Amphiphilic copolymers analysis

Nuclear magnetic resonance monitoring of the synthesis of amphiphilic copolymers has also been reported by Larazz et al. [174] for the copolymerization of a methacrylic macromonomer with amphiphilic character derived from Triton X-100 (MT) with acrylic acid (AA). In situ H NMR analysis was used to monitor comonomer consumption throughout the copolymerization reactions, initiated by AIBN in deuterated dioxane, at 60 °C. The results from two different approaches used by the authors to estimate the reactivity ratio of the macromonomer indicate that AA is less reactive than the macromonomer MT and a model monomer with lower molecular weight but same structure, suggesting that methacrylic double bond reactivity was not affected by poly(oxyethylene oxide) chain length. 

Three arm amphiphilic star block copolymers of IBVE and 2-hydroxyethyl vinyl ether (HOVE) were prepared using the trifunctional initiator 8 with sequential cationic polymerization of two hydrophobic monomers, IBVE and AcOVE. Subsequent hydrolysis of the acetates led to the hydrophilic poly(HOVE) segments [38]. Two types of stars were prepared depending on which monomer was polymerized first three arm star poly(IBVE-h-HOVE), with the hydrophobic part inside and three arm star poly(HOVE-h-IBVE), with the hydrophobic part outside. When IBVE was polymerized first, the experimental conditions were the same as described in Sect. 2.2.1. After reaching quantitative monomer conversion, AcOVE was added and temperature was raised from 0 to 40 °C to accelerate the reaction since this monomer is less reactive than IBVE. When starting with AcOVE as a first block, both polymerizations were carried out at 40 °C. SEC analysis showed that MWDs were narrow for the two steps whatever the se-... 

Such hydrophilic macromonomers (DPn=7-9) were radically homopolymer-ized and copolymerized with styrene [78] using AIBN as an initiator at 60 °C in deuterated DMSO in order to follow the kinetics directly by NMR analysis. The macromonomer was found to be less reactive than styrene (rM=0.9 for the macromonomer and rs=1.3 for styrene). Polymerization led to amphiphilic graft copolymers with a polystyrene backbone and poly(vinyl alcohol) branches. The hydrophilic macromonomer was also used in emulsion polymerization and copolymerized onto seed polystyrene particles in order to incorporate it at the interface. 

Yui s group analyzed the thermodynamics on the inclusion complexation between the a-cyclodextrin-based nanotube and sodium alkyl sulfonate [148]. They prepared a supramolecular hydrogel utilizing enthalpy-driven complexation between the molecular tube and an amphiphilic molecule [147]. They carried out the thermodynamic analysis of inclusion complexation between a-cyclodextrin-based molecular tube and poly(ethylene oxide)-Wocfc-poly(tetrahydrofuran)-b/oc/c-poly(ethylene oxide) triblock copolymer in terms of isothermal titration calorimetry [157]. Furthermore, they incorporated the tube into gels that could recognize the length of alkyl chain [158]. 

Kubisa et al. also used hydroxy-functional PEG after reaction with 2-bromo-propionyl bromide as an ATRP macroinitiator [228]. Their goal, however, was to polymerize ferf-butyl acrylate, rather than St, then to hydrolyze the esters to acid functionality and study the cation binding properties of the doubly amphiphilic block copolymers. They utilized a CuBr/PMDETA catalyst system for the polymerization and, although the macroinitiator was completely consumed, MALDI-TOF analysis indicated that bromine was replaced with a hydrogen at... 

Essential details of four graft copolymer samples (25a-25d) thus obtained are given in Table 11. The samples have been briefly examined by sedimentation equilibrium analysis. The molecular weights (M ) obtained by this method are consistent with, but lower than, the expected values recorded in Table 11. Another series of amphiphilic graft copolymers with a double comb structure has also been synthesized (26, in Fig. 19) [47]. Similarly, type 27 graft copolymers have been prepared by the reaction of the activated copolymer with hydroxy-terminated polyurethanes, but these have not so far been characterized. 

A number of theoretical studies have been devoted to analysis of the self-assembly of amphiphilic ionic/hydrophobic diblock copolymers [13-24]. Most of these studies considered copolymers with strongly dissociating (also referred to as quenched ) PE blocks [13-18, 20] and extensively exploited the analogy between the conformation of PE blocks in a corona and that in a spherical PE brush [25-33] or PE stars (see [10] for a review). The micellization and the responsive behavior of nanostructures formed by copolymers with pH-sensitive PE blocks have also been systematically studied in recent years [19, 21-23]. 

The general principles of self-assembly of amphiphilic molecules into finite-sized aggregates (micelles) are described in a number of classic books [34-36]. In our analysis of micelle formation we apply the equilibrium close association model. That is, we assume first that only one population of micelles, with an aggregation number p (number of copolymers in one aggregate), is present in the system at any given concentration of amphiphiles in the solution, or that there are no micelles at all and second, that the free energy per molecule in a micelle, Fp, exhibits a minimum at a certain value of the aggregation number, p = po. 

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