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A onepot solution polymerization under mild conditions was adapted for the synthesis of welldefined aliphaticaromatic polyesters with different degrees of branching. The esterification was performed at room temperature using 4,4bis4′hydroxyphenylvaleric acid AB2 and 34hydroxyphenylpropionic acid AB as monomers. DPTS was used as a catalyst and DCC as a coupling agent. Polyesters with statistical, dendritic topology, controlled degree of branching and $\overline M _{\rm w}$ > 35 000 g · mol−1were obtained. The polymers were characterized by 1H and 13C NMR, SEC, DSC, and TGA. A strong dependence of the degree of branching and the thermal properties of the polymers depending on the ABAB2monomer ratio was observed.

New thermoresponsive graft copolymers were synthesized by the cationic ring-opening polymerization of 2-methyl-2-oxazoline (MeOxa) or 2-ethyl-2-oxazoline (EtOxa), initiated by the random copolymers of chloromethylstyrene (CMS) and N-isopropylacrylamide (NIPAAm) using the “grafting from” method with a yield of 66−94%. The polymers were characterized by NMR, GPC, and DSC, and the conformational transition (lower critical solution temperature, LCST) of macroinitiators and graft copolymers was determined by the turbidity and DSC measurements. The transition temperature of the graft copolymers could be fine-tuned through the composition of the macroinitiator and the graft copolymer. An increasing quantity of the hydrophobic comonomer chloromethylstyrene in the macroinitiator lowered its LCST, while in the graft copolymer an increasing content of the hydrophilic segment of poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline) raised the transition temperature. For graft copolymers with a high content of long poly(2-alkyl-2-oxazoline) grafts, stabilized aggregates with a thermoresponsive core can be formed at the LCST instead of precipitation of the material.

We studied the bulk and surface properties of maleimide (MI) copolymers based on three different main chains, poly(ethene-alt-maleimide), poly(styrene-alt-maleimide), and poly(octadecene-alt-maleimide), with two different types of side chains (4-(N-perfluoroheptylcarbonyl)aminobutyl and n-dodecyl). By the given alternating substitution pattern of the side chains in MI copolymers, different side chain organizations caused different surface energetics. On the basis of determined advancing contact angles of water on spin-coated MI copolymer films, solid surface tensions γsv were calculated in the range of 19−23 mJ/m² for alkyl side chains and of 11−18 mJ/m² for fluorinated side chains. In both cases, within the aliphatic and fluorinated series, the main chain poly(styrene-alt-maleimide) suppressed a better alignment of side chains resulting in nondensely packed CH3 and CF3 surface groups, respectively, and higher solid surface tensions. For this study small- and wide-angle X-ray diffraction, differential scanning calorimetry, attenuated total reflection infrared spectroscopy, ellipsometry, atomic force microscopy, contact angle measurements, angle-resolved X-ray photoelectron spectroscopy, and molecular modeling calculation were used to investigate the bulk and surface properties.

Sequential copolymerizations of trimethylene carbonate (TMC) and l-lactide (LLA) were performed with 2,2-dibutyl-2-stanna-1,3-oxepane as a bifunctional cyclic initiator. The block lengths were varied via the monomer/initiator and via the TMC/l-lactide ratio. The cyclic triblock copolymers were transformed in situ into multiblock copolymers by ring-opening polycondensation with sebacoyl chloride. The chemical compositions of the block copolymers were determined from ¹H NMR spectra. The formation of multiblock structures and the absence of transesterification were proven by ¹³C NMR spectroscopy. Differential scanning calorimetry (DSC), wide-angle X-ray scattering (WAXS), and dynamic mechanical analysis (DMA) measurements confirmed the existence of a microphase-separated structure in the multiblock copolymers consisting of a crystalline phase of poly(LLA) blocks and an amorphous phase formed by the poly(TMC) blocks. Stress−strain measurements showed the elastomeric character of these biodegradable multiblock copolymers, particularly in copolymers having ε-caprolactone as comonomer in the poly(TMC) blocks.

Interactions of phenolic and carboxylic group containing chromophores (hydroxyarylidene alkanones) with polyamidines were investigated by UV/vis and ¹H NMR spectroscopy. Because of the strong basicity of the polyamidines, deprotonation of the chromophores was observed. Deprotonation of the phenolic group is accompanied by a change of the electronic structure of the chromophore resulting in a strong bathochromic shift of the longest wavelength absorption band. Increased interactions are observed after introduction of a carboxylic group into the chromophore. It could be shown that deprotonation of the carboxylic group is favored so that the deprotonation of the phenolic group only starts after a major part of the carboxylic groups is deprotonated. In highly diluted solutions, the interaction of the carboxylic group with the polyamidine also increase the extent of deprotonation of the phenolic groups. A physical network formation is assumed that also increases the glass transition temperatures of the mixtures strongly.

