Donald N. Schulz

Phase behaviour and solution properties of sulphobetaine polymers

Abstract Aqueous polyelectrolytes have been extensively studied and comprehensively described in numerous books and reviews. In contrast, systematic investigations of aqueous polyzwitterions are few. This paper describes the detailed phase behaviour and solution properties of a homopolymer based upon a recently available sulphobetaine monomer, N -(3-sulphopropyl)- N -methacrylooxyethyl- N , N -dimethyl ammonium betaine (SPE). In addition, such properties are probed at the molecular level by static and dynamic light scattering, as well as laser Raman spectroscopy. Poly[ N -(3-sulphopropyl)- N -methacrylooxyethyl- N , N -dimethyl ammonium betaine], P(SPE), of 4.35 × 10 5 M w shows remarkable phase behaviour. It exhibits both an upper critical solution temperature ( UCST ) and an ‘apparent inverted’ lower critical solution temperature ( LCST ), i.e. a 1-phase region flanked by two 2-phase regions. Moreover, the UCST occurs at an order of magnitude lower polymer concentration than predicted by theory or demonstrated by experiment with conventional polymers. The aqueous solubility of (SPE) depends upon polymer molecular weight, as well as the concentration and structure of added salts. ‘Soft’ salt anions and cations are more effective solubilizers than ‘hard’ anions and cations. Furthermore, solutions of P(SPE) display ‘antipolyelectrolyte behaviour’, i.e. viscosities which increase with increasing salt concentrations. Static light scattering experiments indicate that the solvent quality for P(SPE) increases with increasing salt concentration. Dynamic light scattering measurements show that the polymer diffusion coefficients decrease and the chain dimensions increase with increasing salt concentrations. Moreover, laser Raman spectroscopy indicates that the local environment around the zwitterion functionalities is also modified by changes in salt concentration. Based upon such molecular level probes, models have been proposed to account for the P(SPE) phase behaviour and solubility. Thus, P(SPE) is depicted as a collapsed coil in water because of intra-group and intra-chain associations. The unusual phase behaviour of P(SPE) in water is rationalized in terms of a shift from intra- to interinteractions. In turn, NaCl breaks up the intra-associations and promotes polymer solubility.

Copolymers of acrylamide and surfactant macromonomers: synthesis and solution properties

Abstract Surfactant macromonomers ‘surfomers’ have been copolymerized with acrylamide to form hydrophobically associating polymers. This study focuses upon the use of nonylphenoxypoly(etheroxy) acrylates of variable poly(etheroxy) chain length. Since such hydrophobic monomers have built in surfactant character, no external surfactant is needed for the preparation of high molecular weight acrylamide copolymers with 0.1–5 mol%, hydrophobe content. The acrylamide surfomer copolymers containing even small concentrations of surfomer (i.e. ⩽0.5 mol%) show interesting solution properties, e.g. enhanced viscosity above C∗ , and reduced viscosity below C∗ . The viscosity of such polymers is more sensitive to the surfomer level and type than to changes in [ M ] [ I ] 1 2 . Highest solution viscosities are achieved for polymers purified/isolated by a solution polymer route.

Rod to coil transition and aggregation in soluble polydiacetylenes: Semidilute regime

Visible absorption, rheological measurements, polarizing light microscopy, and temperature–time dependent quasielastic light scattering was used to examine the dilute–semidilute properties of polydiacetylene solutions, specifically poly(4BCMU). A good (tetrahydrofuran) and poor (toluene) solvent were selected for examining solution properties over a broad range of solvent quality. In this particular instance, poly(4BCMU) dissolved in both the pure solvents and their respective mixtures. Based on the observation that dramatic color changes (yellow–orange–red) can occur with the hydrodynamic radius remaining invariant, it is quite likely that the color changes are due to a local modification in the conjugation length. That is, on a molecular level, a local stiffening of the segments occurs as the magnitude of the red absorption component increases. Interestingly, the stability of the solutions towards aggregation/phase separation also correlates well with the absorbance value of the red peak. Furthermore, c...

