Rheological characterization and modeling of end-functionalized polybutadienes

• Published in: Rheologica acta Vol. 42; no. 1-2; pp. 171 - 183
• Main Authors: GARCIA-LEINER, Manuel, MANERO, Octavio, HERRERA, Rafael
• Format: Journal Article
• Language: English
• Published: Berlin Springer 2003; Springer Nature B.V
• Subjects: Applied sciences; Butyllithium; Chain entanglement; Constitutive equations; Constitutive relationships; Exact sciences and technology; Functional groups; Initiators; Maxwell's equations; Modelling; Molecular weight; Molecular weight distribution; Organic polymers; Physicochemistry of polymers; Polybutadiene; Polydispersity; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Propylene oxide; Reptation; Rheological properties; Rheology; Rubber; Solution polymerization; Termination (polymerization); Viscosity; Viscosity; Rheological model; End group; Molecular structure; Priming activity; Organic siloxane; Organic silane; Experimental study; Solution polymerization; Lithium Organic compounds; Butadiene polymer; Anionic catalyst; Anionic polymerization; Property structure relationship; Comparative study; Rheological properties; Functional group
• ISSN: 0035-4511; 1435-1528
• DOI: 10.1007/s00397-002-0269-4

The rheological characterization and modeling of a series of polybutadienes obtained by anionic solution polymerization is presented in this work. The polybutadienes are synthesized using two different initiators: R,R′,R′′-silyloxyalkyllithium (F1) and R,R′,R′′-silylalkyllithium (F3). In addition, a polybutadiene obtained with a conventional alkyllithium initiator (n-butyllithium) is used as a reference.The rheological characterization is carried out under small amplitude oscillatory shear in the stress-controlled mode. Microstructure, molecular weight, and molecular weight distribution are determined by FTIR and GPC. The vinyl content of the polybutadienes synthesized using the functionalized initiators is similar to that obtained with n-butyllithium (8–11%). Materials obtained with F1 show a relatively low polydispersity within a narrow molecular weight range (250,000–300,000 g/mol), while samples obtained with F3 cover a wider range of molecular weights (65,000–670,000 g/mol) and display higher values of polydispersity. In all cases, a parallel reaction using propylene oxide in the termination step is done to place a functional group at the chain ends. The effect of this group on the rheological behavior appears to be negligible.Three rheological models are used and their predictions of the experimental data are compared. The models include the Doi and Edwards reptation model, expressions using a discrete spectrum of relaxation times based in the rubber-like liquid constitutive equation and the fractional Maxwell equation in which a given analytical relaxation-spectrum is used. Relevant relations are obtained between the models' parameters and the molecular properties of these systems, which in turn are related to the presence of functional groups at the polymer chain ends.