bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and ordering of two‐dimensional polymers
Authors: Stupp Samuel I. 
Published: March 2011

AbstractThe work to be discussed in this lecture departs from the usual focus of polymer science on linear chains and explores the “bulk” synthesis and properties of polymer molecules that can be considered shape‐persistent molecular objects. Shapes that are particularly interesting are those not common in the conformational space of linear chains, for example, two‐dimensional polymers shaped as plates or discs and macromolecules shaped as cylinders or parallelepipeds. The lecture focuses on a molecular object which is a rigid and internally anisotropic two‐dimensional polymer with planar dimensions greater than its thickness. The shape‐granting skeleton of this two‐dimensional polymer is built by covalent bonds. We have so far developed three different strategies for their bulk synthesis, all involving systems in which reactive oligomers organize spontaneously into the necessary planar assemblies to form the object. In one strategy molecular recognition events such as homochiral interactions play a key role in the formation of the two‐dimensional flat polymers /1/. A different methodology relies on nanophase separation in rodcoil block molecules in which a rigid segment is covalently bonded to a flexible one sharing the same backbone. The third strategy involves the folding of oligomers into hairpin structures which self assemble into two‐dimensional liquids. In these two last strategies the layered rodcoils or hairpins react to form the covalent backbones necessary to grant shape to the object. A computer simulation relevant to the experimental system suggests that large two‐dimensional polymers can be formed by extremely short backbones. The lecture will also describe examples of unique properties in advanced materials that could emerge from these rigid two‐dimensional objects. These examples include. materials with self‐organized surfaces of high chemical definition and temporal stability, self assembling membranes, molecular reinforcement, and films with remarkably stable electrical or optical properties.
Fullerene grafted amine‐containing polymers
Authors: Patil Abhimanyu O. , Schriver George W. 
Published: March 2011

AbstractWe have covalently attached fullerenes to amine containing flexible hydrocarbon polymers such as amino‐ethylene propylene terpolymer (EPDM‐amine) to obtain novel fullerene functionalized polymers. These materials are soluble in solvents such as heptane or tetrahydrofuran (THF), in which the fullerene is essentially insoluble. The reaction of the fullerene and polymer was followed by infra‐red spectroscopy and viscosity measurements. Thermogravimetric analysis (TGA) scans of EPDM‐amine and Fullerene reacted EPDM‐amine show that the fullerene grafted polymer is thermoxidatively more stable than the original polymer. Furthermore, the fullerene grafted polymer could be reacted further with primary‐tertiary diamines to obtain novel polymers in which the fullerene acts as a bridging group for attaching polar functional groups to nonpolar hydrocarbon polymers.
“Living” free radical graft copolymers I: Preparation and properties
Authors: Roha Max , Wang Hsin‐Ta , Harwood H. James , Šebenik Anton 
Published: March 2011

AbstractPolymers substituted with thio groups are useful for the photochemical synthesis of graft copolymers. Such copolymers have been prepared by the initial conversion of backbone polymers containing chlorinated substituents into polymers containing diethyldithiocarbamate (TC), isopropyl xanthate (IX) or mercaptobenzothiazole (BT) functionality. The photochemical reaction of monomers with these products produced graft copolymers. A variety of halogenated polymers were investigated as starting materials for these syntheses, including poly(vinyl chloride), chlorinated polyvinyl chloride), chlorinated polyethylene, chlorobutyl rubber and neoprene. Characteristics of the grafting reactions, including “pseudo‐living” behavior and tandem grafting aspects, were investigated. Glass transitions of the grafted polymers were found to vary uniformly with composition for most of the grafted products.
Toughness of polymeric networks: The limited importance of crosslink density
Authors: Nusselder Jan Jaap H. , Bos Harriëtte L. 
Published: March 2011

AbstractFour series of polymeric model networks were prepared with bimodal chain length distribution between crosslink points and two types of dangling chains as network defects. In the last series the crosslink density was changed without a large change in the chemical composition. The fracture toughness of those networks were compared with that of the defect–free networks.The fracture toughness of the various networks is surprisingly little influenced by the introduction of defects. Neither bimodality, nor dangling chains, nor a high sol fraction alters the toughness of the network. A good correlation between KIc and the weight fraction of polyether is observed. A much smaller dependence of KIc on the strand density can be deduced. The yield stress is high and approximately invariant for all systems studied.It is concluded that the toughness of a polymeric network does not seem to be influenced by its perfection and only to a small extent by its degree of crosslinking.
Rubber‐ and thermoplastic‐modified polymer networks. Phase separation process induced by polymerization and polycondensation
Authors: Pascault Jean‐Pierre 
Published: March 2011

