Developing Toughened Aromatic Polybenzoxazines Using Thermoplastic Oligomers and Telechelics, Part 1: Preparation and Characterization of the Functionalized Oligomers Ian Hamerton, 1 Lisa T. McNamara, 1 * Brendan J. Howlin, 1 Paul A. Smith, 2 Paul Cross, 3 Steven Ward 3 1 Faculty of Engineering and Physical Sciences, Department of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom 2 Faculty of Engineering and Physical Sciences, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom 3 Cytec, R414, Wilton Centre, Redcar, TS10 4RF, United Kingdom *Present address: Hexcel Composites, Duxford Cambridge CB22 4QD, United Kingdom Correspondence to: I. Hamerton (E - mail: i.hamerton@surrey.ac.uk) ABSTRACT: The preparation and characterization of three families of thermoplastic oligomers (M n 5 2918–13263 g mol 21 ) based on polyarylsulfone (PSU) differing in both molecular weight and terminal functionality and one series of polyarylethersulfone (PES) of different molecular weights is reported. Infrared and nuclear magnetic resonance spectroscopy data support the formation of both the hydroxyl terminated oligomers and conversion (67–89% depending on molecular weight) to the telechelic PSU oligomer bearing reactive benzoxazine groups. Differential scanning calorimetry reveals that the onset of homopolymerization in the telechelic PSU oligomer occurs at around 100  C (peak maximum 125  C at 10 K/min) and rescans show values of the glass transition (for the homo- polymers) ranging from 124 to 167  C depending on molecular weight. The influence on the oligomer backbone and terminal func- tionality is examined using thermal analysis. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40875. KEYWORDS: crosslinking; differential scanning calorimetry; thermal properties; thermoplastics; thermosets Received 17 February 2014; accepted 9 April 2014 DOI: 10.1002/app.40875 INTRODUCTION The potential for the use of oligomers based on engineering thermoplastics has been examined for some years e.g. as modi- fiers in aerospace composite matrices, 1,2 due to their inherent toughness and the ability to blend them more easily than high molecular weight species without incurring the penalty of high melt viscosity. 3 Poly(arylene ether sulfone)s are amongst the most widely reported high performance thermoplastics and were originally developed during the 1960s following inde- pendent research work by the 3M Corporation, 4 Union Car- bide, 5 and the Plastics Division of ICI 6 to develop thermally stable thermoplastics suitable for engineering applications; their chemistry has recently been reviewed. 7 The materials are highly aromatic polymers that comprise phenylene backbones bridged with heteroatoms (O, S) or groups (SO 2 , CH 2 , C(CH 3 ) 2 , etc.), to offer thermal stability, good mechanical properties, creep resistance, and chemical resistance. These polymers have now reached a degree of maturity with many variants having been reported in both laboratory and commercial publications, and have been reviewed extensively. 8 Commercial products (e.g., Udel V R , Radel V R , and VictrexV R ) are now available in a variety of grades to satisfy different high performance applications and widely used. Poly(arylene ether sulfone)s display a wide range of glass transition temperatures (T g ) influenced to a large degree by the chemical structure. 8 Hence, polymers produced from dichlorodiphenylsulfone and simple bisphenols yield high T g materials, typically in the range 180 to 230  C with the magnitude being influenced by the bulk of the substituents on the central carbon atom. The prediction of thermal and mechanical properties in as yet unsynthesized polymers is beginning to be realized and we have demonstrated this in a variety of thermosetting polymers such as epoxy resins, 9 cyanate esters, 10 and polybenzoxazines, 11 as well as engineering thermoplastics. 12,13 In a previous publi- cation, 14 we reported the use of a quantitative structure prop- erty relationship (QSPR) to predict the T g of a polymer of this type, but the model was severely limited by the size of the training set used to generate the QSPR equation. V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.40875 40875 (1 of 10)