Hydrophobic poly segments

Historically, after the development of oligopeptide-based vesicles, several groups developed and characterized vesicles using polypeptide hybrid systems consisting of polypeptide and synthetic polymer blocks [17-19]. Soon thereafter, vesicles formed entirely from polypeptides, such as poly(L-lysine)-h-poly(L-leucine) and poly(L-lysine)-h-poly(L-glutamate), were developed [20, 21]. This review will focus on recent developments in the formation of vesicles composed of polypeptide hybrid or polypeptide systems, as well as the potential promise of these systems as effective dmg delivery vehicles. A specific example of a polypeptide-based vesicle is shown in Fig. 1, where the hydrophobic segment is a-helical and the hydrophilic segment is a random coil. 

Fig. 1 Vesicle construct formed from poly(L-lysine)-i)-poly(L-leucme) polypeptides where the poly(L-leucine) block corresponds to the a-helical hydrophobic segments and the poly (L-lysine) block corresponds to the random coil hydrophilic segments. Note that this is one specific example and not all vesicle constructs have a-helical and random coil blocks. Moreover, the amphiphilic copolymer can be comprised of either a pure block copolypeptide or a macromolecule consisting of a polypeptide and another type of polymer. Adapted from [20] with permission. Copyright 2010 American Chemical Society...

Hard contact lenses are composed of a polymer that repels water because the constituent repeating units (the monomers that link together to form the polymer) are nonpolar, hydrophobic segments. The first hard contact lens was constructed in 1948 from the monomer known as methyl methacrylate (MMA), yielding the polymer poly(methyl methacrylate) or PMMA. This material offers durability, optical transparency, and acceptable wettability for optimal comfort. Today the rigid lens material of hard contact lenses is often constructed by combining MMA with one or more additional hydrophobic monomers to provide better gas permeability. 

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-... 

Block copolymers that consist of hydrophilic and hydrophobic segments are typical amphiphilic polymers, a variety of which have been synthesized by living cationic polymerization. Figure 9 schematically illustrates the structures of some of these amphiphilic polymers thus far obtained though the examples therein are based on poly(vinyl ether) segments, any other appropriate segments may be incorporated. As seen in the illustrations, macromolecular amphiphiles are not necessarily linear AB- and ABA-type block copolymers but may be graft, multiarmed, and network polymers, where the basic components are amphiphilic block copolymers. 

Recognition of the Hydrophobic Segment Lengths of Poly(bola-amphiphile)s... 

Polymers can also form gels, such as gelatin, as a solid suspension. Entangled polymer chains trap solvent. Some polymer mixtures form solid-insolid solutions, such as poly(ethylene) and poly(propylene) blends in clothing fabrics. Polymers can also be surfactants, such as starch with hydrophilic and hydrophobic segments. 

The conventional free radical copolymerization of 3-pinene and MMA or St, initiated by AIBN, yielded copolymers with Mw of about 11 600 and 25 400, respectively and MWD of 1.5 and 1.7, respectively [56]. When 2,3,4,5,6-pentafluorostyrene (PFS) was used as comonomer, and benzoyl peroxide as the initiator, a PFS-rich copolymer incorporating isolated isomerized 3-pinene units distributed between poly(PFS) segments was obtained [57]. This feature is related to the low reactivity of the 3-pinene free radicalar towards its monomer, that is to a reactivity ratio close to zero. These PFS-[3-pinene copol5miers were shown to combine the typical high water contact angles of perflourinated polymers (hydrophobicity) with the optical activity of polyOPESf) [57]. A recently published study indicated that the radical random copolymerization of both a- and 3-pinene with styrene under microwave irradiation yields materials with Mn values considerably higher than those obtained under conventional conditions, but still with very low conversions [18]. 

We have focused on the design of multistimuli-responsive nanoparticles using a mixture of block copolymers having a common temperature-responsive segment. The shell-mixed nanoparticles (shell poly(N-isopropylacrylamide) (poly(NIPAAm)) and PEO segments) have been prepared via hydrophobic-hydrophobic interaction [44], stereocomplex interaction [45], and electrostatic interaction [46]. We used the temperature-responsive poly(NIPAAm) segment for the shell-mixed nanoparticles. Poly(NIPAAm)-fo-poly(NIPAAm-co-HMAAm)s... 

---