AbstractPolymer blends based on thermosets are very useful for many applications (toughened plastics, adhesives, composites, polymer‐dispersed liquid crystals). Generally, at curing temperature, Ti, the initial mixture of monomer(s) and additive is homogeneous. The dispersed phase results from the phase separation induced by polycondensation or polymerization of the monomer(s). The process can be looked upon as a «chemical quench» because the chemical reaction drives the change in free energy. The role of chemistry is principally to try to control the morphologies; some trends are given in this publication.
Entanglement effects in model polymer networks
Authors: Everaers Ralf , Kremer Kurt , Grest Gary S. 
Published: March 2011

AbstractMany fundamental questions for the understanding of polymer networks are more suitably addressed by current computer simulations than by experiments. Details of the microscopic topology, such as the elastically active cluster or loop entanglements, can be identified as well as controlled. In particular, it is possible to isolate and quantify their effects on macroscopic observables such as the elastic modulus. The constraints due to connectivity and conserved topology are more clearly present for networks than for melts. Already for strand lengths between crosslinks which are relatively short, the effect of the conserved topology is important. The mode relaxation in a network is significantly different from that of a melt. For weakly crosslinked systems the melt entanglement length is the relevant scaling parameter. The elastic modulus of a long chain network under ideal conditions reaches an asymptotic value which is about 2.2 times smaller than the prediction of an affine model for a network made of strands of the melt entanglement length. An analysis of the stress reveals that in the linear regime the contribution from the excluded volume is dominant compared to that from the connectivity along the strands. For larger elongations, however, the non‐linear elastic response is dominated by the chemically and topologically shortest paths through the system, where chemical crosslinks and topological entanglements between meshes of the network play a similarly important role.
Toughening of highly cross‐linked polycyanurates with epoxy‐ and phenol‐terminated butadiene‐acrylonitrile rubbers
Authors: Uhlig Christoph , Bauer Jörg , Bauer Monika 
Published: March 2011

AbstractPolycyanurate from dicyanate of bisphenol A was modified with epoxy‐ and phenol‐terminated butadiene‐acrylonitrile rubbers. Rubber‐resincopolymerisation was followed by multiple‐detection gel‐permeation chromatography (GPC). It was found that both the epoxy‐terminated and phenol‐terminated rubbers react with the cyanate and thus are covalently bound with the polycyanurate network. The influence of rubber content, acrylonitrile content and type of end group on phase structure was investigated using dynamic mechanical analysis. Fracture toughness was measured for these modifications.
Properties of networks based on poly(alkylene glycol) diacrylates
Authors: Priola A. , Bongiovanni R. , Gozzelino G. , Ferrero F. , Malucelli G. 
Published: March 2011

AbstractThree series of poly(alkylene glycol) diacrylates, namely poly(ethylene glycol), poly(propylene glycol) and poly(tetramethylene glycol) α,ω‐diacrylates have been prepared by acryloylation of the corresponding bis‐OH‐terminated oligomers. Their MW was in the range 200–1000 and their acrylic functionality was close to two. They were subjected to UV curing as thin films obtaining, by FTIR analysis, complete terminal double bond conversion in all cases with the exception of the lowest MW oligomers. Thermal and mechanical properties of the networks were investigated by means of DSC, TMA and DMTA analyses. Concerning the PPGDA oligomers, products totally amorphous and rubbery were obtained; PEGDA and PTMGDA oligomers gave similar amorphous structures with the exception of the highest MWs which showed partial crystallinity. By means of thermal and DMTA measurements, Tg values and E' moduli were obtained and correlated to the MW of the oligomers used. In particular, Tg values, as function of the crosslinking density, agreed with those calculated by the Nielsen equation for the three series investigated. The equilibrium swelling in water was determined for various networks as a function of the MW of the oligomers. The values obtained were compared and discussed in terms of the solubility parameters and the crosslinking density of various structures.
Acetylene‐terminated resins: Mechanism of thermal polymerization and properties of cured polymers
Authors: Florence Marie , Loustalot Grenier 
Published: March 2011

