Christian V. Nicholas

Effect of chain length on the micellization and gelation of block copoly(oxyethylene/oxybutylene/oxyethylene) EmBnEm

Abstract Three triblock copoly(oxybutylene/oxyethylene)s, E 58 B 17 E 58 , E 71 B 28 E 71 and E 132 B 53 E 132 , with similar composition (75–80 wt% E) but different chain lengths, were prepared by sequential anionic copolymerization, and their micellar and gelation properties in aqueous solution were determined. The methods used were light scattering intensity, photon correlation spectroscopy and gel permeation chromatography, together with observation of gelation. Measurements were made at 30°C over the full concentration range from dilute solution into the gel. The lower and upper temperature boundaries of the gel regions were identified. Phase separation was observed in dilute solutions of the copolymer of longest chain length (E 132 B 53 E 132 ). Critical micelle and gel concentrations decreased markedly as chain length was increased, and micellar weights and sizes increased.

Micellisation and gelation of block-copoly(oxyethylene/oxybutylene/oxyethylene) E58 B17 E58

A triblock-copoly(oxybutylene/oxyethylene), denoted E58 B17 E58 (80 wt-% E), was prepared by sequential anionic copolymerisation and its micellar and gelation properties in aqueous solution were determined. The oxybutylene/oxyethylene copolymer had the advantage over comparable oxypropylene/oxyethylene copolymers of greater uniformity of composition and chain length. The methods generally used were surface tension, light scattering intensity, photon correlation spectroscopy, together with observation of gelation. Measurements were made at 30°, 40° and 55° C over a full concentration range from dilute solution into the gel (>200 g dm−3) and at specified concentrations, including the gel, over the temperature range from 10° to 70° C. The lower and upper temperature boundaries of the gel region were identified, and the occurrence of syneresis was noted. The properties investigated and discussed include critical micelle and gel concentrations, micellar weights and sizes, and structures and mobilities in the gel.

BLOCK-COPOLY(OXYETHYLENE/OXYBUTYLENE/OXYETHYLENE), E40B15E40, IN AQUEOUS SOLUTION : MICELLISATION, GELATION AND DRUG RELEASE

Triblock copoly(oxyethylene/oxybutylene/oxyethylene) E40B15E40 was prepared by sequential anionic copolymerisation and its micellar, gelation and drug release properties in aqueous solution were investigated. The gel region of the temperature–concentration diagram was identified, including the lower and upper temperature gel–sol boundaries. Static and dynamic light scattering measurements were made on solutions at 20.5–22.5, 37 and 65 °C over a wide concentration range from dilute solution into the gel range (>230 g kg–1) and at high concentration, including the gel phase, over the temperature range from 20.5 to 70 °C. A brief investigation of the rate of release of salicyclic acid from the gel served to illustrate useful sustained release. The gelation behaviour, interpreted via the hard-sphere model, was consistent with the measured micellar sizes.

Micellisation and gelation of triblock copolymer of ethylene oxide and ε-caprolactone, CLnEmCLn, in aqueous solution

Three triblock copolymers of ethylene oxide and Iµ-caprolactone, nominally CL2E90CL2, CL4E90CL4 and CL6E90CL6 have been prepared and characterised. The micellar and surface properties in aqueous solution of the copolymers with CL-block lengths of four and six were investigated as a function of temperature and concentration using surface tension and static and dynamic light scattering techniques. Reversible gelation on cooling solutions of CL6E90CL6 was observed at critical concentrations and temperatures ranging from 130 g kg–1 at 25 °C to 300 g kg–1, at 80 °C.

Polymer electrolytes formed from oxymethylene-linked poly(oxyethylene) and alkali metal perchlorates studied by Raman spectroscopy

Abstract Raman spectra were recorded for mixtures of oxymethylene-linked poly (oxyethylene), poly [oxymethylene-oligo (oxyethylene)], with sodium and lithium perchlorate in various molar ratios. The effect of salt concentration on the bands at 250–310 cm −1 and ca. 860 cm −1 is discussed.

High-molar-mass branched poly[oxymethylene-oligo(oxyethylene)] for use in polymer electrolytes

High-molar-mass poly[oxymethylene-oligo(oxyethylene)](POMOE, oxymethylene-linked PEG400) was prepared by inclusion of a multifunctional alcohol in the polycondensation recipe. Approximate values of the critical concentration for gelation were determined. Branching in samples prepared at lower-than-critical concentrations was confirmed by comparison of molar masses determined by gel-permeation chromatography and static light scattering. Melt flow indices confirmed an increase in viscosity. Differential scanning calorimetry and dynamic mechanical thermal analysis were used to determine glass-transition and melting temperatures of the polymers and of mixtures of the polymers with lithium perchlorate. Conductivities of polymer–salt mixtures were measured. Comparison of results for branched and linear polymers indicated no significant difference in properties, including conductivity, apart from a decrease in melt flow index.