Polystyrene with dendritic branching by convergent living anionic polymerization. II. Approach using vinylbenzyl chloride

Abstract

Vinylbenzyl chloride (VBC) has been used as a coupling agent in Convergent Living Anionic Polymerization to produce polymers with dendritic branching. The slow addition of a stoichiometric amount of VBC to living polystyrene chains allows the coupling to proceed through macromonomer formation followed by vinyl addition. Changing the reaction conditions produced two types of structures. Star‐shaped polymers with a hyperbranched core were made by the continuous slow addition of VBC alone, and chain‐extended hyperbranched structures with varied molecular weight between branch points were produced by the slow addition of VBC mixed with different amounts of styrene monomer. The extent of growth of the two different types of structures ranged from 2.4 to 2.6 generations for the case of VBC added alone, corresponding to an average of 5.3 to 6.1 arms attached to the hyperbranched core, and from 3.2 to 4.2 generations for polymers produced from the addition of VBC mixed with styrene. Relatively low polydispersities were obtained for all samples. The highly branched nature of the polymers was reflected in the low intrinsic viscosity relative to linear polystyrene and in the dependence of glass‐transition temperature on the molecular weight relative to the number of end groups. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4289–4298, 2000

HyperMacs – long chain hyperbranched polymers: A dramatically improved synthesis and qualitative rheological analysis

“…al. [11,18] who reported a similar behaviour for hyperbranched polystyrenes with M w in excess of 10 6 gmol -1 . Clearly the apparent absence of entanglements is the result of the highly branched architecture.…”

“…It is this realisation that has, over a period of decades, resulted in the design and synthesis of well-defined molecular architectures such as star branched polymers [2,3], mikto star polymers [4][5][6] and H-shaped polymers [7,8] with a view to understanding and predicting the relationship between structure and properties. More recently, syntheses of dendrigraft, dendritically branched and arborescent [9][10][11][12][13][14] polymers with a higher degree and complexity of branching have been published, much of this work has recently been reviewed by Gauthier and Teertstra [15]. One of the earliest investigations into the synthesis [16] and characterisation of the rheological properties [17] of arborescent type polymers are reported by Gauthier et al who studied the viscoelastic behaviour of these materials with increasing generations (increased levels of hierarchical branching).…”

“…The results demonstrate that these branched polystyrene architectures have low zero-shear viscosities when compared to linear polystyrene of the same molecular weight. Knauss synthesised [10][11][12] and examined the melt rheology [18] of dendritically branched polystyrene and observed that these randomly branched polystyrenes with molecular weights above 1.0 x 10 6 gmol -1 exhibit high melt elasticity, but show little evidence of entanglement. However, in both these described architectures the synthetic strategies offer little or no control over the molecular weight between branch points.…”

Chain Architecture as an Orthogonal Parameter To Influence Block Copolymer Morphology. Synthesis and Characterization of Hyperbranched Block Copolymers: HyperBlocks

“…Common approaches to introduce a linear polymer segment between branching points in LCHBPs include selfcondensing vinyl polymerisation (SCVP) [40][41][42][43] and the so called "Strathclyde approach" 44 which exploits radical polymerisation, a divinyl comonomer and a chain transfer agent to prevent gelation. Knauss [45][46][47] reported the synthesis of dendritically branched polystyrene prepared by anionic polymerization in which styrene was polymerized in the presence of either vinylbenzyl chloride (VBC) or 4-(chlorodimethylsilyl)styrene (CDMSS). Each comonomer is capable of a dual role; the vinyl group enables VBC and CDMSS to take part in the polymerization and the chloromethyl/chlorosilane functionalities are susceptible to nucleophilic attack by polystyryllithium resulting in the introduction of a branching point.…”

DendriMacs. Well-Defined Dendritically Branched Polymers Synthesized by an Iterative Convergent Strategy Involving the Coupling Reaction of AB2 Macromonomers

“…The design and synthesis of new, well-defined molecular architectures such as star branched polymers 1,2 , mikto star polymers [3][4][5] and H-shaped polymers 6,7 has contributed much to understanding and prediction of the relationship between structure and properties. More recently numerous strategies have been devised to synthesize more complex branched architectures with various resulting structures and differing degrees of control, including syntheses of dendrigraft, dendritically branched and arborescent [8][9][10][11][12][13] polymers, much of this work has recently been reviewed by Gauthier and Teertstra 14 . A number of examples of well defined dendritically branched polymers, essentially analogues of classical dendrimers with an additional polymer chain between branch points have also been reported, notably by Hadjichristidis 15 , Gnanou 8,16 , Hedrick 17 and Hirao 18,19 .…”