.

1,2,3-Triazolium salts are an important class of materials with a plethora of sophisticated applications. A series of three novel 1,3-dimethyl-1,2,3-triazolium salts with fluorine, containing anions of various size, is synthesized by methylation of 1,2,3-triazole. Their ion conductivity is measured by impedance spectroscopy, and the corresponding ionicities are determined by diffusion coefficients obtained from 1H and 19F pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy data, revealing that the anion strongly influences their ion conductive properties. Since the molar ion conductivities and ionicities of the 1,3-dimethyl-1,2,3-triazolium salts are enhanced in comparison to other 1,2,3-triazolium salts with longer alkyl substituents, they are promising candidates for applications as electrolytes in electrochemical devices.

Recent developments in synthetic pathways as simple reversible-deactivation radical polymerization (RDRP) techniques and quantitative post-polymerization reactions, most notoriously ‘click’ reactions, leading to segmented copolymers, have broadened the molecular architectures accessible to polymer chemists as a matter of routine. Segments can be blocks, grafted chains, branchings, telechelic end-groups, covalently attached nanoparticles, nanodomains in networks, even sequences of random copolymers, and so on. In this review, we describe the variety of the segmented synthetic copolymers landscape from the point of view of their chemical affinity, or synonymous philicity, in bulk or with their surroundings, such as solvents, permeant gases, and solid surfaces. We focus on recent contributions, current trends, and perspectives regarding polyphilic copolymers, which have, in addition to hydrophilic and lipophilic segments, other philicities, for example, towards solvents, fluorophilic entities, ions, silicones, metals, nanoparticles, and liquid crystalline moieties.

1,2,3-Triazole (TR) is a good proton conductor which is tidely related to formation of a hydrogen bond network along the N-HN trajectory and its self-dissociation into diH-1,2,3-triazolium and 1,2,3-triazolate. To gain a deeper understanding, the proton conductivity of TR is measured by impedance spectroscopy (IS) across its melting temperature and an additionally discovered solid-solid phase transition. The orthorhombic high temperature phase and the monoclinic low temperature modification are investigated by polarized optical microscopy, DSC- and WAXS measurements. Furthermore, the diffusion coefficients of TR are determined from IS data and measured by (1)H PFG NMR spectroscopy in the melt which allows for separate evaluation of contributions of proton hopping across the hydrogen bond network and the vehicle mechanism to the proton conductivity where the vehicles are defined as charged species generated by TR self-dissociation. Finally, the degree of dissociation of TR is calculated and the influence of the self-dissociation of TR on the proton conductivity is discussed in the context of the dielectric constant.

Block copolymers consisting of blocks of poly(amino acid)s (PAAs) derived from naturally occurring l-amino acids and biocompatibilizing poly(ethylene glycol) (PEG) are of interest for biomedical applications because of their compatibility, partial degradability, and, depending on their molecular architecture, unique self-assembly behavior. PEGylated PAAs were synthesized by α-methoxy-ω-amino PEG-initiated ring-opening polymerization, ROP, of the N-carboxyanhydrides, NCAs, of l-leucine and l-glutamic acid γ-benzyl ester. The molecular weights of the resulting di- and triblock copolymers were well controlled with narrow polydispersities, and the block copolymers were obtained in high yields (>90 %). PEGylated PAA diblock copolymers with a copolymer block of PAAs were obtained when the amino acid NCAs were polymerized as a mixture and triblock copolymers with two PAA hompolymer blocks resulted from the successive addition of the respective NCAs. Dynamic light scattering indicated that these block copolymers self-assemble when exposed to a selective solvent into micelles with hydrodynamic radii between 7 and 10 nm, which aggregate into larger structures with radii ranging between 27 and 40 nm. The coexistence and sizes of the two types of particles were corroborated by small-angle neutron scattering analyses. A detailed analysis of the micelle core structures by transmission electron microscopy suggests that the cores of the micelles do not form perfect spheres and thereby enable their continued aggregation, which is further aided by the immiscibility and subsequent phase separation of poly(l-glutamic acid γ-benzyl ester) and poly(l-leucine) blocks that constitute the PAA block.