Five kinds of polylactides (PLAs), with different D-lactide contents and tacticities, were subjected to high-speed melt-spinning experiments. In addition to stereochemical purity, the PLA types differed in molecular mass and molecular mass distribution. The properties of the different PLA materials were characterized by thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis, size exclusion chromatography, and ¹H-NMR and ¹³C-NMR spectroscopy. The material was spun with a high-speed spinning process within the range 2000–5000 m/min. The physical and tensile properties of the fibers were determined. The maximum tensile properties of the fibers were a 300 MPa tenacity at an elongation at break of 30% and a tensile modulus of 6.8 GPa. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 800–806, 2004

The synthesis of aliphatic−aromatic poly(ether amide) dendrimers via ring-opening addition reaction of phenol groups toward oxazoline up to generation 3 is presented. The first and second generation could be prepared both by convergent and divergent approaches. The ring-opening addition reaction was carried out in bulk at temperatures between 140 and 190 °C, followed by hydrogenation of the protecting benzyl ether units with palladium catalyst. The dendrons and dendrimers were characterized by ¹H and ¹³C NMR spectroscopy, MALDI−TOF MS, SEC, and DSC. The synthetic scheme applied allowed to prepare perfect dendrimers having identical structure and end groups as previously described hyperbranched polymers which enabled a direct comparison of the properties. Melt rheology measurements on the dendrimers revealed a predominantly elastic behavior with a relatively high viscosity at low frequency, as was found also for the hyperbranched analogues. The second generation of one of the poly(ether amide) dendrimers was mixed with linear polyamide 6 (PA6) in melt up to an amount of 1 wt % in order to evaluate the influence of dendrimers on the properties of the matrix. The dendrimer was fully miscible with the matrix, but in contrast to the hyperbranched polymers of higher molar mass, it had no influence on the melt rheological behavior of the PA6.

Allyl-terminated polystyrenes (PS macromonomers) were synthesized by quasiliving atom transfer radical polymerization (ATRP) of styrene followed by carbocationic chain end transformation with allyltrimethylsilane in the presence of titanium tetrachloride. Systematic investigations were carried out on metallocene/MAO-catalyzed copolymerization of PS macromonomers with propene by varying the molecular weight of the macromonomer, the type of catalyst, the polymerization temperature, and the propene pressure. The resulting poly(propene-g-styrene) (PP-g-PS) graft copolymers were analyzed by ¹H and ¹³C NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry. Macromonomer incorporation, molecular weight, tacticity, and crystallinity of the resulting PP-g-PS copolymers were greatly influenced by the investigated parameters. The macromonomer incorporation depends mostly on the polymerization temperature. The highest comonomer incorporation (10.8 wt %) was achieved at the highest polymerization temperature, but at the same time the molecular weight decreases strongly with increasing polymerization temperature leading to graft copolymers with relatively low molecular weights. For the first time, the effect of well-defined PP-g-PS grafts was investigated on blending incompatible polypropylene with polystyrene. Surprisingly, it was found that PP-g-PS graft copolymers with short PS side chains show a better compatibilization efficiency than those with long PS chains at comparable composition as scanning electron microscopic investigations on the morphology of blends indicate.

The kinetics of the polycondensation of 3,5-bis(trimethylsiloxy)benzoyl chloride (BTMSBCl) was investigated. 1D and 2D NMR techniques were applied to achieve a complete signal assignment of the structural units of the resulting polymer (poly(3,5-dihydroxybenzoic acid), PDHBA), which was obtained after hydrolysis of the trimethylsiloxy and the acid chloride groups. Furthermore, the diads could be identified. After quantification of the signals by ¹³C NMR spectroscopy, a data set of ratios of structural units as a function of the conversion had been studied with respect of the kinetics of the system and their resulting structural composition. Since the data do not follow the ideal conversion dependence, the relative rate constants of the 12 different basic reaction steps were determined by simulation, which fit the obtained data best. A study of the sensitivity of the reaction curves to changes in the individual rate constants showed large differences and helped to distinguish the importance of the different basic reactions to the overall reaction. One kinetic situation was identified as dominant. The deviations (from the ideal conversion dependence) were explained by different electronic effects on the reaction sites caused by the successive substitution of siloxy and benzoyl chloride groups by ester groups on the aromatic ring. Analysis of the data for the diads indicated no further kinetic effect.