AbstractThe polymerization kinetics and mechanisms of model compounds (mono‐ and difunctional) characteristic of prepolymers of ATR (acetylene‐terminated resins) have been studied by HPLC, FTIR, UV, NMR (liquid and solid) and HPLC in the temperature range of 150–220°C.Using monofunctional compounds, we were able to show that the thermal polymerization of acetylene functions is not a simple reaction. Initially, the majority of compounds formed have a low polymerization degree, followed by the formation of species with higher and progressive polymerization degrees.Spectroscopic techniques such as NMR and FTIR lead to the unambiguous determination of reaction conversion up to 95% in the case of bifunctional prepolymers. The understanding of network structures, on the other hand, is more delicate in polyaromatic systems, since the chains formed are very similar to the basic skeleton of the prepolymer.The kinetic curves obtained isothermally between 150–220°C have shown that while kinetic monitoring of the disappearance of the first 90% of ethynyl functions poses no particular problems, there is a considerable uncertainty for the last 10%, regardless of the technique chosen.We have demonstrated that me thermal properties are dependent on the molecular weight and the structure of the polymer.
Use of phase diagrams in the analysis of polymer network formation
Authors: Williams Roberto J. J. , Riccardi Carmen C. 
Published: March 2011

AbstractA conversion ‐ temperature ‐ transformation (CTT) diagram was used to analyze several non‐isothermal processes of polymer network formation: a) range of heating rates where reliable kinetic information can be obtained; b) a novel process involving part of the cure in the glassy state; c) phase separation in rubber‐modified epoxies cured in heated molds.
Microscopic structure and viscosity behaviours of ion‐complexed polymer gels
Authors: Shibayama Mitsuhiro , Ikkai Fumiyoshi , Nomura Shunji 
Published: March 2011

AbstractPoly(vinyl alcohol)‐Congo Red (PVA‐CR) complexes in aqueous solutions have a unique sol‐gel transition behaviour. At an appropriate PVA concentration, a sol‐gel‐sol‐gel type reentrant transition takes place with increasing CR concentration. The microscopic structure and Theological properties of these complexes were investigated by small‐angle neutron scattering (SANS) and viscometry.
Fatigue crack growth in crosslinked polymers
Authors: Fischer Michael , Martin Denis , Pasquier Maurice 
Published: March 2011

AbstractDo crosslinks between the molecular chains of a glassy polymer impede the growth of fatigue cracks? Three polymers H, M, and L of equal chemical composition but differing in crosslinking densities were prepared by the polyaddition reaction of stoichiometric mixtures of 1,4‐butanediol diglycidyl ether, N,N'‐dimethylethylenediamine, and 1,4‐diaminobutane. The growth of the fatigue cracks under cyclic loading (2 Hz) was studied in the glassy polymers at ‐100°C and ‐60°C with the help of strain gauges bonded to the back side of the compact tension specimens. Crack growth rate da/dN ranged from a few nm to 10 μm depending on the stress intensity amplitude K̂1/2 at the crack tip. Log (da/dN) plotted against K̂1 revealed a linear relationship in accordance with the model calculation. The slopes, m, of the straight lines characterizing the fatigue crack growth were found to scale with M̄‐1/2 in the case of the studied polymers. (M̄c: average molar mass of chain segments between crosslinks). Glassy polymers with a low degree of crosslinking are less prone to fatigue crack growth than are the more tightly crosslinked polymers, as shown by the presented examples.
Hydrogen bonded polymer blends and the design of miscible polymeric antioxidants
Authors: Coleman Michael M. , Yang Xiaoming , Stallman John B. , Painter Paul C. 
Published: March 2011

AbstractThe relative magnitude of the equilibrium constants describing self‐association versus inter‐association is an important factor in determining the phase behavior of polymers that hydrogen bond. In studies of sterically hindered phenolics we have found that poly(2,6‐diisopropyl‐4‐vinylphenol) (PDIPP) only moderately self‐associates, but strongly inter‐associates with polymers containing groups such as ester carbonyls, ether oxygens, and the like. PDIPP is miscible with polytetrahydrofuran (PTHF) and simultaneously acts as an efficient polymeric antioxidant. This result points the way to the design of specific miscible polymeric antioxidants for polar polymers.
Structure and interactions in homopolymers and blends as studied by the methods of vibrational and nmr spectroscopy
Authors: Dybal Jiîí , Straka Jaroslav , Schneider Bohdan , Schmidt Pavel 
Published: March 2011

