The kinetics for the acidic hydrolysis of two water-soluble poly(2-oxazoline)s with methyl and ethyl substituents were investigated. It could be observed that poly(2-ethyl-2-oxazoline) (PEtOx) and poly(2methyl-2-oxazoline) (PMeOx) are hydrolyzed following a linear relation with time. Various polymer lengths and concentrations were investigated, revealing that both parameters had no influence on the hydrolysis kinetics. Comparison between PEtOx and PMeOx revealed that the smaller PMeOx side group could be removed faster. Furthermore, a series of linear poly(ethylene imine) (PEI) were synthesized with varying M/I ratio from 5 to 200 to elucidate structure-property relations. Thermal measurements indicated that the T g of PMeOx was increasing up to a M/I ratio of 100. PEI, on the other hand, is crystalline and exhibits a melting temperature which shows a similar increase with M/I ratio as observed for the T g of PMeOx. Solubility measurements in water and water/ethanol mixtures indicated a solubility transition to a soluble state at elevated temperatures. The solubility transition was observed to fit with the melting temperature, indicating that the PEI crystals need to melt in solution before solubilizing. Moreover, when adding ethanol to the water solution, the formed crystals are less stable due to the improved solubility of PEI in ethanol, causing a decrease in cloud point temperature. Upon cooling, PEI crystallizes at much lower temperatures compared to dissolution, causing a large hysteresis presumably due to extensive intermolecular hydrogen bonding, which also plays a role in the formation of the hydrate crystals.

[a] Ruthenium(II) polypyridyl complexes have received particular interest with respect to photosensitizer applications, because they are stable and inert complexes that show a defined metal-to-ligand charge transfer (MLCT).[1] A central dilemma is that trisbidentate complexes (e.g., of 2,2'-bipyridine, bpy) show long excited-state lifetimes, whereas bis(tridentate) complexes (e.g., of 2,2':6',2''-terpyridine, tpy) allow the isomer-free construction of linear assemblies for vectorial electron-transfer processes.[2] The quest of diminishing the fast radiationless deactivation of the 3 MLCT state through the triplet metal-centered state ( 3 MC) of bis(tridentate) ruthenium(II) polypyridyl complexes [3] has motivated numerous approaches [4][5][6] that aim at 3 MLCT lowering or 3 MC raising or both. Ideally, electronic manipulations are realized by direct incorporation of stronger donors, that is, by cyclometalation [7] or coordination through anionic N-heterocycles [8] and N-heterocyclic carbenes (NHCs).[9] Thereby, strong s and p donation by coordination through anionic carbon or nitrogen donors lead to a destabilized ground state and, thus, a lowered 3 MLCT, resulting in a radiationless deactivation governed by the energy-gap law [10] and a low driving force for the potential electron-transfer processes. In contrast, classical NHC ligands are strong, charge-neutral s donors and p acceptors, thus causing a favorable 3 MC destabilization, but also undesirably blue-shifted MLCT transitions. Alternatively, the expansion to six-membered ring chelators [6] leads to excellent excited-state lifetimes by a more favorable bite angle, but can also cause the formation of isomers (fac, mer) that show very different properties and that are hard to separate.In this regard, abnormal or mesoionic carbene ligands [11] provide superior s-donating and only moderate p-accepting properties that ideally would lead to strongly destabilized 3 MC states and a maintained 3 MLCT energy. 1,2,3-Triazolylidenes match these demands and are readily accessible by modular click chemistry. Herein we present a heteroleptic bis(tridentate) ruthenium(II) complex (RuCNC) of the new 2',6'-bis(1-mesityl-3-methyl-1,2,3-triazol-4-yl-5-idene)pyridine (CNC) ligand and the parent tpy. A heteroleptic complex with tpy is particularly interesting, because it preserves the elaborated terpyridine chemistry, including a variety of ruthenium precursors, allows for asymmetric functionalization, and includes a reference ligand. The electronic and optical properties of RuCNC were investigated by experimental and theoretical studies.The synthesis of RuCNC was achieved under mild reaction conditions with a high selectivity and reasonable yield (Scheme 1). For the preparation of 2',6'-bis(1-mesityl-3-methyl-1,2,3-triazolium-4-yl)pyridine tetrafluoroborate (H 2 CNC), the parent click-derived 2',6'-bis(1-mesityl-1,2,3-triazol-4-yl)pyridine (tripy) [12] could be methylated selectively with Meerweins salt [13] as evidenced by single-crystal Xray diffraction (Figure ...

The detailed characterization of macromolecules plays an important role for synthetic chemists to define and specify the structure and properties of the successfully synthesized polymers. The search for new characterization techniques for polymers is essential for the continuation of the development of improved synthesis methods. The application of tandem mass spectrometry for the detailed characterization of synthetic polymers using the soft ionization techniques matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and electrospray ionization mass spectrometry (ESI-MS), which became the basic tools in proteomics, has greatly been increased in recent years and is summarized in this perspective. Examples of a variety of homopolymers, such as poly(methyl methacrylate), poly(ethylene glycol), as well as copolymers, e.g. copolyesters, are given. The advanced mass spectrometric techniques described in this review will presumably become one of the basic tools in polymer chemistry in the near future.

A series of rigid π-conjugated bis(terpyridines) (M1−M7) bearing electron-acceptor spacer units in 4′-position was synthesized in moderate to high yields by Pd0-catalyzed Sonogashira cross-coupling reactions. The compounds were fully characterized by NMR spectroscopy, MALDI−TOF mass spectrometry, elemental analysis and their photophysical properties were discussed in detail. These new bis(terpyridines) were applied for the self-assembly reaction with ZnII ions to form metallo-homo polymers (P1−P7). Broadened NMR signals and UV−vis titration experiments confirmed the successful polymerization. The electro-optical properties of the materials were investigated in detail. Band gaps up to 2.08 eV and bright blue to orange photoluminescence with quantum yields of 18 to 66% were observed strongly depending on the nature of the π-conjugated bis(terpyridine) system. In combination with electron-donor ditopic terpyridine ligands (MD1 and MD2), two ZnII random copolymers (R1 and R2) were synthesized. These materials were investigated by UV−vis absorption and photoluminescence experiments in dilute solution and in the solid state, prepared by spin-coating from DMF solutions. Thereby, random copolymer R2 featured an energy transfer from the donor to the acceptor part in dilute solution.