A Facile Route to Synthesize Well‐Defined Polybutadiene DendriMacs

Abstract

A facile route to synthesize well‐defined polybutadiene (PBd) DendriMacs is described. In a highly modified approach to that recently published for the synthesis of polystyrene DendriMacs, a G1 polybutadiene (PBd) DendriMac has been synthesized in three simple and high yielding steps. The first step involves the synthesis of a three‐arm PBd mikto arm star in which one arm has a terminal hydroxy group introduced by the use of a protected functionalized initiator. Following fractionation of the star, the hydroxy group is deprotected and converted into an alkyl bromide moiety before coupling the star to a trifunctional core (1,1,1‐tris(4‐hydroxylphenyl)ethane) by a Williamson coupling reaction catalyzed by cesium carbonate to yield a G1 PBd DendriMac.

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

“…A mole ratio of 2.5 : 1 (long arm : short arm) was used in all cases. This mole ratio has been shown to be optimal for analogous reactions described elsewhere [33,38]. As well as describing the two synthetic strategies we will compare the efficiency of the two approaches.…”

“…Star polymers with varying numbers of arms have been widely produced and studied [1][2][3][4][5][6][7][8] and branched polymers of increasing complexity and diverse structures have evolved. These include H-shaped polymers [9][10][11][12][13][14][15], comb-shaped polymers [16][17][18][19][20][21][22][23][24][25][26][27][28] and more recently dendritically branched polymers [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. Fundamental to all these studies is the ability of the synthetic polymer chemist to control structural homogeneity and produce branched ...…”

“…One might describe these asymmetric star polymers as 'mikto' star polymers, in so much that the nature of the arms varies in respect of molecular weight. Whilst it would have been possible to prepare such a series of stars by the more traditional approach for the synthesis of mikto stars first reported by Hadjichristidis [53], namely by the arm-first methodology and a chlorosilane coupling agent such a methyltrichlorosilane -a method exploited previously by us for the synthesis of isotopic mikto arms stars [2] and DendriMacs [38] -it would not be possible to produce a series of stars in which the effective chain length of the linear backbone polymer was identical in every case. Even the most careful use of anionic polymerisation results in some batch to batch variation in molecular weight.…”

“…Even the most careful use of anionic polymerisation results in some batch to batch variation in molecular weight. The 'macromonomer' approach, first reported by our group for the synthesis of complex dendritically branched polymers such as DendriMacs [33,38], HyperMacs [54][55][56] and more recently HyperBlocks [57], has become widely adopted as a useful route to make a variety of complex dendritic branched architectures with polymer segments between branch points [58][59][60][61][62][63][64][65][66][67]. In essence the 'macromonomer' approach involves the synthesis of the linear segments of a branched polymer by a living/controlled polymerisation mechanism such that the linear segments contain chain-end functionalities which allow the subsequent construction of branched polymers via coupling reactions between macromonomers.…”

In Silico Molecular Design, Synthesis, Characterization, and Rheology of Dendritically Branched Polymers: Closing the Design Loop

“…Quirk et al 36 have previously reported arm cleavage when hydrolysis was carried out for a prolonged reaction time in an identical deprotection reaction on similar star branched polymers: an observation that we also initially made during the synthesis of the DendriMac. 17 To minimize arm cleavage, the deprotection reaction was carried out under high vacuum for only 30 min in presence of BHT (0.1% w/w) at 70°C, however, it is possible that arm cleavage was not completely eliminated. Although the intermediate star was fractionated to give a monomodal, narrow polydispersity peak, it is likely that SEC would be unable to resolve the star from traces of the defect with one of the shorter arms missing, and such a defect would be able to take part in the subsequent coupling reactions to form the DendriMac.…”