The existence of ether byproducts could be clearly proven for the hyperbranched polymerization of 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) using NMR spectroscopy. Polymerization experiments were performed under standard conditions with different catalysts. The ether structures were identified by characteristic ¹³C NMR signals of the quarternary carbons and of the ether methylene carbons. Different substitution pattern of these ether units could be distinguished. Using high-resolution magic-angle spinning (HR-MAS) NMR spectroscopy also cross-linked, swollen samples could be analyzed. The amount of ether side products was calculated from ¹H NMR spectra after alkaline hydrolysis of the polymer samples. Etherification can occur as an intramolecular reaction resulting in cycles. Intermolecular etherification results in molecules with two or more focal groups which can act as cross-linker in the polymerization. Thus, cross-linked samples were obtained at high degrees of conversion.

A first generation dendrimer D1 was placed onto defined surfaces to study the excitation energy transfer between D1 as donor molecule and a pyrene containing polymer 213 as acceptor molecule in Langmuir−Blodgett (LB) multilayers. Fluorescence experiments were carried out at several excitation wavelengths (220, 260, 312, and 341 nm). D1 formed a closed LB layer with a collapse area of 73 Ų on an aqueous subphase, and a successful incorporation of D1 in LB multilayers onto quartz plates was possible. At 220 nm excitation wavelength the adjacent donor and acceptor layers showed a dramatically increased fluorescence activity of the pyrene group in 213, which is about 20 times higher than that of the acceptor layer 213 without the present donor layer D1. 213 quenches the fluorescence activity of D1 more than 90% although only 5% of the maleic acid groups in 213 are labeled with pyrene. The excitation energy transfer between D1 and 213 may be assumed as a Förster energy transfer which was examined versus distance with two, four, six, and eight interlayers of an amphiphilic copolymer 12 between D1 and 213.

The structure of hyperbranched aromatic polyamides synthesized from different ratios of p-phenylenediamine and trimesic acid (A2 + B3 reagent pair) has been investigated by means of ¹H and ¹³C NMR spectroscopy. On the basis of a detailed NMR signal assignment six 1,3,5-trisubstituted benzene moieties with different substitution patterns can be distinguished. The different monomer ratios influence the polymer architecture with respect to the content of these substructures, the degree of branching and the predominant functionalities (COOH or NH2). An excess of B3 results in a larger number of branches and a predominant COOH functionalization. ¹H NMR proves site-specific interactions between lithium cations and the polymer substructures. The observed chemical shift effects simplify the quantification of the spectra. Finally, acetylation of amino groups by acetic acid, an impurity in commercial trimesic acid, could be proven.

The synthesis of novel poly(ether amide) dendrimers containing different symmetrical benzenetriamides as core molecules is presented. The synthesis was carried out in a stepwise convergent manner to build up poly(ether amide) dendrons where 5-(2-aminoethoxy)isophthalic acid is the branching repeating unit. Three defined dendrons were subsequently attached to a central core. For this key reaction step O-(benzotriazol-1-yl)-N,N,N‘,N‘-tetramethyluronium tetrafluoroborate (TBTU) was preferably used as activating agent to form the desired amide groups. ¹H/¹³C NMR spectroscopy, MALDI-TOF-MS, SEC, and DSC were used to characterize the obtained dendrimers. The incorporated central units had a remarkable influence on the glass transition temperatures (Tg) within the series of dendrimers.

The kinetics of reactions with nonuniform reaction rate constants leading to hyperbranched polymers has been examined and discussed. A matrix notation was developed, which has then been applied to the analysis of the kinetics of AB2, AB3, ABn, and ABB‘ systems. All differential equations have been integrated numerically in order to obtain plots of the ratios of structural units as functions of the conversion. Three general situations for AB2 systems and the kinetics of self-condensing vinyl polymerization as one example of an ABB‘ system are discussed. It was found that the influence of the first B group on the reactivity of the second B group has the largest effect on ratio of structural units and final composition. Thus, by varying the rate constants of these reaction steps in the model the resulting degree of branching ranges between 15 and 89%. Furthermore, the diad formation of the AB2 system is analyzed.

Metal complexes of salicylideneamines exhibit very interesting properties and have been well characterized since the late 1920s. Amphiphilic salicylideneamines have been synthesized in order to introduce such complexes in Langmuir−Blodgett multilayers. They do not hydrolyze under the applied experimental conditions and form stable monolayers. On subphases containing transition metal ions, these compounds form square-planar metal complexes by an interfacial reaction. Monolayers of these complexes have been transferred onto solid substrates to prepare Langmuir−Blodgett multilayers. Spectroscopic measurements with polarized light indicate an orientation of the complex plane nearly parallel to the substrate surface. In addition, monolayer experiments with presynthesized amphiphilic metal complexes have been carried out. Available hydroxyl groups in such complexes may be exploited to construct aggregates due to the ability of the molecules to form intermolecular bonds. Monolayers of these aggregates have also been used for the preparation of multilayers.