Brønsted base mediated one-pot synthesis of catechol-ended amphiphilic polysarcosine-b-poly(N-butyl glycine) diblock copolypeptoids

Catechol moiety offers a versatile platform in the preparation of functionalized polymers, but it is not usually compatible with catalysis in polymerizations. To address these challenges, we suggest employment of one Brønsted base in masking the activity of catechol moiety and to modulate the polymerization. Based on this strategy, the ring-opening polymerization (ROP) of sarcosine N-carboxyanhydrides (Sar-NCA) was carried out using dopamine hydrochloride as an initiator and triethylamine as a Brønsted base. PSar with predicted molecular weights (M n,NMR=3.7 kg mol−1) and narrow dispersities (Đ<1.13) was prepared. Catechol initiator was successfully linked to PSar end as confirmed by MALDI-ToF MS. Subsequently, copolymerization of N-butyl glycine N-carboxyanhydrides (Bu-Gly-NCA) from the PSar in one-pot produced catechol end-functionalized amphiphilic polysarcosine-block-poly(N-butyl glycine) diblock copolypeptoids (cat-PSar-b-PGlyBu). Further, cat-PSar-b-PGlyBu enabled the aqueous dispersion of manganese oxide nanoparticles which was attributable to the anchor of the diblock copolymers onto the surface of the nanoparticles. The strategy for catechol masking and polymerization mediating by one Brønsted base offered a new avenue into the synthesis of catechol-ended block copolymers.

Metallic organophosphate catalyzed bulk ring-opening polymerization

Metallic organophosphates have catalyzed the bulk ring-opening polymerization of cyclic esters and cyclic carbonates through a bifunctional mode.

Organocatalyzed Anionic Ring-Opening Polymerizations of N-Sulfonyl Aziridines with Organic Superbases

The anionic ring-opening polymerizations (AROPs) of N-sulfonyl aziridines, in the presence of organic superbases including phosphazene (t-Bu-P₄), Verkade's base (P(i-PrNCH₂CH₂)₃N, TiPP), DBU, MTBD, and N,N,N',N'-tetramethylguanidine (TMG), using N-benzyl-p-toluenesulfonamide (BnN(H)Ts) as initiator were explored to produce metal-free poly(sulfonylaziridine)s. Among the superbases used, the catalytic activity was found directly proportional to their basicity. Remarkably, t-Bu-P₄ and TiPP gave a living/controlled AROP of 2-methyl-N-tosylaziridine (TsMAz), where t-Bu-P₄ performed better, affording the metal-free and well-defined poly(sulfonylaziridine)s with high molar masses (M_n(SEC) > 30 kg mol^-1) and low dispersities (Đ < 1.10) in 3.5 h. For the less reactive monomers of 2-methyl-N-ethylsulfonyl aziridine (EsMAz) and 2-phenyl-N-tosylaziridine (TsPhAz), t-Bu-P₄ showed the same excellent catalytic efficiency (30 equiv, conv. > 95%, 5 h). The organocatalyzed AROP allowed the use of lower catalyst (t-Bu-P₄) loading than the amount of initiator (BnN(H)Ts), but the propagating polymer chains were as many as the number of equivalents of the introduced initiators, which could lower the loading of catalyst used to amounts as low as 0.05 mol %.

Amphiphilic star-shaped poly(sarcosine)-block-poly(ε-caprolactone) diblock copolymers: one-pot synthesis, characterization, and solution properties

We firstly synthesized amphiphilic three-armed star-shaped poly(sarcosine)-block-poly(ε-caprolactone) diblock copolymers (s-PSar-b-PCLs), and investigated the solution properties and biocompatibility of the copolymers.

The effect of varying doses of oral iodized oil in the prophylaxis of endemic goitre in elementary schools children

The effect of oral iodine supplementation on total goitre rate (%TGR) and urinary iodine excretion among school children 4 to 16 years of age was studied. In the first group (n = 57) 200mg oral iodized oil reduced %TGR from 31.6% to 17.5% and 33.3% to 24.6% in males and females respectively, while in the second group (n = 53), 400mg iodine reduced the %TGR from 34.0% to 20.8% in males and 35.9% to 24.5% in females after 13 months of intervention. This gave a relative indication that the 200mg is as effective as the 400mg in goitre reduction. In subsequent tests, the maximum urinary iodine excretion was obtained from the groups which received two doses of iodized oil 24 hours after the intervention. A significant (p = 0.003) greater increase in urinary iodine excretion was noted at 24 hours among both male and female children administered 400mg than among those who received 200mg. Measurements after 24 hours showed no significant difference between urinary iodine excretion of the two dose groups. These results suggest that: (i) 200mg is likely equally effective as 400mg for iodine deficiency disorders control and prevention among children and (ii) iodine could be administered annually rather than biannually.

Interrelationship between vitamin A, iodine and iron status in schoolchildren in Shoa Region, central Ethiopia

A total of 14,740 schoolchildren in seven provinces of Shoa Administrative Region in Central Ethiopia were surveyed for the prevalence of goitre, xerophthalmia and anaemia. Haemoglobin and packed cell volume were assessed in 966 children in one province while an in-depth study was conducted on 344 children in the same province and two others. Goitre, xerophthalmia (Bitot's spots) and clinical anaemia were observed in 34.2, 0.91 and 18.6% respectively of the children. Most biochemical variables were within the normal range while those of haemoglobin (Hb), mean corpuscular Hb concentration (MCHC) and urinary I excretion were lower, and mean corpuscular volume, mean corpuscular Hb (MCH), and immunoglobulins G and M were higher. Hb was strongly correlated with retinol, ferritin, MCHC, MCH, packed cell volume and erythrocyte count while retinol formed a triad with transthyretin (TTR) and retinol-binding protein (RBP) which were all correlated with one another. Total and free thyroxin and total and free triiodothyronine were positively correlated as were the concentrations of the total and free hormones. Thyrotropin (TSH) was negatively correlated with total and free thyroxin and positively correlated with free triiodothyronine. Thyroxin and triiodothyronine in both free and combined forms were all correlated with thyroxin-binding globulin which in turn was negatively correlated with the triad retinol, RBP and TTR. The triad was also negatively correlated with C-reactive protein. Urinary I excretion was positively associated with total thyroxin and negatively associated with TSH. The anaemia found was not nutritional in origin but due to the effect of infestation with intestinal parasites and malaria.

Severe vitamin A deficiency in a rural village in the Hararge region of Ethiopia

A total of 240 children were examined for vitamin A deficiency in a village in Hararge region of Ethiopia. Night blindness, Bitot's spots, corneal xerosis, corneal ulceration and corneal scars were observed in 69, 16, 2, 15 and 14 children, respectively, based on the most severe eye signs. Blood was collected from 76 children with eye signs and 9 other children selected at random. The concentration of retinol (vitamin A) in serum was < 0.35 mumol/l in 30.2% of children and the median serum retinol-binding protein, iron, transferrin saturation and ferritin levels were low while the parameters of iodine status, total triiodothyronine, total thyroxine and thyrotropin, were all within the normal range. Levels of IgG and IgM were elevated in 78.8% and 82.4% children, respectively, while C-reactive protein levels were elevated in 42.4% of children. There was a higher prevalence of wasting (33%) than stunting (10%) with an additional 8% of children being both stunted and wasted. In the 2 years prior to the study, there were 74 deaths of which 17 were reported to be associated with ruptured corneas. The community had been dependent on relief food aid for the previous 6 years.