Synthesis of novel bifunctional hindered amine-UV absorber polymer stabilizers

The synthesis of new stabilizer compounds (a combination between 2,2,6,6-tetramethylpiperidine and 2-hydroxyphenylbenzotriazole in one molecule) is reported. Four polymerisable combined stabilizers as well as two unsaturated triazinyl-2,2,6,6-tetramethylpiperidines and two unsaturated triazinyl-2-hydroxyphenylbenzotriazoles as individual stabilizers were synthesized. Their copolymers and terpolymers of the individual stabilizers with acrylonitrile were obtained. Chemical bonding of the stabilizers in the polymer was confirmed spectrophotometrically. The influence of these additives on the photo-stability of the copolymers was studied. The participation of the combined stabilizers in the polymerisation did not significantly affect the molecular weight and polydispersity of the copolymers. A significant stabilizing effect against photodegradation was found.     

Structure of phenolic stabilizers for polymers VIII. Crystal structure of 2,2′-methylenebis(4-methyl-6-ter-butylphenol) monoacrylate

L. Ya. Karpov Scientific-Research Physicochemical Institute. Scientific-Research Institute of Rubber and Latex Goods. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 162–164, September–October, 1991.     

Molecular model of phenolic polymer dissolution in photolithography

The resolution of photolithographic processes has advanced to the point that difficulties, such as line‐edge roughness, associated with phenomena occurring at molecular length scales are becoming important. In order to control these phenomena, it is necessary to understand them. To that end, a numerical model has been used to simulate the dissolution of phenolic polymers in aqueous base. The simulation applies the Critical Ionization Model to a rectangular‐lattice representation of the polymer matrix. The model has been adapted to describe the dissolution process that is responsible for photoresist function. Both continuum and molecular versions of the model are presented. The Continuum Model yields dissolution profiles that approximate the contours of the calculated spatial variations in chemical blocking (blocking profile). An algorithm has been developed to connect individual cells to form polymer chains, and to fill the lattice in a way that produces a Gaussian chain length distribution. The model employs only a single adjustable parameter, the time‐step correction factor (assuming one can measure the probability of ionization once a site encounters the developer). The Molecular Model predicts a dissolution rate that decreases non‐linearly with respect to degree of chemical blocking, as is observed experimentally. Dissolution profiles can be generated with the Molecular Model based either on this calculated dependence of the dissolution rate on blocking fraction or from direct application of the model to a blocking profile. The probabilistic nature of the model introduces edge roughness of the same degree as that observed experimentally. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2103–2113, 1999     

Morphology and thermodynamics of selenium-containing nanosystems: The effect of polymer stabilizers

Nanosystems based on zero-valent selenium and biocompatible polymer stabilizers (polyvinylpyrrolidone with molecular weight (MW) М _w = (10–55) × 10³, poly-N,N,N,N-trimethylacryloyloxyethylammonium methylsulfate with М _w = (30–250) × 10³ and polyethylene glycol with М _w = (1–40) × 10³) are studied by means of static and dynamic light scattering, and the resulting data are compared. Dense spherical multimolecular nanosystems are found to be formed. Morphological and thermodynamic characteristics of selenium-containing nanosystems, depending on the nature and MW of the polymer stabilizer, are determined. It is shown that the properties of nanosystems can be adjusted by varying the molecular weight of the polymer stabilizer.     

A new antagonism between hindered amine light stabilizers and acidic compounds including phenolic antioxidant

Hindered amine light stabilizers (HALS) are known to show antagonism with acidic compounds including phenolic antioxidants. In this study it was found that a hydroperoxide-decomposing reaction by HALS is accelerated in the presence of an acidic compound, and that the decomposition proceeds homolytically. Even weak acids such as a phenolic antioxidant induced the antagonism. On processing plastics at a high temperature, it is thus important to decompose hydroperoxides heterolytically as efficiently as possible. The data found in this study suggest that salts of HALS with an acid such as 2,6-di-tert-butyl-4-methylphenol (BHT) may produce free radicals which accelerate the decomposition of plastics. The role of HALS nitroxides in the decomposition of hydroperoxides is also discussed.     

