Linear method for determining monomer reactivity ratios in copolymerization

The average configuration of polymer molecules in solution is markedly influenced by the obvious requirement, ordinarily disregarded in problems relating to molecular configuration, that two elements of the molecule are forbidden from occupying the same location in space. The influence of spatial ``interferences'' between different segments of the molecule on its average configuration has been investigated by statistical and thermodynamic methods.It is shown that if the average linear dimension of a polymer chain is to be taken proportional to a power of the chain length, that power must be greater than the value 0.50 previously deduced in the conventional ``random flight'' treatment of molecular configuration. This power should approach 0.60 for long chain molecules in good solvents. With increase in size of the solvent molecule, the influence of interference on molecular configuration diminishes, vanishing entirely in the extreme case of a solvent which is also a high polymer. The effect of a heat of in...

The Configuration of Real Polymer Chains

Zwitterionic materials have moieties possessing cationic and anionic groups. This molecular structure leads to unique properties that can be the solutions of various application problems. A typical example is that zwitterionic carboxybetaine (CB) and sulfobetaine (SB) materials resist nonspecific protein adsorption in complex media. Considering the vast number of cationic and anionic groups in the current chemical inventory, there are many possible structural variations of zwitterionic materials. The diversified structures provide the possibility to achieve many desired properties and urge a better understanding of zwitterionic materials to provide design principles. Molecular simulations and modeling are a versatile tool to understand the structure–property relationships of materials at the molecular level. This progress report summarizes recent simulation and modeling studies addressing two fundamental questions regarding zwitterionic materials and their applications as biomaterials. First, what are the differences between zwitterionic and nonionic materials? Second, what are the differences among zwitterionic materials? This report also demonstrates a molecular design of new protein-resistant zwitterionic moieties beyond conventional CB and SB based on design principles developed from these simulation studies.

Molecular Understanding and Design of Zwitterionic Materials

The configurational entropy of a mixture of solvent and polymer molecules composed of segments connected by flexible bonds has been derived for the case in which the lattice they occupy contains limited regions of perfect order (i.e., the crystallites), which are reserved for occupancy by polymer segments exclusively. Although the derivation is carried out primarily for polymer chains of uniform length, modifications required for the treatment of heterogeneous polymers are included. An expression for the free energy of fusion ΔFf of the semicrystalline mixture of polymer and solvent is derived assuming a vanLaar heat of mixing term.The equilibrium (average) crystallite length ζe, derived by differentiation of ΔFf, depends principally on the ``nucleation parameter'' D which, though it evades explicit evaluation from theory, represents the relative ease with which the first layer of a crystallite tends to form; ζe may depend to a lesser extent on the degree of crystallinity. The equilibrium degree of crysta...

Thermodynamics of Crystallization in High Polymers. IV. A Theory of Crystalline States and Fusion in Polymers, Copolymers, and Their Mixtures with Diluents

Water-soluble (co)polymers represent a diverse class of macromolecules ranging from naturally occurring biopolymers such as polysaccharides and most polypeptides to wholly man-made materials. Such materials have found a wide-range of applications. In this article we detail the synthesis and solution characteristics of both natural and synthetic polymers. Emphasis is placed on polynucleotides, polypeptides, and polysaccharides for naturally occurring polymers, while the discussion regarding synthetic materials is divided into sections dealing with neutral, anionic, cationic, and zwitterionic species. Special attention is given to recent advances in synthetic methodologies which now allow the tailoring of synthetic materials with precisely controlled microstructures, predetermined molecular weights, narrow molecular weight distributions, and complex topologies.



Finally, we detail some of the self-assembly characteristics of both high molecular weight statistical copolymers and lower molecular weight block copolymers in aqueous media with an emphasis on those materials which undergo phase transitions and/or conformational changes in response to an applied stimulus.


Keywords:

water-soluble polymers;
naturally occurring polymers;
polynucleotides;
polypeptides;
proteins;
polysaccharides;
nonionic polymers;
polyelectrolytes;
polyzwitterions;
polyampholytes;
polybetaines

Water-Soluble Polymers

Side Chain Crystallization of n-Alkyl Polymethacrylates and Polyacrylates1

Synthetic electrical analog of proteins1

The viscoelastic properties of plasticized Vinylite VYNW were studied over a wide range of time scale by means of the tensile creep test. A number of different plasticizers were compared as to their plasticizing effectiveness. It was found that different plasticizers imparted distinctly different shapes to the creep curve of the plasticized ferent plasticized resin. The flat creep curve, characteristic of trioctyl phosphate, is considered to be superior to the steep creep curve of tricresyl phosphate. Mixtures of plasticizers were also studied. A number of conjectures are advanced concerning the molecular mechanism of plasticizer action. One important characteristic of a plasticized formulation of the polyvinyl chloride types of resin is the existence of a three-dimensional gel structure of great permanence which prevents the occurrence of irrecoverable viscous flow.

Creep behavior of plasticized vinylite VYNW

1. The specific viscosity of a dilute solution of polystyrene or rubber is strongly dependent on the nature of the solvent; the specific viscosity is high in a good solvent, and low in a poor solvent or a solvent-nonsolvent mixture. This has been interpreted as being due to changes in mean molecular shape. The specific viscosities of cellulose acetate solutions are not so sensitive to the nature of the solvent. 2. The extrapolated specific viscosity at the limit of solubility is in the same range for several different solvent-nonsolvent systems. 3. The effect of a temperature increase is to lower the specific viscosity of rubber or polystyrene solutions in a good solvent, but to increase the specific viscosity in a mixture of solvent and nonsolvent. 4. The specific viscosity of a dilute polystyrene solution is more nearly linear with concentration in a toluene-methanol mixture than in pure methanol. The quadratic term b in the equation: (ηsp=ac+bc2), is reduced relatively more than the linear ter...

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions

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Papers

Side Chain Crystallization of n-Alkyl Polymethacrylates and Polyacrylates1

Synthetic electrical analog of proteins1

Creep behavior of plasticized vinylite VYNW

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions