This paper reports on the synthesis of dihydroxy terminated poly(chloroethyl vinyl ether)s (PCEVE) via bifunctional living cationic polymerization. The bifunctional chain initiator is obtained by reacting malonaldehyde bis(diethyl acetal) with trimethylsilyl iodide (TMSI) to form the corresponding di-α-iodo ether derivative. The polymerization of chloroethyl vinyl ether is then triggered by ZnCl_2. The direct transformation of active ends into aldehyde terminals, as well as their derivatization into hydroxy groups, is described. The synthesis of high molar mass ditelechelics by bifunctional polymerization provides evidence for the occurrence of a monofunctional side initiation. The latter has been attributed to the hydrolysis of TMSI by adventitious water, which leads to the in situ formation of hydrogen iodide. In order to trap hydrogen iodide, the influence of different additives, bulky amines, metals and alkylaluminiums, was investigated. Therefore, in the presence of alkylalumini-um, it is possible to obtain a clean bifunctional polymerization up to relatively high molar mass ditelechelic PCEVE (M_n = 33000 g/mol, M_w/M_n = 1.11).
Cermeno, Maria;Felix, Manuel;Connolly, Alan;Brennan, Elaine;Coffey, Bernadette;Ryan, Edel;FitzGerald, Richard J.
年/卷/期：2019 / 88 / Mar.
The conjugation of proteins with carbohydrates generates covalent bonds which may improve their techno- and biofunctional properties and therefore expand their applications in the food industry. In the present study, a design of experiments (DOE) approach was used to determine the effect of conjugation of whey protein concentrate (WPC) and WPC hydrolysates with carrageenan (CGN) on its emulsifying and antioxidant properties. The DOE was composed of 3 levels with 3 factors, i.e., WPC: CGN (1:1.0 1:3.5, 1:6.0), time of conjugation (6, 27 and 48 h) and degree of hydrolysis (DH; unhydrolysed, low DH and high DH). The conjugated samples were characterised for their oxygen radical absorbance capacity (ORAC) and emulsion activity (EA). Two samples, C3 (1:1.0, 6 h and unhydrolysed) and C4 (1:1.0, 6 h and low DH) with ORAC and EA values of 601.30 +/- 14.71 and 709.32 +/- 11.11 mu mol Trolox equivalents g(-1) freeze-dried powder and 0.51 +/- 0.01 and 0.58 +/- 0.01 absorbance units, respectively, were selected for further study. Emulsions were generated with WPC, non-conjugated (NC3 and NC4) and conjugated (C3 and C4) samples and their functional properties were compared. The NC3 and NC4 samples had higher viscoelastic moduli (G' and G '') than C3, C4 and the WPC samples which indicated that more stable emulsions may be formed with non-conjugated samples. However, the NC3, NC4 and WPC samples showed low emulsion stability (ES) after 28 days storage with values ranging from 78.6 +/- 3.5-85.6 +/- 3.6% whereas the conjugated C3 and C4 samples had improved ES with significantly (p < 0.05) lower coalescence index values (64.2 +/- 2.5 and 66.7 +/- 3.7%, respectively). However, conjugation of the hydrolysate (C4) had a significant (p < 0.05) negative effect on lipid oxidation (0.62 +/- 0.04 equivalents of 1,1,3,3-tetraethoxypropane (TEP)/kg emulsion) compared to the unhydrolysed conjugate C3 (0.42 +/- 0.04 eq TEP/kg emulsion).