COMPLEXATION AND MISCIBILITY BEHAVIOUR OF TERTIARY AMIDE POLYMERS

Abstract

The miscibility and interpolymer complexation behaviour of a series of polymer blends arising from hydrogen bonding interactions was studied by differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTi.r.). It has been reported that polymeric proton donors such as carboxyl- and phenolic group-containing polymers can readily form interpolymer complexes with many non-ionic polymeric proton acceptors. The purpose of this work was to further investigate the interpolymer complex formation and miscibility of aliphatic hydroxyl-containing polymers, which are weaker proton donors than carboxyl- and phenolic group-containing polymers, with tertiary amide polymers. Such aliphatic hydroxyl-containing polymers include poly(styrene-co-allyl alcohol) (SAA), poly(hydroxyether of bisphenol-A) (phenoxy) and poly(2-hydroxypropyl methacrylate) (PHPMA) and tertiary amide polymers include poly(N-methyl-N-vinylacetamide) (PMVAc), poly(N,N-dimethylacrylamide) (PDMA), poly(2-ethyl-2- oxazoline) (PEOx) and poly(N-vinyl-2-pyrrolidone) (PVP). In addition, the miscibility and complexation behaviour of several other polymeric proton donor/acceptor pairs was also studied. The miscibility and complexation behaviour of SAA and four tertiary amide polymers, PVP, PMVAc, PDMA and PEOx, was studied using different solvents. When using MEK as the solvent, SAA forms complexes with PVP and PMVAc at the whole feed composition range and with PDMA at feed compositions less than 50 wt% of POMA but does not form complexes with l'EOx over the entire feed compositions. When using MEK as the solvent, SAA forms complexes with PYP at the whole feed composition range anti with PMY Ac anti POMA at certain feed composition range bul does not form complexes with PEOx at the whole feed composition range. On the other hand, SAA does not form complexes with the four tertiary amide polymers in DMF solutions. The above results show that both the nature of solvents and the structure of tertiary amide polymers strongly affect the complex formation of these polymer blends. The relative abilities of the four tertiary amide polymers to form intermolecular complexes with SAA are in the order of PVP > PMVAc > POMA > PEOx. FTi.r. studies show that the hydrogen bonding interactions between the SAA hydroxyl groups and the carbonyl groups in polymeric tertiary amides initiate the intermolecular complexation and their relative strengths are in agreement with their relative abilities in forming interpolymer complexes. Besides SAA, other aliphatic hydroxyl-containing polymers such as phenoxy and PHPMA are also found capable of forming complexes with tertiary amide polymers. Phenoxy forms interpolymer complexes with PYP, PMVAc and PDMA from THF solutions at the entire feed composition range, but not with PEOx. PHPMA forms interpolymer complexes with PMVAc, PDMA and PEOx at the entire feed composition range in THF and MEK solutions, but not in DMF solutions. The results demonstrate that the relative abilities of the four tertiary amide polymers to form interpolymer complexes with phenoxy and PHPMA are in the order of PVP > PMVAc > PDMA > PEOx, same as the SAA/tertiary amide polymer systems, and the relative abilities of aliphatic hydroxyl containing polymers with these tertiary amide polymers are in the order of PHPMA > phenoxy > SAA. Poly(2-methyl-2-oxazoline) (PMOx), an analogue of PEOx, forms miscible blends SAA, phenoxy and PI IPMA in OMF solutions. Comparing the hydroxyl and carbonyl regions of the infraretl spectra of the blends of PMOx and PEOx with aliphatic hydroxyl-containing polymers, the former shows stronger hydrogen bonding interactions witl1 aliphatic hydroxyl-containing polymers than the latter. On the other hand, PMOx forms interpolymer complexes with PVPh in methanol solutions and forms miscible blends with PVPh in DMF solutions, Both the miscibility and complexation abilities, and the infrnred studies indicate stronger intermolecular interactions in the PMOx/PVPh system than in the PEOx/PVPh system, AM1* calculation results suggest that steric factor plays an important role in the complexation anti miscibility behaviour. The smaller methyl group in PMOx allows a better contact between the carbonyl group and the hydroxyl group, The miscibility and complexation behaviour of other polymeric proton donor/acceptor pairs, poly(p-vinylphenol) (PYPh)/pyridine containing polymers, was studied. PVPh forms complexes with poly(2-vinylpyridine) (P2VPy), poly(4- vinylpyridine) (P4VPy) and poly(2-vinylpyridine-co-styrene) (P2VPyS) over the entire feed composition range in ethanol solutions, but not in DMF solutions. The complexation abilities of the three pyridine-containing polymers with PVPh from ethanol solutions were found to be in the order P4YPy > P2YPy > P2VPyS. FTi.r. studies show that the relative strengths of the hydrogen bonding interactions between PVPh hydroxyl groups and pyridine nitrogen atoms of the three pyridine-containing polymers are in agreement with their complexation abilities. The introduction of sulfonic acid groups into polystyrene generates favourable interpolymer interactions with tertiary amide polymers and results in the formation of miscible blends or interpolymer complexes, The miscibility and complexation behaviour of three sulfonated polystyrene (SPS), with sulfonation degrees of 27, 17 and 6.5 % and denoted as SPS(27), SPS(17) and SPS(6), with tertiary amide polymers was studied. When using THF as the solvent, PVP, PMVAc and PDMA form complexes with all the three SPS samples over the entire feed composition range, PEOx forms complexes with SPS(27) and SPS(17) and forms miscible blends * AM 1 - Austin Model 1 with SPS(6) at the entire feed composition range. When using DMF as the solvent, miscible blends form for PVP/SPS(6, 17, or 27), PMVAc/SPS(27) and PMVAc/SPS(17) at the whole composition range and immiscible blends form for PMVAc/SPS(6), PDMA/SPS(6, 17, or 27) and PEOx/SPS(6, 17, or 27) al certain compositions. Based on the above results, the relative complexation abilities of tertiary amide polymers with SPS are in the order of PVP > PMVAc > PDMA > PEOx, same as that observed in aliphatic hydroxyl-containing polymer/tertiary amide polymer systems. The ability of SPS to form miscible blends or interpolymer complexes with tertiary amide polymers increases with increasing degree of sulfonation. A sulfonation degree of 17 % is sufficient lo result in the formation of interpolymer complexes with all the four tertiary amide polymers in THF solution. X-ray pho10elecu·on microscopy (XPS) was used to characterize the interpolymer complexes between SPS and poly(styrene-co-4-vinylpyridine) (PSVP) with similar content of sulfonic acid and pyridine functional groups. The results show that over 50% of protons were transferred from the sulfonic acid groups to the nitrogen atom of pyridine, confirming that the driving force for complex formation was ionic interactions.