AbstractThe combination of IR, Raman and NMR spectroscopy was used in the study of the blends of semicrystalline and amorphous polymers with considerably different strength of intermolecular interactions: poly(ϵ‐caprolactam)/polystyrene (PCL/PS), poly(ethylene oxide)/poly(methyl methacrylate) (PEO/PMMA) and poly(N‐methyllaurolactam)/poly(4‐vinylphenol) (PNMLL/PVPh). In the vibrational and NMR spectra of the blends composed of non‐interacting polymers (PCL/PS) and weakly interacting polymers (PEO/PMMA), no band changes were observed which would indicate changes of the conformational structures. 1H NMR relaxation of the PCL and PS components in the blends is the same as in the respective homopolymers similarly treated. In the blends of weakly interacting polymers (PEO/PMMA), the crystallinity of PEO is influenced by the presence of PMMA and is negligible in the blends with less than 30 wt.‐% of PEO. The rotating‐frame spin‐lattice relaxation time for protons TH1p of PMMA indicates close contact of the PMMA and PEO chains. In the blends PNMLL/PVPh with strong hydrogen‐bonding interactions, both components are intimately mixed on a scale of 3–4 nm and significant shifts of some bands both in vibrational and in NMR spectra reveal changes of structure.
Epoxy resins and epoxy blends studied by near infra‐red spectroscopy
Authors: Chabert B. , Lachenal G. , Vinh Tung C. 
Published: March 2011

AbstractThe cure and the final network of epoxy resins have been investigated by numerous techniques, nevertheless a clear understanding of this network structure has not yet been achieved. FTIR analysis of polymeric materials provides highly precise measurements that are widely interpretable in terms of chemical structure. Yet the high absorption of fundamental bands requires careful sample preparation to reduce the thickness of the sample or special reflection techniques are needed. Furthermore, the occurrence of overlapping bands for epoxy resin (N‐H and O‐H vibrations in the 3000 cm−1 region) renders the quantitative analysis in the region mid IR particularly difficult. However, the overtone and combination bands are 10–100 times weaker than the fundamental ones and are observed in near infrared (NIR) region. Longer pathlengths than Mid IR ones can be used allowing transmission analysis of thick samples (1‐20 mm) without special preparation. NIR absorption bands have different intensities depending on the anharmonicity of vibrations. The strongest absorption bands are due to protons connected to carbon, nitrogen, oxygen. Hydrogen bonding due to inter‐ and intramolecular interactions can cause band broadening, peak position shifts and intensity variations. NIR spectroscopy is therefore a useful technique to investigate polymeric materials and was used to study the cure reactions of various epoxy resins cured with amine hardener. Using different NIR techniques (reflectance, transmission and microscopy) we will briefly present some results concerning hydrogen bonding between epoxy and amine hardener before curing, epoxy resins, glass/epoxy composites and epoxy/PES (polyethersulfone) blends.
Ir‐ spectroscopy of hydrogen bond as a method of analytical determination of physical network in poly(ether urethane)s
Authors: Strikovsky Alexander G. , Zharkov Vadim V. , Letunovsky Mihail P. 
Published: March 2011

AbstractThe equilibrium association of urethane groups in a series of 4, 4′ ‐ diphenylmethane diisocyanate (MDI)/polypropylene oxide) (PPO) based poly(ether urethane) elastomers (PUE) was studied on the basis of IR‐spectroscopy data. The concentration of associates containing 2,3 and 4 urethane groups is calculated, which permits immediate monitoring of changes in PUE mechanical properties using the model of a physically cross‐linked polymer.
Ftir study of hydrogen bonding and phase behaviour in poly(vinylpyridines)/poly(ethylene‐CO‐vinyl alcohol) blends
Authors: Isasi José R. , Cesteros Luis C. , Katime Issa A. 
Published: March 2011

