The linear rheological responses of wedge‐type polymers

Abstract

The linear rheological responses of a series of specially designed wedge-type polymers synthesized by the polymerization of large molecular weight monomers have been measured. These wedge polymers contained large side groups which contained three flexible branch chains per polymer chain unit. The master curves for these polymers were obtained by time temperature superposition of dynamic data at different temperatures from the terminal flow regime to well below the glass transition temperature, T g . While these polymers maintained a behavior similar to that of linear polymers, the influence of the large side group structure lead to low entanglement densities and extremely low rubbery plateau modulus values, being near to 13 kPa. The viscosity molecular weight dependence was also somewhat higher than that normally observed for linear polymers, tending toward a power law near to 4.2 rather than the typical 3.4 found in entangled linear chains. The glassy modulus of these branched polymers is also found to be extremely low, being less than 100 MPa at T g 260 C. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B:Polym. Phys. 2015, 00, 000-000KEYWORDS: branched; glassy polymers; macromonomers; rheology; viscoelastic properties; viscosity INTRODUCTION Polymer architecture has long been known to greatly affect the rheological properties of polymeric materials and, for simple linear chains, the reptation model has been highly successful in predicting the rheological behaviors.

Comb and Bottlebrush Polymers with Superior Rheological and Mechanical Properties

“…Several studies investigated the zero shear viscosity η 0 as a function of total molecular weight for different series of loose and dense bottlebrushes with either short chain branches (SCB) [13,18,19,24,[29][30][31]57] or long chain branches (LCB). [11,30] Within these bottlebrush series, two characteristics out of n sc , n g , and n bb are fixed and one of them is varied in the series.…”

“…[58] It can be seen in Figure 5b that the Rouse and reptation relaxation mechanisms have a sharp transition at M w /M e = 1. Grubbs and co-workers [13] showed that the scaling exponent of the zero shear viscosity-molecular weight dependence of a series of entangled wedge polymers (very dense bottlebrushes with three branches per repeating unit of backbone, i.e., n g ≈ 0.3) with SCB structure might be even above the 3 power law with an exponent of around 4.2. The main difference between the linear and SCBbottlebrushes is related to the friction coefficient, where in the linear polymers is due to the monomers on the backbone but in SCB-bottlebrushes is caused by monomers on the surface of the bottlebrush cylinders.…”

“…This random distribution of branch points has no distinct effect on the rheological properties of dense comb topologies; however, it will broaden the backbone relaxation time of loose comb topologies even though the molecular weight distribution is narrow enough. [13] These bottlebrushes are similar to that of the dendronized polymer with only one layer of grafting. Synthesis of welldefined densely grafted bottlebrushes using ROMP and grafting-through method guarantees the presence of one side chain per repeating unit on the backbone.…”

“…[13] These bottlebrushes are similar to that of the dendronized polymer with only one layer of grafting. Bottlebrushes with more than one branch per backbone repeating unit can also be synthesized using ROMP and macromonomers with more bulky groups referred as wedge polymers.…”

Arm‐first synthesis of star polymers with polywedge arms using ring‐opening metathesis polymerization and bifunctional crosslinkers

“…ROMP can produce polymers with large MWs and extremely narrow molecular weight distributions ( Đ ) and is used to synthesize polymers with unique characteristics. ROMP is compatible with sophisticated monomers such as macromonomers which form bottle‐brush polymers and dendritic wedge‐like monomers which form polywedges . These polymers are designed to have very high critical molecular weights and avoid chain entanglement.…”