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The preparation of aromatic macromonomers with hydroxyl functions was achieved by termination of living polystyrene (PSLi) upon addition of 2,5-dimethoxybenzyl bromide (2) or l,l-bis(4-methoxyphenyl)ethylene (16). Ether cleavage with boron tribromide resulted in the formation of the de-protected macromonomers 15 and 17. Side reactions occurring in the functionalisation reaction with 2 were investigated by means of @ respective model reaction. The formation of side products could be suppressed by reacting PSLi with 1,l-diphenylethylene prior to functionalisation with 2. The macromonomers were characterized by GPC, UV, and FT-IR spectroscopy.

Liquid-crystalline main-chain polyesters with polystyrene side chains of different length and number per main chain were synthesized using aromatic hydroxyfunctional polystyrene (PS) macromonomers, terephthalic acid derivatives and tert-butylhydroquinone as co-diol. The molecular weight of the polystyrene side chain was varied in the range from 1000 to 20000. The influence of this novel type of substituent on the solubility, thermal behaviour and miscibility with PS as a flexible matrix polymer is discussed. The properties of the new compounds are compared to those of the respective homopolyester. The graft copolyesters are, depending on the characteristics of the polymeric substituent, soluble in common organic solvents and their thermal transition points are lowered compared to the homopolyester. Compared to blends of the homopolyester, the improvement of miscibility of the polymer-substituted rigid rods with PS as an example for a flexible matrix polymer can be valued as a step to molecular reinforcement.

The fracture response of injection molded short glass fiber (GF) reinforced and rubber‐toughened poly(butylene terephthalate) (PBT) composites has been characterized by the fracture toughness (Kc) and energy (Gc), measured on static‐loaded compact tension (CT) specimens. The related failure of the composites with 30 wt% GF reinforcement in as‐received (AR), hygrothermally aged (HA) and re‐dried (RD) states, respectively, was studied by acoustic emission (AE) and fractography. Tougheners were functionalized ethylene/acrylate (EAF), crosslinked acrylate (XAR) and core‐shell type (CSR) rubbers, at 20 wt% in the composites. It was shown that both Kc and Gc decrease with hygrothermal aging at 90°C, and their values cannot be restored by subsequent drying. This is attributed to severe hydrolysis degradation of the PBT matrix. Deterioration in the fracture parameters was affected by the composition of the rubbery toughener: The toughness retention by EAF was superior to the other modifiers. The difference in the failure mode of the GF‐PBT composites before and after hygrothermal aging was revealed by viewing the fracture surface of the CT‐specimens in scanning electron microscope (SEM). Based on the fractographic results, changes in the AE amplitude envelopes are interpreted and discussed.

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