Precisely Defined Amphiphilic Graft Copolymers

Abstract

A family of precisely defined amphiphilic polyethylene-g-poly(ethylene glycol) copolymers has been synthesized using ADMET polycondensation chemistry. Altering the graft distribution and graft end group controls the morphology of the material: the polymers can be either semicrystalline or rendered completely amorphous. The precise monomer structures have been confirmed by 1H and 13C NMR, high-resolution mass spectrometry, and elemental analysis; the corresponding polymer structures have been confirmed by 1H and 13C NMR and FTIR. Melting temperatures can be controlled over a 60 °C range and glass transition temperature over 40 °C. Melting temperatures are incident with n-paraffin molecules having lengths similar to the static methylene sequence length between PEG branches. The observed thermal data are attributed to the crystallization of the polyethylene backbone, resulting in the exclusion of the PEG branches from the crystal, a result confirmed by X-ray diffraction.

Functionalized regio-regular linear polyethylenes from the ROMP of 3-substituted cyclooctenes

“…Other types of nucleophiles, including cyanide, ammonia, phthalimide and a Grignard reagent, reacted with 1 to generate the corresponding 3FGCOEs (compounds 5-7). 3-amino-COE (6) was used to synthesize 3FGCOE having amide (16) or urea (17) groups substituted at the 3-position (Scheme 1).…”

Probing the Effects of Hydrophilic Branch Size, Distribution, and Connectivity in Amphiphilic Polyethylene

“…Our recent synthesis of hydroxyl-terminated tetraethylene glycol grafted PE was the first to demonstrate such morphological control, [15] where, we concluded that the PE backbone crystallized by excluding the PEG branch based on thermal and structural investigations. For this to occur, we believe, the PEG branch must be inducing a fold in the PE backbone, thereby allowing for the clustering of the branches and allowing the backbone to form small, isolated paraffin-like crystallites ( Figure 1).…”

Criss‐cross amphiphilic polymers and analogous model systems

“…demonstrated that the folding behavior of polyethylene‐like polymers can be controlled by placing bulky substituents at periodically along the polymer backbone, which served as a folding controller . Similarly, research groups of Wagener, Winey, Mecking, and others studied folding of polyethylene‐like chains by periodic placement of hexyl, oligoethylene glycol, sulfonate or even chloro‐ substituents, along the backbone . They also demonstrated the profound effect of periodicity of the substituent on the folding behavior and the lamellar dimensions; in case of randomly distributed branch points, the polymers were found to exhibit curved and segmented morphologies .…”

“…16 Similarly, research groups of Wagener, Winey, Mecking, and others studied folding of polyethylene-like chains by periodic placement of hexyl, oligoethylene glycol, sulfonate or even chlorosubstituents, along the backbone. [17][18][19][20][21][22][23] They also demonstrated the profound effect of periodicity of the substituent on the folding behavior and the lamellar dimensions; in case of randomly distributed branch points, the polymers were found to exhibit curved and segmented morphologies. 19 More recently, our group has studied periodically grafted amphiphilic copolymers (PGACs) wherein, the immiscibility between the backbone and the pendant segments drives the polyethylene-like backbone to fold in a zig-zag conformation excluding the pendant units; these folded structures were further stabilized by the crystallization of either backbone or both backbone and pendant segments.…”