Determination of refractive index increment of synthetic polybutadienes and microstructural control of grafting density and liquid crystalline properties

Abstract

Polybutadienes (PBs) with microstructural control of 8% to 94% moles of 1,2-olefins synthesized via living anionic polymerization (LAP) were used as precursors for the synthesis of PB-based liquid crystalline polymers (LCPs) with well-controlled grafting densities.

Well-Tailored Dynamic Liquid Crystal Networks with Anionically Polymerized Styrene-Butadiene Rubbers toward Modulating Shape Memory and Self-Healing Capacity

“…The synthesis of r -SBR- g -M was tracked by 1 H NMR in Figure b and Figure S4a, which was confirmed by the appearance of the typical peaks at δ (ppm) = 0.16–0 (−Si–(C H 3 ) 2 −) and δ = 4.40 (−O–C H 2 –CH 3 ) of M and the occurrence of the peaks at δ = 5.75–5.10 of 1,4-olefins. An approximate 50 mol % grafting density (addition efficiency, E A refers to the percentage of reactive double bonds in the total double bonds of Bd units) of r -SBR- g -M can be calculated according to Figure S5, which is in agreement with our previous work …”

“…An SiH-terminated monomer ( M ) was synthesized as in previous studies , and treated with r -SBRs bearing different MWs to obtain r -SBR- g -M bearing a 50 mol % grafting density of M during hydrosilylation as shown in the Supporting Information. GPC curves of r -SBR- g -M in Figure c show monomodal and narrow distributions (PDI = 1.03–1.08), as summarized in Table S1.…”

“…Styrene-butadiene rubber (SBR) as a general-purpose synthetic rubber has been widely applied in scientific research and industrial fields owing to its high elasticity, good wear resistance, heat resistance, and aging resistance. − Molecular compositions of rigid styrene (St) and flexible butadiene (Bd) segments of SBRs are known to be well controlled by living anionic polymerization (LAP) to achieve the desired polymer properties. − Moreover, polymerized Bd units can alter microstructures, i.e., various fractions of cis and trans units, 1,2-olefins and 1,4-olefins, which offer structural diversity as a powerful research tool for the design of novel functional materials. − Since the properties of polymeric materials are largely a result of the molecular compositions of polymer chains, the well-tailored construction of polymer chain architecture through quantitative synthesis proves to be a powerful strategy for manipulating polymer properties. , …”

“…In the present work, anionically polymerized random styrene-butadiene rubbers ( r -SBRs) with well-designed molecular weights ( M n = 21.5 kg/mol, polydispersity index (PDI) = 1.06; M n = 35.4 kg/mol, PDI = 1.06; M n = 47.2 kg/mol, PDI = 1.03) are prepared, and their overall 75 wt % Bd contents are designed to improve molecular mobility, as LAP is desirable for tailoring polymeric templates with well-controlled molecular compositions to manipulate the properties. − The microstructures of Bd units are also designed according to our previous work, , which used 51.5–64.0 mol % 1,2-olefins to achieve almost 50 mol % attachments along Bd units during the post-modification of r -SBRs. As shown in Figure , SiH-terminated mesogenic moieties ( M ) were grafted onto r -SBR for the synthesis of r -SBR- g -M bearing a well-designed 50 mol % grafting density through hydrosilylation.…”

Molecular Dispersion of Starch as a Crucial Parameter during Size-Exclusion Chromatography

“…RI signal (RI area ) is described by the following equation: RI area = k′ × (dn/dc) × m inj [ 48 ], where: k′ is the instrument constant of the RI detector ( k / n 0 ; the refractometer response constant, k , the refractive index of the solvent, n 0 ), m inj is the total injected mass calculated from the injected concentration and the injection volume (m inj = c inj × V inj ). The M w was calculated from the Rayleigh equation limited for low scattering angles ( Kc /∆ R θ = (1/M w + 2 A 2 c)1/ P θ ,) where: c is the concentration of the polymer; ∆ R θ the Rayleigh ratio (defined as the amount of light scattered by the analyte solution in excess of that scattered by the solvent at a given angle θ ), A 2 the second viral coefficient (in the limit of zero angle and near-infinite dilution this coefficient can be neglected); K the optical constant K = (4π 2 n 0 2 /N A λ 4 )(dn/dc) 2 ; n 0 the solvent refractive index; λ the laser wavelength; and N A is Avogadro’s number), P θ is a form factor related to the size of the molecule and the angle at which the scattering is determined, at θ = 0°, P θ = 1 [ 36 , 49 , 50 ].…”