Biemond, G.J.E.

Gaymans, R.J.

Krijgsman, J.

Stephen, R.

English

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High Tg segmented copolymers with monodisperse crystallisable segments

University of Twente Research Information

Proceedings Published 2007 by the American Chemical SocietyHIGH Tg SEGMENTED COPOLYMERS WITH MONODISPERSE CRYSTALLISABLE SEGMENTS  J. Krijgsman, G.J.E. Biemond, R. Stephen, R.J. Gaymans  Twente University P.O. Box 217, 7500 AE Enschede, The Netherlands  Introduction  Segmented copolymers consisting of amorphous poly(2,6-dimethyl-1,4-phenylene ether) (PPE) (also called PPO) segments, crystallisable tetra-amide units (up to 20 wt%) and spacer groups (-spacer-T-PPE-T-spacer-T6T6T-) have been studied .1-3 The monodisperse tetra-amide units T6T6T are two and a half repeat unit of PA-6,T. The copolymers are semi-crystalline materials with a high Tg (170-180 °C) combined with a not too high melting temperature (260-275 °C) and have thus an extremely high Tg/Tm ratio (>0.8). This is very particular because crystallization is normally absent in (co)polymers with a high Tg/Tm ratio.4,5 The uniform length T6T6T segments form ribbon-like crystalline structures with a very high aspect ratio dispersed in the amorphous matrix.6-9 The copolymers are good melt processable and have good solvent resistance and low water absorption. Increasing the spacer group length decreases the Tg of the system a bit but increases the storage modulus between Tg and Tm.10 Interesting is to study if high molecular weight PPE-T6T6T copolymers can be made without spacer units and what the properties of these copolymers are. Without spacer units the copolymer synthesis is in less steps and thus simpler. The starting telechelic PPE has two hydroxylic groups (PPE-2OH) (Fig.1) and a molecular weight of 3500 g/mol.11  Figure 1. Structures of PPE-2OH and T6T6T-diphenyl  As the reactivity of the phenolic hydroxylic group in PPE is low the used ester group should be very reactive like a phenolic ester.  A polymerisation is possible of PPE-2OH and the diphenyl ester of T6T6T (T6T6T-diphenyl) are used (Fig. 1).12 As T6T6T-diphenyl is a high melting compound (312 °C 12) and the polymerisation temperature is 280 °C, a solvent is needed in the initial stage of the reaction. The aim of the present work is to study the synthesis and properties of (-PPE-T6T6T-) segmented copolymers based on difunctional PPE segments (PPE-2OH) and T6T6T-diphenyl. The T6T6T content in the copolymers was varied by replacing some of the T6T6T-diphenyl with diphenyl terephthalate (DPT).  Experimental  Materials. N-methyl-2-pyrrolidone (NMP) was purchased from Merck. Tetra-isopropyl orthotitanate (Ti(i-OC3H7)4), obtained from Merck, was diluted in anhydrous m-xylene (0.05M), obtained from Fluka. A poly(2,6-dimethyl-1,4-phenylene ether), PPO-803® (11,000 g/mol), was obtained from GE Plastics (The Netherlands). Telechelic PPE-2OH with a number average molecular weight of 3500 g/mol and 450 µmol OH/gram was made according to.11 All chemicals were used as received. Uniform T6T6T-diphenyl (>95% uniform), 6T6-diamine and diphenyl terephthalate (DPT) were synthesised as described before.12  Synthesis of -PPE-T6T6T- copolymers The preparation of an alternating segmented block copolymer of PPE-2OH and T6T6T-diphenyl is given as an example. For copolymers with lower T6T6T contents part of the T6T6T-diphenyl was replaced by DPT to retain stoichiometry and high molecular weight.  The reaction was carried out in a 50 ml glass reactor with a nitrogen inlet and mechanical stirrer. The vessel was loaded with PPE-2OH (10.0 g, 4.50 mmol OH), T6T6T-diphenyl (1.82 g, 2.25 mmol), 20 ml NMP and catalyst solution (0.6 ml of 0.05M Ti(i-OC3H7)4 in m-xylene). This mixture was first heated in an oil bath to 180°C under nitrogen flow. Then the temperature was raised in steps: 30 min 180 °C, 30 min 220 °C, 60 min 250 °C and 120 min 280 °C. Subsequently the pressure was then carefully reduced (P<20 mbar) to distil off the remaining NMP in 60 minutes and then further reduced (P<1 mbar) for 60 minutes. Finally, the vessel was allowed to slowly cool to room temperature whilst maintaining the low pressure. Then the polymer was removed from the reactor and powdered.  