Structure of algal-born phenolic polymeric adhesives

Adhesive materials extracted from the brown alga Fucus serratus are composed of phenolic polymer, alginate, and CaCl2. The phenolic polymer undergoes an oxidation reaction in the presence of bromoperoxidase, KI, and H2O2. The nanostructure of the adhesive was investigated using small angle X-ray scattering, light scattering, and cryo- transmission electron microscopy experiments. These have shown that the phenolic polymer undergoes self-assembly and forms flexible chain-like objects. Oxidation or adding alginate does not alter this structure. However, once calcium ions are added, a rigid network is formed. Presumably, this network is responsible for the cohesive strength of the glue.     

Surface modification of polymers. III. Grafting of stabilizers onto polymer films

Polypropylene, polystyrene, and polyethylene have been grafted with glycidyl acrylate and glycidyl methacrylate. After 5 min of grafting with UV irradiation, polystyrene was extensively grafted to 91% coverage of glycidyl acrylate according to ESCA, while polypropylene was grafted to only 50% coverage. With glycidyl acrylate the grafting depth is estimated to be 0.1 μm for PP and 0.23 μm for PS. Glycidyl methacrylate is grafted in a thinner layer than glycidyl acrylate. The stabilizers 2,4-dihydroxybenzophenone, phenyl 4-aminosalicylate, and 4-amino-2,2,6,6-tetramethylpiperidine were attached to LDPE surfaces containing grafted glycidyl acrylate by opening of the epoxide bond. The reaction between epoxide and stabilizer is diffusion controlled at high concentrations of stabilizer. UV spectroscopy on an LDPE film grafted and reacted with 2,4-dihydroxybenzophenone showed that 227 nmol stabilizer/cm² was bound to the surface.     

Chemiluminescence of polyethylene: The comparative antioxidant effectiveness of phenolic stabilizers in low‐density polyethylene

The thermal stabilizing efficiency of a range of phenolic antioxidants (Lowinox CA22, Lowinox WSP, Lowinox TBP6, Irganox 3114, Irganox 1330, and Cyanox 1790) was determined in polyethylene films with chemiluminescence and hydroperoxide analysis and compared with standard systems based on Irganox 1010 and 1076. Under both nitrogen and oxygen conditions, good correlations were obtained between the two methods, confirming the importance and role of the hydroperoxide functionality and its stability in the oxidative process. Chemiluminescence decay rates correlated well with the initial corresponding hydroperoxide contents, which were measures of the antioxidant efficiencies in the polymer. The antioxidant structure and volatility (melting points) were important parameters to consider in any such correlations and related very much to the methodology and conditions of analysis (i.e., the temperature and atmosphere). Some of the antioxidants themselves under nitrogen exhibited strong chemiluminescence, which appeared to be a legacy associated with their manufacturing history and the partial oxidation of their structures, which gave peroxide functionalities. This was more notable for the complex antioxidant structures. Under oxygen, higher levels of chemiluminescence were observed, and this was indicative of some level of oxidation associated with the antioxidant structures. With temperature‐ramping experiments, the chemiluminescence emission was significant and only observed at temperatures close to the melting points of the additives and/or polymer. Mobility was clearly an essential feature of this reaction emission because chemiluminescence was well observed when the molten state was reached. Under normal practical conditions, such levels of chemiluminescence, because of employed stabilizers, do not contribute significantly to the chemiluminescence emissions of stabilized polymer materials. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3312–3326, 2002     

"Green"-enzymatic synthesis of pegylated phenolic macromer and polymer

Environmentally benign synthesis of novel pegylated polyphenolics, by combining the extraordinary selectivities of a lipase and an oxidase to develop polymeric electrolytes for applications in dye sensitised solar cells.     

