Hydrophilic/hydrophobic copolymers units

Methacrylates with pendant oxyethylene units (FM-19) were polymerized in a controlled way with metal catalysts in the bulk or in water. The catalytic systems include a bromide initiator coupled with Ni-2 for n = 2 (bulk, 80 °C)319 and CuCl for n = 7-8.246-320 The latter polymerization proceeded very fast in aqueous media at 20 °C to reach 95% conversion in 30 min and gave very narrow MWDs (MJMn =1.1 — 1.3). The fast reaction is attributed to the formation of a highly active, monomeric copper species com-plexed by the oxyethylene units. A statistical copolymerization of FM-19 (n = 7—8) and FM-20, a methacrylate with a oligo (propylene oxide) pendant group, led to hydrophilic/hydrophobic copolymers with narrow MWDs (MwIMn = 1.2).320... 

Fig. 24 The side-chain models of amphiphilic polymers a amphiphilic homopolymer (poly-A), b regular alternating HA copolymer, c regular multiblock HA copolymer, and d protein-like HA copolymer. Each hydrophobic monomer unit (H) is considered as a single interaction site (bead) each amphiphilic group (A) is modeled by a dumbbell consisting of hydrophobic (H) and hydrophilic (P) beads...

Fig. 2 Schematic representation of a the HP model and b the dumbbell HA model of an amphiphilic copolymer. P-units are hydrophilic (polar), H-units are hydrophobic, and A-units are amphiphilic. (Adapted from Ref. [25])...

The copolymerization of species having hydrophilic side groups with hydrophobic monomer units has led to the development of water-dispersible coatings of considerable promise. The morphology of these polymers and the orientation that takes place at the interface are of particular importance, for organic cosolvents are used in the copolymer synthesis and also as solubilizers. 

Abstract Protein-like copolymers were first predicted by computer-aided biomimetic design. These copolymers consist of comonomer units of differing hydrophilicity/hydrophobicity. Heterogeneous blockiness, inherent in such copolymers, promotes chain folding with the formation of specific spatial packing a dense core consisting of hydrophobic units and a polar shell formed by hydrophilic units. This review discusses the approaches, those that have already been described and potential approaches to the chemical synthesis of protein-like copolymers. These approaches are based on the use of macromolecular precursors as well as the appropriate monomers. In addition, some specific physicochemical properties of protein like copolymers, especially their solution behaviour in aqueous media, are considered. 

Nafion membranes are composed of hydrophobic-hydrophilic comonomers. When the ionic form of Nafion is exposed to water, some swelling takes place. However, in order to minimize the free energy of the system, water will be taken up in such a way as to avoid contact with the hydrophobic TFE units of the copolymer. At equilibrium, for a fixed structure, there will be a balance between the free energy of dilution (osmotic swelling) and the free energy of hydration of the TFE units. As a result of these two opposing effects, water of hydration is contained in ion clusters which reduces the necessity of water-TFE interaction and yields a system of minimum energy. Several models... 

More recently, block copolymers with sequenced hydrophilic and hydrophobic units have been developed for the sulfonated poly (arylene ether)s with rather low lEC to show high proton conductivity [5, 6]. They have better-developed hydrophilic/hydrophobic nanophase separation and, accordingly, better-connected ionic channels compared to the conventional random copolymers of the same chemical structure and composition. A typical and well-examined example is block copolymers composed of biphenol-based disulfonated arylene ether sulfone (the so-called BPSH) units and the unsulfonated equivalents (BPS) (Fig. 1) by McGrath s group [7-9]. They have investigated detailed properties of the BPSH block copolymer membranes to obtain the following informative conclusions ... 

With nanoparticles, the architectnre of the particle shell or matrix can be formulated and fine-tuned to offer controlled release of its contents, ranging from constant but prolonged release to zero release. The particles can be formulated with desired characteristics via key structural features, such as CToss-tmking density, hydrophilic-hydrophobic balance of the copolymer units, and stiffness of the polymeric network. Furthermore, erodible or biodegradable particles can be used to combine the release mechanisms of diffusion and erosion. In addition, the particles can be designed to respond to different stimuh from the external environment by adjusting a number of parameters, such as pH, temperature, ionic strength, cosolvent composition, pressure, or electric field. 

---