AbstractThe specific interactions between polyvinylpyridines and ethylene‐vinyl alcohol copolymers of different compositions have been studied by Fourier transform infrared spectroscopy (FTIR). Hydrogen bonding between both polymer components leads to significant spectral modification in pyridine rings spectral bands. Minor modifications in other spectral modes have been also detected. The spectral results indicate at least three competing equilibria processes in the blends: hydroxyl‐hydroxyl copolymer self‐association and hydroxyl‐pyridine interassociation. Painter‐Coleman association model was successfully applied and the phase diagram for these systems has been predicted.
A simple method of calculation of vibrational spectra of long‐chain aliphatic compounds and their urea adducts
Authors: Puchkovskaya Galina A. , Sekirin Igor V. , Aryutkina Natalya L. 
Published: March 2011

AbstractA semi‐quantitative method for calculation of the LCAC's and their urea adducts vibrational spectra based on simple model Hamiltonian on the basis corresponding to excitations of fragments forming the studied system is proposed. A comparison with experimental spectra of LCAC's with different terminal groups and in different phase states is performed. It is shown that the effect of the built‐in incommensurability of polymethylene chain and urea lattice in adducts must manifest itself as additional broadening of some bands in the vibrational series of polymethylene chain. The manifestation of possible resonance of “host” and “guest” vibrations has also been analyzed.
NMR study of ordering in liquid crystalline solution of polybenzylglutamate of various molecular mass
Authors: Khachaturov A. S. , Koltsov A. I. , Roth H. , Shabsels B. M. 
Published: March 2011

Abstract1H and 2H NMR spectra of fractionated poly‐γ‐benzyl‐L‐glutamate solutions are recorded at various temperatures. NMR signals of both these nuclei of solvent molecules (mixture of CD2Cl2 and CH2Cl2) appear to be doublets. Their splitting (30‐130 Hz for protons and 200–600 Hz for deuterons) reduces when the polymer molecular mass grows. As the splitting is proportional to degree of orientation of solvent and solute molecules, it means that longer macromolecules are less oriented than shorter ones. One can explain such behavior in terms of persistent chain model, since the bended rods of less length can be better oriented along the director.
Towards the selective synthesis of macrocyclic vinyl polymers of controlled size
Authors: Deffieux Alain , Schappacher Michel , Rique‐Lurbet Laurence 
Published: March 2011

AbstractA new strategy for the synthesis of vinyl type macrocyclic polymers of controlled molecular weight and molecular weight distribution has been investigated. It involves the direct coupling of an α‐ω‐heterodifunctional linear polymer precursor previously prepared by living polymerization. The cyclization is achieved under high dilution, by an appropriate activation of one of the polymer‐ends in order to allow its reaction with the other end function. Its application to the preparation of polystyrenes and poly(vinyl ether)s with a macrocyclic structure, as well as ring closure mechanisms in the presence of different cyclization agents are reported.
Rheological behavior of comb‐shaped mesophase polymers and their modifying role in the blends with thermoplastics
Authors: Plate N. A. , Talroze R. V. , Rogunova M. A. , Zubarev E. R. 
Published: March 2011

AbstractMost of the polymers with mesogenic groups in side‐ or main‐chains are liquid‐crystalline in nature. One can observe a lot of similarities in the mesophase structure types, orientational order parameter, anisotropy of optical, electrical and magnetical properties of polymer and low‐molecular‐weight liquid crystals. At the same time the presence of backbones contributes some peculiarities and limitations to their behavior.
Micro‐composite systems by in‐situ formation of liquid crystal polymers in commodity polymers
Authors: An Jeongwoong , Ichikawa Tsuneko , Ogata Naoya 
Published: March 2011

AbstractIn‐situ formation of polyimide was carried out in solution of copolymers derived from styrene and 4‐vinylpyridine. The in‐situ formed polyamic acid formed a strong hydrogen‐bonding with pyridine moiety of the copolymers, resulting in homogeneous solutions. Cast films obtained from the solutions were clear and transparent without phase separations, and mechanical properties of the films were much stronger than those of films from the original copolymers. In‐situ polymerization of acrylamide in poly(styrene) was carried out by anionic polymerization to form Nylon 3 which was dispersed in poly(styrene) as fine particles, and mechanical properties of the poly (styrene) were greatly improved.