Blends of amorphous-crystalline block copolymers with amorphous homopolymers. Morphological studies by electron microscopy and small angle scattering

A morphological study was performed with symmetric diblock ethylene-propylene copolymer (DEP) and the binary blends made from DEP and atactic polypropylene (APP) by use of small angle X-ray, light and neutron scattering, and also scanning and transmission electron microscopy. DEP contains a crystallizable polyethylene block and an amorphous atactic polypropylene block. Quenching the blends in liquid nitrogen preserved the morphology in the melt state. This quenching technique revealed that DEP forms a lamellar microdomain structure and blending DEP and APP includes morphological changes in the microdomain structures as well as macrophase separation. When the APP chain was shorter than the APP block, the addition of APP changed the morphology from a lamellar to a bicontinuous cylindrical and then a discrete cylindrical and finally to a spherical structure. On the other hand, when the APP chain was longer than the APP block, macrophase separation was observed and only a transition from a lamella to a bicontinuous cylinder occurred. These morphological transitions in the melt state can be correlated to differences in the crystallization kinetics of the blends.

Synthesis and properties of copolymers of ethylene/carbon monoxide with styrene/carbon monoxide

The terpolymerization of ethylene, styrene, and carbon monoxide was accomplished by two different palladium-based catalysts: a phosphine-based ligand system and a nitrogen-based ligand system. The range of possible compositions and the composition dependence of the properties of the resulting polymers were determined. These polymers were essentially carbon monoxide versions of the ethylene styrene interpolymers recently presented by Dow. A comparison between the two families of polymers is attempted.

Dynamic viscoelastic properties of poly(ethylene-propylene) diblock copolymer in the melt state and solutions

Abstract Dynamic mechanical properties of a symmetrical poly(ethylene-propylene) diblock copolymer with a molecular weight of 99 × 10 3 were investigated in the melt state, as well as in solutions in 1,2,4-trichlorobenzene. In the melt state, the frequency dependence of the elastic and loss moduli ( G ′ and G ″, respectively) exhibited a limiting behaviour of G ′ ≈ G ″ ≈ ω 0.5 in the terminal zone, a marker of inhomogeneity. Even solutions of 15 vol% polymer showed such inhomogeneity. These rheological data indicate that the diblock polymer is microphase separated and the phases are strongly segregated. The limiting behaviour in the terminal zone suggests that a lamellar structure is present in the melt.

Crystallization Kinetics and Microdomain Structures for Blends of Amorphous-Crystalline Block Copolymers with Amorphous Homopolymers

Blends of a symmetrical diblock poly(ethylene-b-propylene) (DEP) and an atactic polypropylene (APP) were studied by calorimetry, small angle neutron scattering, and electron microscopy. Addition of APP to DEP drastically changed the crystallization kinetics of the polyethylene block. The results were interpreted on the basis of the morphological studies of the microdomain structure in both the crystalline state and the melt state of the blends.

Thermodynamics of Random Copolymer Mixtures by Sans

A test of the theory of random copolymer miscibility is described in this paper. A series of random ethylene-butene copolymers were made by the saturation of polybutadienes of varying vinyl content, and the interactions in blends of these copolymers were measured by small angle neutron scattering (SANS). It was found that the standard random copolymer theory does not describe the data in that the interaction parameters were not proportional to the square of the difference in the compositions of the component copolymers. Rather, blends of ethylene rich copolymers had lower χ values than corresponding butene rich blends.

Functional Water Soluble Polymers

Functional polymers are macromolecules containing functional groups (e.g. -OH, -COOH, hydrophobes) which have polarity/reactivity differences from backbone chains. Alternatively, functional polymers may be viewed as materials that have a function or a use. Functional polymers often show unusual or improved properties by virtue of enhancements in phase separation, reactivity or associations.

Conformational Transitions in Polydiacetylene Solutions

Visible absorption, infrared absorption, Raman, and kinetic measurements are all strongly suggestive of a single-chain origin for the conformational transitions observed for polydiacetylenes in the solution phase, poly4BCMU and poly3BCMU being the prototypical examples. Intramolecular association between substituent groups on the polydiacetylene backbone has been assigned as the driving force for the transition; in the case of the BCMU polymers, hydrogen bonding provides the association mechanism. In this paper we review recent work on polydiacetylene solutions with emphasis on rheological and time-temperature dependent quasielastic light scattering measurements for poly4BCMU in the dilute-semidilute regime. Light scattering measurements during the coil-to-rod transformation (yellow-to-red color change) demonstrate that dramatic color changes take place without any measurable change in hydrodynamic radius, confirming the single-chain origin of the conformational change. On aging, aggregation is observed as an order-of-magnitude increase in hydrodynamic radius.