Polybutadiene macroinitiator

Initial reports on chemoenzymatic block copolymer synthesis focus on the enzymatic macroinitiation from chemically obtained hydroxy-functional polymers (route A in Fig. 4). The first report on enzymatic macroinitiation was published by Kumar et ah, who used anionically synthesized hydroxy-functional polybutadiene of various molecular weights ranging from 2600 to 19,000Da (Fig. 5) [16]. In a systematic study, the authors investigated the efficiency of the macroinitiation of CL and PDF by Novozym 435 as a function of the polybutadiene macroinitiator. The reaction profile showed that polybutadiene consumption steadily increased with the reaction... 

Besides the use of micromolecular multiinitiators, block copolymers can be obtained from macromolecular initiators. In a first step, a polymeric initiator is generally synthesized by reacting a mono- or difunctional polymer with a functional initiator. Various macromolecular initiators were prepared in this way including quite different sequences polystyrene [13, 18, 19, 25, 26], poly(dimethylsiloxane) [27], polymethylmethacrylate) [13,15,28], polyvinylacetate [28], polyvinylchloride [29, 30], polyesters [30], polycarbonate [31,32], polybutadiene [13, 25, 33], polyamide [34], polyethylene glycol) [35] or polyaromatic [36], An excellent review of the synthesis and uses of such macroinitiators was written by Nuyken and Voit [37]. Thus, only few typical examples are going to be mentioned below. 

Flydroxyl-capped poly (ethylene-co-butylene), a so-called Kraton, was converted into a macroinitiator via esterification with 2-bromopropionyl chloride, and then employed for the block copolymerizations of styrene and />acetoxystyrene (B-116 and B-117).403 A similar method is utilized for B-l 18 to B-121 where the esterification is with 2-bromoisobutyroyl bromide.341 A commercially available polybutadiene is also employed for B-122 via a similar transformation into the chloroacetyl group.404... 

Figure 12.1 Synthesis of poly(butadiene-b-caprolactone) from hydroxyl functional polybutadiene. The plot shows the consumption of the macroinitiator ( ) and...

Trimethylazetidine was polymerized by this macroinitiator, and ABA block copolymers were obtained. Reaction with a polyfunctional nucleophile such as diethylenetriamine leads to high molecular weight polymers and eventually cross-linking. The coupling reaction with amino-terminated polybutadiene polymers led to polyblock copolymers (47). 

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. ... 

A tadpole polybutadiene with two linear PS chains has been prepared by Quirck and Ma living anionic poly(styryl) lithium chains were first coupled by reacting the living ends with the double diphenylethylene. Then the resulting polymer bearing two reactive catbanionic centers located in the middle of the chain was used as a bifimcdonal macroinitiator to initiate the anionic polymerization of butadiene. The two... 

Similarly ABA triblock copolymers, PSt-i-PEO-i-PSt have been prepared by the ATRP of St with the difunctional macroinitiator, a, co-bis-(2-chloropro-pionyl) PEO in conjunction with CuCl/bpy. By reacting ot, co-hydroxyl-termin-ated poly(propylene oxidejs or polyesters or polybutadienes with chloroacetyl chloride in toluene, a, co-dichloroacetyl polymers were obtained and used as macroinitiator in the ATRP of St. The series of triblock copolymers, LMB-4, LMB-5, LMB-6 were thus successfully prepared [77-80]. 

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