Structure of interpenetrating polymer networks

A possible model for the formation of interpenetrating polymer networks is suggested. Phase separation is assumed to be faster than gelation. This implies that domains rich in either component grow first until late stages of spinodal decomposition. In these domains, short linear chains are crosslinked, leading to large branched macromolecules. Growth of the domains is slowed down by the presence of crosslinked polymers. It is assumed that it is stopped when the sizes of the domains and of the branched macromolecules are comparable. The resulting domains are significantly larger than the average distance between crosslinks. These results are supported by recent neutron scattering results on a poly(carbonate-urethane)/polyvinyl pyridine interpenetrating network. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1507–1512, 1998     

Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions: engineering polymer beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.     

Structure of hydrated Na-Nafion polymer membranes

We use molecular dynamics simulations to investigate the structure of the hydrated Na-Nafion membranes. The membrane is "prepared" by starting with the Nafion chains placed on a cylinder having the water inside it. Minimizing the energy of the system leads to a filamentary hydrophilic domain whose structure depends on the degree of hydration. At 5 wt % water the system does not have enough water molecules to solvate all the ions that could be formed by the dissociation of the -SO3Na groups. As a result, the -SO3Na groups aggregate with the water to form very small droplets that do not join into a continuous phase. The size of the droplets is between 5 and 8 A. As the amount of water present in the membrane is increased, the membrane swells, and SO3Na has an increasing tendency to dissociate into ions. Furthermore, a transition to a percolating hydrophilic network is observed. In the percolating structure, the water forms irregular curvilinear channels branching in all directions. The typical dimension of the cross section of these channels is about 10-20 A. Calculated neutron scattering from the simulated system is in qualitative agreement with experiment. In all simulations, the pendant sulfonated perfluorovinyl side chains of the Nafion hug the walls of the hydrophilic channel, while the sulfonate groups point toward the center of the hydrophilic phase. The expulsion of the side chains from the hydrophilic domain is favored because it allows better interaction between the water molecules. We have also examined the probability of finding water molecules around the Na+ and the -SO3(-) ions as well as the probability of finding other water molecules next to a given water molecule. These probabilities are much broader than those found in bulk water or for one ion in bulk water (calculated with the potentials used in the present simulation). This is due to the highly inhomogeneous nature of the material contained in the small hydrophilic pores.     

Structure formation in polymer blend solutions

Development of phase-separated morphologies has been studied in polymer blend solutions and forced mixtures of highly immiscible polymers by optical microscopy, DSC and light scattering. Unmixing was induced by different courses of solvent evaporation and by thermal agitation, respectively. Blends comprising different kinds of flexible and rigid chain molecules display various phase patterns in the late stage of phase decomposition which can be characterized roughly as being either regularly bicontinuous or irregularly shaped. Effects of polymer-polymer interaction and the blending ratio are discussed. Generally, evolution of morphologies depends on both internal parameters of the system and externally imposed unmixing conditions. Limits of percolating morphologies in the course of phase separation can be established qualitatively.     

Structure of polymer fluids in colloidal dispersions

We have calculated some structural properties of a fluid of hard sphere polymer chains about a variable sized central hard sphere with the Monte Carlo method in the canonical ensemble. We have additionally calculated these structural properties with an integral equation based on density functional theory. The integral equation theory gives good agreement with the simulations at all but the highest densities.     

Structure and aggregation of a helix-forming polymer

We have studied the competition between helix formation and aggregation for a simple polymer model. We present simulation results for a system of two such polymers, examining the potential of mean force, the balance between intermolecular and intramolecular interactions, and the promotion or disruption of secondary structure brought on by the proximity of the two molecules. In particular, we demonstrate that proximity between two such molecules can stabilize secondary structure. However, for this model, observed secondary structure is not stable enough to prevent collapse of the system into an unstructured globule.