MISCIBILITY BEHAVIOUR OF BLENDS OF FLOURINE-CONTAINING POLY(ALKYL METHACRYLATE)S WITH CONVENTIONAL POLYMETHACRYLATES, POLYACRYLATES, POLYESTERS, TERTIARY AMIDE POLYMERS AND STYRENIC COPOLYMERS

Abstract

The purpose of this work is to study the miscibility behaviour of blends of various fluorine-containing polymethacrylates with poly(alkyl methacrylate)s, poly(alkyl acrylate)s, poly(vinyl acetate), aliphatic polyesters, styrenic copolymers with tertiary amide polymers, in order to understand the relationship between the miscibility behaviour and the molecular structure of polymers. The miscibility behaviour is determined by optical appearance as well as by differential scanning calorimetry (DSC). The intermolecular interaction was studied by Fourier-transformed infrared spectroscopy (FTI.r.). The surface properties of some homopolymers and polymer blends were also investigated by contact angle and X-ray photoelectron spectroscopy (XPS) analysis. The fluorine-containing polymethacrylates studied in this work are poly(2- fluoroethyl methacrylate) (P2FEMA), poly(3-fluoropropyl methacrylate) (P3FPMA), poly(4-fluorobutyl methacrylate) (P4FBMA), poly(1 ,3-difluoroisopropyl methacrylate) (PDFPMA) and poly( 1, 1, 1,3,3,J-hcxarluoroisopropyl methacrylate) (PHFPMA). For the complementary study of the miscibility behaviour of chlorine-containing polymethacrylates, poly(1-chloroethyl methacrylate) (P1CEMA) is also included. The miscibility behaviour of fluorine-containing polymethacrylates and P1CEMA was compared with other halogen-containing polymethacrylates. The miscibility and intermolecular interaction strength between a halogen-containing polymethacrylate and various poly(alkyl methacrylate)s decrease with increasing size of the alkyl pendent group of the poly(alkyl methacrylate). Specific interactions such as hydrogen bonding between two polymers are suggested to be the main driving force for the miscibility. The presence of halogen atom increases the acidity of the a-hydrogen of a halogen-containing polymethacrylate, resulting in the strong intermolecular interaction. The type, number and position of halogen incoperation will affect the acidity of the a-hydrogen. The miscibility of various halogen-containing polymethacrylates with a poly(alkyl methacrylate) correlates well with the acidity of their ?-hydrogen except for P2FEMA and PHFPMA which have the tendency to undergo self-association. Intermolecular dispersive interaction, which is determined by the solubility parameter difference (??nh) between two components of the blend, should also be taken into consideration. The good miscibility of chlorine-containing polymethacrylates with PTHFMA and poly(alkyl methacrylate)s having small pendent group is attributed to the closely matched solubility parameters (?nh) of two components of the blend, as well as the strong intermolecular interaction. The miscibility of halogen-containing polymethacrylates with different type of halogen was also well explained from the viewpoint of dispersive and specific interaction forces. Halogen-containing polymethacrylates are less readily miscible with poly(alkyl acrylate)s than with poly(alkyl methacrylate)s. However, the miscibility range still correlates well with intermolecular interaction strength. The poor miscibility of fluorine-containing polymers is attributed to their preference to undergo self-association rather than intermolecular association. "Miscibility windows" were found for the blends of some halogen-containing polymethacrylates with poly(alkyl acrylate)s. PTCEMA, PDCEMA, PCMMA and P1CEMA are miscible with poly(alkyl acrylate)s having intermediate CH2/COO ratios, such as PEAA and PPAA, but immiscible with PMAA. Similar "miscibility windows" were also found for P3FPMA, P4FBMA and PDFPMA with various polyesters having CH2/COO ratios of 2 to 7 in their repeat unit, and P1CEMA also showed maximum intermolecular interaction with aliphatic polyesters having intermediate CH2/COO ratios. The miscibility map of the volume fraction of -COO-groups (?COO) of the poly(alkyl acrylate), poly(alkyl methacrylate)s or aliphatic polyesters against the sum of the volume fractions of -COO- groups and halogen-containing -CHX- (?COO+CHX) of the halogen-containing polymethacrylates shows well defined miscibility range, indicating that both intermolecular and intramolecular interactions are important in achieving the miscibility. The miscibility of various halogen-containing polymethacrylates with PV Ac was found to be affected by the casting solvent. MEK was a better solvent for forming the miscible blends than THF. FTI.r. analysis showed the existence of intermolecular hydrogen bonding involving the carbonyl group of PVAC, and the strength in the blend cast from MEK is stronger than in the blend cast from THF. PICEMA, P2FEMA, P3FPMA and P4FBMA are all miscible with SAN and pMSAN over certain composition ranges, whereas PDFPMA and PHFPMA are immiscible with these copolymers. The "repulsive interaction" analysis showed that the interaction of methacrylate segment with acrylonitrile segment is strongly repulsive while that with styrene or p-methylstyrene segment is only weakly repulsive. The repulsive interaction is also affected by the size of pendent group of the methacrylate, the type of halogen incorporated, as well as the site of halogen incorporation. The repulsive interaction between the different segments comprising the copolymer is stronger than the repulsion between the homopolymer and copolymer segments, resulting in the miscibility window. P1CEMA, P2FEMA, P3FPMA and POFPMA are all miscible with PVP, PMVAc, POMA and PEOx from OMF. Intermolecular complexes were obtained upon mixing THF solutions of P3FPMA and PMVAc. FTi.r. measurement showed that hydrogen bonding interactions exist in each of the blends of P3FPMA with PMVAc, POMA and PEOx. The strength of hydrogen bonding increases with increasing of P3FPMA content in the blend. Moreover, an increase of temperature leads to the dissociation of hydrogen bonding. The relative strength of hydrogen bonding decreases in the order PMVAc >POMA> PEOx. Whereas, a self-association, or intramolecular hydrogen bonding, was found in PHFPMA. No apparent hydrogen bonding was observed between PHFPMA or P2FEMA and three tertiary amide polymers. Surface tension measurements showed that the surface tensions of various fluorine-containing polymethacrylates decrease with increasing length of the side chain and the numbers of fluorine atom. Surface tensions of PHFPMA/PMMA and PHFPMA/PEMA blends are all close to that of PHFPMA, showing the surface enrichment of PHFPMA. However, no conclusive results were obtained for P2FEMA/PMMA and P2FEMA/PEMA blends. XPS measurements showed that the surface of PHFPMA/PMMA and PHFPMA/PEMA blends are mainly covered by PHFPMA, further confirming the contact angle measurement results.