Viscometry. The inherent viscosity of the polymers was determined with a capillary Ubbelohde type 1B at 25°C, using a polymer solution with a concentration of 0.1 g/dl in phenol/1,1,2,2-tetrachloroethane (50/50, mol/mol).  Dynamic Mechanical Analysis. Samples for the Dynamic Mechanical Analysis (DMA) test (70x9x2 mm3) were prepared on an Arburg-H manual injection molding machine. Before use, the samples were dried in a vacuum oven at 80 °C overnight. The DMA behavior in torsion was studied at a frequency of 1 Hz, a strain of 0.1% and a heating rate of 1 °C/min using a Myrenne ATM3 torsion pendulum. The storage modulus G’ and loss modulus G” were measured as a function of temperature. The glass transition temperature (Tg) was expressed as the temperature at which the loss modulus G” has a maximum. The modulus of the rubbery plateau was determined at 40 °C above the Tg. The flow temperature (Tflow) was defined as the temperature where the storage modulus G’ reached 0.5 MPa. The crystallinity was estimated from the modulus in the rubbery plateau using the method described in.1,9 The effect crystalline of T6T6T content on the modulus of  PPE-T6T6T copolymers is comparable with that in PTMO-T6T6T.2,9  The estimated crystallinities are calculated with Eq. 1 and 2. BecrystallinTTTLogGG o *)(66'log' +=   (1) )(66)(66totalTTTecrystallinTTTX c =   (2) )(66*log'log 'totalTTTBGGX oc−=   (3)  G’o  is 1.3 MPa, B is 9.44.2,9   Differential Scanning Calorometry. DSC spectra were recorded on a Perkin Elmer DSC7 apparatus, equipped with a PE7700 computer and TAS-7 software, measured with a heating and cooling rate of 20 °C/min. The (peak) melting temperature and enthalpy were obtained from the second heating scan. The crystallisation temperature was defined as the maximum of the peak in the cooling scan.  Results and Discussion.  The bifunctional PPE telechelic with hydroxylic endgroups (PPE-2OH) was reacted with DPT and/or T6T6T-diphenyl. The used PPE-2OH had a number average molecular weight of 3500 g/mol and a Tg of 182 °C. Due to the aromatic nature and steric hindrance of the 2,6-dimethyl groups have the phenolic endgroups a low reactivity. Also present in PPE are Mannich base type OH-endgroups which are expected to have a very low reactivity too.11,13 In view of this was the final reaction step in the polymerization carried out at 280 °C.  The PPE-T6T6T/T copolymers from PPE-2OH and T6T6T-diphenyl copolymers were prepared with varying T6T6T content (11 - 0%). The T6T6T content was changed by replacing T6T6T-diphenyl units with DPT. The DPT forms a terephthalate (T) linkage between PPE segments (-PPE-T-PPE-). The copolymer without T6T6T is -PPE-T- and the copolymer without DPT is -PPE-T6T6T-. If both T6T6T and DPT are used the copolymer is abbreviated as -PPE-T6T6T/T-. The copolymers were obtained by a solution/melt polymerisation and had relative high inherent viscosities (0.31-0.38 dl/g) despite the low reactivity of the phenolic endgroups of PPE-2OH. Increasing the DPT content did not seem to have an effect on the inherent viscosities. The reactivity of the T6T6T-diphenyl is thus not lower than DPT and the miscibility of T6T6T-diphenyl with PPE-2OH not a problem. The copolymers were transparent. The melting behaviour of the copolymers was studied by DSC. As the T6T6T contents were low only measurable results could be obtained for the 11 wt% T6T6T copolymer. The melting temperature was at 261 °C and the crystallisation temperature at 222 °C. The Tm-Tc difference is 39 °C, which suggest a fast crystallisation but not very fast. For a very fast crystallisation Tm-Tc Proceedings Published 2007 by the American Chemical Societydifference should have been less than 30°C.2 The heats of melting and crystallisation were hardly measurable and were about 1 J/g.  The copolymers could be injection moulded into bars and these were tested by DMA (Fig. 2).  