Primary Amine Macroinitiators

Most of these hybrid copolymers involve the use of telechelic poly(ethylene oxide), PEO, carrying amine end groups. This interest can be attributed to the fact that the amino-PEOs are commercially available in a variety of molecular weights with narrow molecular-weight distributions, are water soluble and biocompatible. Furthermore, these PEO polypeptide hybrids can form amphiphilic, double-hydrophilic and rod-coil-rod block copolymers, leading to materials with very interesting properties in solution and in bulk. 

Yang et al, 2005) and poly[(DL-Val)-co-(DL-Leu)]-/7-PEO-fe-poly[(DL-Val)-co-(DL-Leu)] (Cho et al, 2003) have been prepared. Earlier studies resulted in poorly defined products, since diblocks and homopolymers were present in the final reaction products. 

The general synthetic scheme for the polyester hybrids starts with the synthesis of the diamino polyester (A) macroinitiators, followed by the ROP of the desired NCA to give the corresponding BAB hybrids (B are the polypeptide chains). 

Linear pentablock terpolymers PBLL-Z -PBLG-Z -PS-Z -PBLG-Z -PBLL (BLL r -butylox-ycarbonyl-L-lysine, PS polystyrene) were recently synthesized by Karatzas et al. (2008) using a,co-diamino-PS. This polymer was prepared by anionic polymerization of styrene with sodium/naphthalene (difunctional initiator) and termination with l-(3-bromo-propyl)-2,2,5,5-tetramethyl-aza-2,5-disilacyclopentane, and of deprotection by successive 

---

In the past two years, a number of new approaches have been reported for obtaining controlled NCA polymerizations. These approaches share a common theme in that they are all improvements on the use of classical primary amine polymerization initiators. This approach is attractive since primary amines are readily available and since the initiator does not need to be removed from the reaction after polymerization. In fact, if the polymerization proceeds without any chain breaking reactions, the amine initiator becomes the C-terminal polypeptide end-group. In this manner, there is potential to form chain-end-functionahzed polypeptides or even hybrid block copolymers if the amine is a macroinitiator. The challenge in this approach is to overcome the numerous side-reactions of these systems without the luxury of a large number of experimental parameters to adjust. 

PNIPAM-PAPAT), was realized by RAFT. In the first step, the polymerization of PNIPAM was achieved and the as synthesized polymer was used as the macroinitiator for the polymerization of APAT. However, in order to polymerize primary amine containing monomers, acidic media are needed in order to eliminate some side reactions (the primary amine moieties have to be protonated in order to suppress the side reactions). 

Gallot et al. published one of the earliest reports on the preparation of PLL-based hybrid block copolymers. The synthetic segments in these copolymers were primary amine-terminated polystyrene or polybutadiene that were used to initiate the ROP of ZLL-NCA. The authors intended to use the hybrid conjugates as a model for biological membranes. In the following years, several reports emerged on the synthesis of PLL hybrid block copolymers based on macroinitiators prepared by vinyl monomer polymer-ization. ° The pH and temperature dependence of the copolymer vesicles formed in solution was investigated. ... 

Basically, intermediate polymeric anions were reacted with l-(3-bromopropyl)-2,2,5,5-tetramethyl-aza-2,5-disilacyclopentane, followed by spontaneous deprotection during workup to prepare well-defined in-chain- or core-functionalized star-branched polymers with primary amine group(s). These functionalized polymers could be used as macroinitiators for the living polymerization of NCAs. The success of those star-polymer syntheses may be derived from the 100% introduction of primary amino groups at the precise position and extremely clean media for NCA polymerization in completely sealed reactors based on the high-vacuum technique. 

In other words, polymerization occurred from all four N-H-bonds of the PEO macroinitiator (Scheme 34). A model primary amine initiator, namely 1-aminomethylpyrene, was... 

The synthesis of temperature-responsive poly[(TMC)-b-(i-glutamic acid)] copolymer was investigated by Sanson and co-workers. PTMC-PGA diblock copolymer was synthesized by ROP of y-benzyl-L-glutamate N-carboxyanhydride initiated by a primary amine end-functionalized PTMC macroinitiator. 

---