The influence of hydrophobic modification with fatty acids of various lengths on the behavior of poly(glycerol adipate) (PGA) at the air/water interface is investigated. The Langmuir isotherm of unmodified PGA reveals a liquid expanded (LE) phase followed by film collapse as indicated by the plateau starting at πc (collapse pressure) ∼13 mN/m. The film stability increases significantly by grafting fatty acids to the PGA backbone; PGA-graft-acyl. However, it tends to decrease again for higher degree of substitution due to the decreasing number of pendant hydroxyl groups on PGA backbone, which stabilize the monolayer by forming hydrogen bonds with water molecules. For samples with higher degree of substitutions, the LE phase could not be detected in the Langmuir isotherm which only shows a sharp increase in surface pressure, corresponding to the liquid condensed (LC) phase, followed by the film collapse. Atomic force microscopy images of the Langmuir–Blodgett films depict the formation of 3D nuclei of different heights at surface pressure, π > πc and the Brewster angle microscopy images reveal the formation of buckles in the collapse region for PGA-graft-tridecyl films. The formation of a solid phase in the Langmuir film is observed only for PGA grafted with longer alkyl side chains, including, heptadecyl and heneicosanyl. Overall, it is observed that with increasing length of the acyl chains the stability and compressibility of the film on the water surface increases because of enhanced coherence between the alkyl side chains that overcomes the obstruction effect of the PGA backbone.

Cholesterol (Ch) linked to a linear-hyperbranched block copolymer composed of poly(ethylene glycol) (PEG) and poly(glycerol) (hbPG) was investigated for its membrane anchoring properties. Two polyether-based linear-hyperbranched block copolymers with and without a covalently attached rhodamine fluorescence label (Rho) were employed (Ch-PEG30-b-hbPG23 and Ch-PEG30-b-hbPG17-Rho). Compression isotherms of co-spread 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with the respective polymers were measured on the Langmuir trough and the morphology development of the liquid-condensed (LC) domains was studied by epi-fluorescence microscopy. LC domains were strongly deformed due to the localization of the polymers at the domain interface, indicating a line activity for both block copolymers. Simultaneously, it was observed that the presence of the fluorescence label significantly influences the domain morphology, the rhodamine labelled polymer showing higher line activity. Adsorption isotherms of the polymers to the water surface or to monolayers of DPPC and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), respectively, were collected. Again the rhodamine labelled polymer showed higher surface activity and a higher affinity for insertion into lipid monolayers, which was negligibly affected when the sub-phase was changed to aqueous sodium chloride solution or phosphate buffer. Calorimetric investigations in bulk confirmed the results found using tensiometry. Confocal laser scanning microscopy (CLSM) of giant unilamellar vesicles (GUVs) also confirmed the polymers' fast adsorption to and insertion into phospholipid membranes.

