Blends of Poly(n-Vinyl-2-Pyrrolidone) and Dihydric Phenols: Thermal and Infrared Spectroscopic Studies. Part Iv

Abstract

The blending behaviour of binary systems formed by the polymer component poly(N-vinyl-2-pyrrolidone) (PVP) and the low molecular weight compounds 4,4'-biphenol (44BP) and 2,2'-biphenol (22BP) was studied. The blends were characterized in the entire composition range by Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and Scanning Electron Microscopy (SEM). Both, the glass transition temperature (Tg) and the melting point (Tm) of the pure components were affected as a consequence of the blending process. It was observed miscibility between the components in both blends and a higher interaction degree in the blend containing 44BP. FTIR analysis detected the hydrogen bonding as intermolecular interaction responsible of the observed miscibility, by means of the variation in the wave number corresponding to the stretching vibration of PVP carbonyl group. TGA and SEM analyses provided coherent and complementary results with both DSC and FTIR.

Blends of Poly(vinyl Pyridine)s and Dihydric Phenols: Thermal and Infrared Spectroscopic Studies. Part V

“…One of the analytical techniques most required for these purposes is the infrared spectroscopy [2,3,[12][13][14][15][16][17][18][19]44,[50][51][52][53], which is particularly useful to identify the kind of intermolecular interactions responsible for the miscibility between the components. A shifting in the wave number of the characteristic IR absorption bands associated to determined functional groups, can be attributed to intermolecular association [3,[14][15][16][17][50][51][52][53]. A first indication of intermolecular interaction is the position of the O-H stretch band, which can be attributed to associated O-H groups compared to unassociated O-H functions, which appear above 3600 cm -1 [54].…”

“…For these reasons, another signal was chosen: monomer units of both polymers contain pyridine groups, which show bands corresponding to the ring deformation around 993-994 cm -1 and none of the LMWCs has pyridinic rings. This vibrational mode experiences a shifting to higher wave numbers when is forming a hydrogen bonding, which is attributed to a increasing of the associated ring stiffness [50][51][52][53]55]. Figure 3 shows the wave number corresponding to the deformation absorption of pyridine groups in P4VPy and P2VPy in relation to the composition for blends A, B, C and D.…”

“…A higher content of TDP, MDP, 22BP and 44BP implies a higher content of hydroxyl groups available for the hydrogen bonding with the polymers. All LMWCs have hydroxyl groups linked to aromatic rings, which have a significant trend to hydrogen bonding formation [50][51][52][53]56,57] due to their proton-donor nature. P4VPy and P2VPy, for their part, contribute with pyridinic rings which show a high trend to accept protons [14,51,52,55].…”

“…For blends A and B, a shifting of the glass transition temperatures to lower values is registered as the content of TDP or MDP increases. An evident plasticizing effect, described in several polymer blends previously studied [32,[50][51][52][53], is observed, that is, the reduction of the Tg corresponding to the polymer component: the material becomes more flexible, improving the malleability for further use [6]. The LMWC acting as plasticizing increases the free volume between the polymer chains and so less energy is required to produce motion on chain segments.…”

“…The corresponding author and co-workers have reported a series of works dealing with functional vinyl polymers [50][51][52][53] such as poly(4-vinyl pyridine) (P4VPy) and poly(2-vinyl pyridine) (P2VPy) as polymer components and dihydric phenols as low molecular weight components. The monomer units 4vinyl pyridine and 2-vinyl pyridine are proton acceptor groups that can interact with proton donor groups such as phenolic units.…”