Figure 2. The storage (G’) and loss modulus (G”) as function of temperature as measured by DMA with different T6T6T contents : □ , 0 wt%; ○, 7 wt%; ♦, 9 wt%; ■, 10 wt%. The PPE-T copolymer (0 wt% T6T6T) is an amorphous material which is not expecting to crystallise. This copolymer had a Tg at 195 °C and a flow temperature (Tflow) of 220 °C. The Tg of the copolymer is thus higher than the prepolymer (182 °C) and this probably due to the increase in molecular weight. Increasing the T6T6T content decreased the Tg to 183 °C and increased the Tflow to 250-260 °C. As the Tg of the copolymers with T6T6T is lower than that of the amorphous copolymer PPE-T, some T6T6T units are expected to be mixed with the amorphous PPE phase. The flow temperature increased with T6T6T content due to crystallised T6T6T segments. The loss modulus (G”) of the PPE-T6T6T/T copolymers shows a shoulder at ~130°C that increased with T6T6T content. The shoulder in the loss modulus can be ascribed to the presence to an amorphous T6T6T phase. The crystallised T6T6T segments thus increased the dimensional stability of the copolymers and possibly also the solvent resistance. The shear storage modulus (G’) at 40 °C above Tg increased with T6T6T content to about 2 MPa. From the height of the storage modulus the T6T6T crystallinities can be estimated with Eq, 3. The copolymers with 9-11 wt% T6T6T had on average an estimated crystallinity of 20%. The non crystallized T6T6T segments were expected to be partly present the PPE phase as judged from the lowered Tg and partly as a separate T6T6T phase as judged from the shoulder in the loss modulus graph at 130 °C.    Conclusions  High molecular weight copolymers could be obtained from PPE-2OH and T6T6T-diphenyl. The phenolic terephthalate ester is apparently sufficient reactive for making these block copolymers. The amide concentration could be lowered by replacing some of the amide units by DPT. With T6T6T units the segments are mono disperse in length. The copolymers have a high Tg and a high melting temperature. The Tgs are somewhat lower that that of pure PPE (PPO-803) but higher than that of the starting prepolymer. The flow temperatures increase from 220 °C without T6T6T to 255-265 °C with 9-11 wt% -T6T6T-. The crystallinity of the amide segments in the studied copolymers is however not so high (~ 20%). Also the Tm-Tc is not so low, suggesting that the crystallization rate is not very fast. A part of the non crystalline T6T6T is present in the PPE phase and a part as an amorphous PA phase with a glass transition temperature of 130°C. The crystallinity in the copolymers can probably be improved by optimizing the molecular weight and the processing conditions. The properties of the -PPE-T6T6T- copolymers are fairly comparable and also with those of the copolymer with spacer units1-3, -PPE-T-spacer-T6T6T-spacer-T-. However, the crystallinities and the crystallization rates were higher with the -PPE-T-spacer-T6T6T-spacer-T-copolymer.   Acknowledgements.. This work was financially supported by the Dutch Polymer Institute (DPI, Eindhoven, the Netherlands) project #313. GE Plastics (Bergen op Zoom, the Netherlands) is acknowledged for providing the PPO-803®.   References (1) Krijgsman, J.; Feijen, J.; Gaymans, R.J. Polymer 2004, 45, 4677-4684. (2) Krijgsman, J.; Feijen, J.; Gaymans, R.J. Polymer 2004, 45, 4685-4692. (3) Krijgsman, J.; Gaymans, R.J. Polymer 2004, 45, 8523-8530. (4) Van Krevelen, D.W. Properties of Polymers, 3rd Ed.; Elsevier: Amsterdam, 1990; Chapter 19. (5) Bicerano, J. J. Macromol. Sci. 1998, C38, 391-479. (6) Niesten, M.C.E.J.; Gaymans, R.J. Polymer 2001, 42, 6199-6207.  (7) Zhu, L.; Wegner, G. Makromol. Chem. 1981, 182, 3625-3638. (8) Sauer, B.B.; McLean, R.S.; Thomas, R.R. Polym. Int. 2000, 49, 449-452.  (9) Krijgsman, J.; Husken, D.; Gaymans, R.J. Polymer 2003, 44, 7573-7588. (10) Krijgsman, J.; Biemond, G.J.E.; Gaymans, R.J. Polymer 2005, 46, 8250-8257. (11) Krijgsman, J.; Feijen, J.; Gaymans, R.J. Polymer 2003, 44, 7055-7065. (12) Krijgsman, J.; Husken, D.; Gaymans, R.J. Polymer 2003, 44, 7043-7053. (13) Chao, HS-I.; Whalen, J.M. Reactive Polymers 1991, 15, 9-23.  

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High Tg segmented copolymers with Monodisperse Crystallizable segments

High Tg segmented copolymers with Monodisperse Crystallizable segments

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