A sample of triblock copoly(oxyethylene/oxypropylene/oxyethylene) Synperonic F127 was purified. The micellisation and gelation properties of aqueous solutions of purified and unpurified copolymers were investigated by surface tension measurement, static and dynamic light scattering, differential scanning calorimetry and NMR spectroscopy. Generally, the results obtained for the two samples were similar: an exception was the surface tension. Endothermic standard enthalpies of micellisation were obtained over a wide concentration range, with corresponding endothermic standard enthalpies of gelation in the high concentration range. Considered on an equivalent basis, i.e. kJ mol-'(chains), gelation was found to be an almost athermal process compared to micellisation. Based on the presented evidence, particularly that from DSC, and considering other recent studies, it was concluded that the thermal gelation of F127 (i.e. gelation on raising the temperature) resulted essentially from the packing of spherical micelles. A small thermal event at the gelation point was ascribed to a disorder-order discontinuity.Block copolyethers composed of hydrophobic poly(oxypr0-pylene) (POP) and hydrophilic poly(oxyethy1ene) (POE) are non-ionic surface-active agents with a wide range of application. The most used commercial copolymers are triblocks : i.e. H[OCH,CH,],[OCH2CH(CH3)]n[OCH2CH2]mHor E,P,E, Variation of the ratio of oxyethylene to oxypropylene (rn : n) and the number of units in each block (i.e. the overall chain length, x = 2m + n) allows the properties of the block copolymers to be varied in a controlled way.The association properties of triblock copolymer F 127 in aqueous solution have attracted much research interest, not least because of the interesting thermally reversible gelation of its concentrated solutions. 'J According to the published grid,' F127 has the formula E1,$&1,6, where E represents an oxyethylene unit and P an oxypropylene unit. The micellisation of F127 in dilute aqueous solution has been studied p r e v i o~s l y ,~-~ as have the solubilisation properties of its micellar solutions.' The gelation properties of concentrated solutions of F127 have been studied more ~f t e n , ' ,~,~,~-'~ particularly with regard to application in controlled-drug-release systems. Detailed studies of micellisation and micellar solutions by Attwood et ~1 . ~7~ and by Wanka et a[.' reveal some divergence of quoted results: e.g. at 25 "C ref. 3, 4 ref. 5 critical micelle concentration aggregation number ca. 15 ca. 30 (c.m.c.)/g dm-1 0.04In part, these differences reflect a different choice of experimental methods and interpretation of results. A significant consideration, pointed out by Attwood et aI.,12 is the variability of the properties of different batches of F127 (and related copolymers) resulting from variation in their molecular composition. Apart from the natural width of the composition distribution, triblock copolyethers may contain diblock copolymers originating from the transfer reaction in the anionic polymerisat...
SUMMARYIn two children with atopic dermatitis, routine vaccination with bacillus Calmette-Guerin (BCG) was followed by severe exacerbation of skin disease. If the sequence is cause and effect, a possible mechanism is stimulation of a Th2 lymphocyte cytokine profile by the vaccine, with migration of activated lymphocytes to inflamed skin. In children with active atopic dermatitis, BCG vaccination is best deferred until remission.The University Department of Child Health at Booth Hall Children's Hospital in Manchester has a special interest in atopic dermatitis (AD). Approximately 250 new patients per year are seen in the setting of a paediatric rather than a dermatology service. The patients are followed up until they improve, and the unit operates a drop-in service to deal with acute exacerbations. One complication that has been noted in this clinic is worsening of skin lesions after bacillus Calmette-Guerin (BCG) vaccination in teenagers with atopic dermatitis. Since the association between worsening of atopic dermatitis and BCG vaccination is not well known, we report two cases. CASE HISTORIESCase I Atopic dermatitis was first noted in this boy at the age of 6 weeks, and was regarded as a reason for withholding both pertussis and measles immunizations. He was under the care of a dermatologist from the age of 1 year, and he required admission to hospital for his dermatitis at the ages of 4, 5 and 10 years (the last admission shortly after referral to our service). Orchidopexy and a right inguinal hernia repair were performed at 1 1 1Y2 years of age. At that time, the skin lesions were confined to the hands, feet, face and chest wall, and were well controlled with Vioform Hydrocortisone ointment (1% hydrocortisone and clioquinol 3%) to the face and mildly affected areas, and Locoid C ointment (hydrocortisone butyrate 0. 1% and chlorquinaldol 3%) on more severe lesions.At 1134 years, BCG was administered to the left arm as part of a routine immunization schedule at school. A week later, eczema flared at the face, wrist and popliteal fossae. Despite treatment with oral flucloxacillin and the above topical steroids, the skin lesions continued to deteriorate and the patient was admitted to hospital 4 weeks after BCG vaccination. On admission, there were widespread severely inflamed skin lesions affecting the face, trunk and limbs, and the patient was very distressed. There was slight improvement with the use of a very potent steroid ointment (clobetasol propionate 0.05%). On the advice of the infectious disease service-because of concern about the possibility of disseminated BCG infection-he was treated for 3 months with isoniazid (6 mg/kg/day) and pyridoxine (10 mg daily). The exacerbation of the skin lesions resolved 31 months after vaccination. He was followed up in the clinic to the age of 14 years, by which time his skin lesions were mild and he was discharged. His case was reported to the Committee on Safety of Medicines.Case 2 Atopic dermatitis was first noted in this girl at the age of 10 months. An egg and ...
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