Process – structure – property relationships of erodable polymeric biomaterials: II—long range order in poly(desaminotyrosyl arylates) Michael Jaffe a, * , Zohar Ophir a , George Collins a , Ali Recber a , Seung-uk Yoo a , Joseph J. Rafalko b a Medical Device Concept Laboratory, Department of Biomedical Engineering, New Jersey Institute of Technology, 111 Lock Street, Newark, NJ 07103, USA b Ticona Inc., 86 Morris Avenue, Summit, NJ 07901, USA Received 8 April 2003; received in revised form 17 June 2003; accepted 17 June 2003 Dedicated to Prof. Ian M. Ward on the occasion of his 75th birthday Abstract The long-range order of some bioerodable polyesteramides based on a desaminotyrosyl [Thermochim Acta 396 (2003) 141; Polym Adv Technol 13 (2002) 926; J Am Chem Soc 119 (1997) 4553] diol monomer has been investigated. The order is mesogenic, best described as a ‘condis crystal’ or smectic-like. In all cases where long-range order is present, ordered H bonds between amide groups are observed. The order stabilizes the polymer to dimensional change and mechanical relaxation under biorelevant conditions. q 2003 Elsevier Ltd. All rights reserved. Keywords: Mesogenic bioerodable polyesteramide; FT-IR; Hydrogen bonding 1. Introduction In recent years, a broad range of synthetic, bioerodable polymers have been investigated as tissue engineering scaffolds or as materials to enable a variety of biomedical devices [1,2]. This literature is replete in papers dealing with the effects of various polymer chemistries and macro-architectures on cellular response but little work has been done to define the impact of polymer processing or morphology on the performance of these materials either with respect to cellular interactions or rate of property decay in vivo. Jaffe [3,4] has initiated a series of studies to define the impact of morphology and molecular orientation on the mechanical properties, dimensional stability, bioerosion rates and biological activity of erodable polymeric biomaterials. Current studies are focussed on the combinatorial library of Desaminotyr- osinetyrosyl (DT) containing polyarylates synthesized by Kohn [5,6]. The chemistry of the library matrix is shown in Fig. 1, while Fig. 2 shows a typical published library property, dry T g ; as a function of polymer molecular structure. Recently, Jaffe et al. [4] has shown these polymers to be unexpectedly richly structured, describing long-range order in compositions with aliphatic length in sidechain and diacid of at least eight (CH) 2 units, leading to the retention of process induced morphology under biorelevant conditions (aqueous, 37 8C), even though 37 8C is significantly higher than the reported T g [5]. In contrast, it has been shown that plasticization by water causes significant shrinkage and mechanical property loss (molecular relaxation) in molecularly oriented fibers of the short side-chain and short diacid variants of the poly(DTR,Y) library under similar conditions, although the reported dry T g ’s are significantly above 37 8C [6]. These results demonstrate the importance of morphology, and chain interactions on biorelevance performance. In this paper, the aspects of the novel long-range order observed in some compositions of the poly(DTR,Y) combinatorial library are examined by temperature and time dependent Fourier transform infra-red spectroscopy (FTIR), hot stage optical microscopy (OM) and thermally stimulated current analysis (TSC). The observed mesogenic order is clearly associated with the formation of ordered H bonds through the backbone amide linkage. Results are discussed in terms of the formation of the observed mesophases as well as the implications of the structure to in vivo polymer utility. 0032-3861/03/$ - see front matter q 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0032-3861(03)00559-7 Polymer 44 (2003) 6033–6042 www.elsevier.com/locate/polymer * Corresponding author. E-mail address: jaffe@adm.njit.edu (M. Jaffe).