The behavior of a series of amphiphilic triblock copolymers of poly(ethylene oxide) (PEO) and poly(isobutylene) (PIB); including both symmetric (same degree of polymerization (DP) of the terminal PEO blocks) PEOm-b-PIBn-b-PEOm and non-symmetric (different DP of the terminal PEO blocks) PEOm-b-PIBn-b-PEOz, is investigated at the air/water interface by measuring surface pressure vs mean molecular area isotherms (π vs mmA), Langmuir–Blodgett (LB) technique, and infrared reflection–absorption spectroscopy (IRRAS). The block copolymer (PEO32-b-PIB160-b-PEO32) with longer PEO segments forms a stable monolayer and the isotherm reveals a pseudo-plateau starting at π ∼ 5.7 mN/m, also observed in the IRRAS, which is assigned to the pancake-to-brush transition related to the PEO dissolution into the subphase and subsequent PEO brush dehydration. Another plateau is observed at π ∼ 40 mN/m, which is attributed to the film collapse due to multilayer formation. The pancake-to-brush transition could not be observed for samples with smaller PEO chains. The isotherms for block copolymers, with short PEO chains, both symmetric (PEO3-b-PIBn-b-PEO3) and non-symmetric (PEO12-b-PIBn-b-PEO3), reveal another transition at π ∼ 20–25 mN/m. This is interpreted to be due to the conformational transition from a folded state where the middle PIB block is anchored to the water surface at both ends by the terminal hydrophilic segments to an unfolded state with PIB anchored to the water surface at one end. It is assumed that this transition involves the removal of PEO3 chains from the water surface in case of non-symmetric PEO12-b-PIB85-b-PEO3 and in case of symmetric, probably one PEO3 of each PEO3-b-PIB85-b-PEO3 chain. Because of the weaker interaction of the short PEO3 chains with the water surface as compared with the relatively longer PEO12 chains, the film of PEO3-b-PIB85-b-PEO3 collapses at much lower surface pressure after the transition as compared with the PEO12-b-PIB85-b-PEO3. The AFM images reveal the formation of microdomains of almost uniform height (6–7 nm) in LB films of PEO3-b-PIB85-b-PEO3 and PEO12-b-PIB85-b-PEO3 after transferring onto silicon surfaces. These domains are assumed to be the mesomorphic domains of ordered and folded PIB chains.

We studied the interaction of amphiphilic and triphilic polymers with monolayers prepared from F-DPPC (1-palmitoyl-2-(16-fluoropalmitoyl)-sn-glycero-3-phosphocholine), a phospholipid with a single fluorine atom at the terminus of the sn-2 chain, an analogue of dipalmitoyl-phosphatidylcholine (DPPC). The amphiphilic block copolymers contained a hydrophobic poly(propylene oxide) block flanked by hydrophilic poly(glycerol monomethacrylate) blocks (GP). F-GP was derived from GP by capping both termini with perfluoro-n-nonyl segments. We first studied the adsorption of GP and F-GP to lipid monolayers of F-DPPC. F-GP was inserted into the monolayer up to a surface pressure Π of 42.4 mN m-1, much higher than GP (32.5 mN m-1). We then studied isotherms of lipid-polymer mixtures co-spread at the air-water interface. With increasing polymer content in the mixture a continuous shift of the onset of the liquid-expanded (LE) to liquid-condensed (LC) transition towards higher molecular and higher area per lipid molecule was observed. F-GP had a larger effect than GP indicating that it needed more space. At a Π-value of 32 mN m-1, GP was excluded from the mixed monolayer, whereas F-GP stayed in F-DPPC monolayers up to 42 mN m-1. F-GP is thus more stably anchored in the monolayer up to higher surface pressures. Images of mixed monolayers were acquired using different fluorescent probes and showed the presence of perfluorinated segments of F-GP at LE-LC domain boundaries.

The linear biodegradable polyester poly(glycerol adipate) (PGA) was synthesized via enzymatic polycondensation using lipase B from Candida antarctica (CAL-B). Every monomer unit of PGA possesses a pendant hydroxyl group which is responsible for the hydrophilic character and moisture swelling. These OH groups were esterified to different degrees with the anti-inflammatory drug indomethacin in order to create a prodrug with a pH-sensitive linker for modified drug release. The structure of the conjugates was determined via ATR FT-IR spectroscopy, NMR spectroscopy, GPC and UV/VIS spectroscopy. The physical properties of polymers with different drug load were investigated using DSC, contact angle measurements and oscillatory rheology. Drug release was monitored over one month in vitro. A very slow, but continuous release was observed in PBS. Slightly acidic conditions and lipase activity are accelerating the indomethacin release. Therefore, poly(glycerol adipate) - indomethacin conjugates are promising prodrugs for the local sustained release of indomethacin.