To simultaneously obtain outstanding stretchability, strength, and charge mobility of conjugated polymers (CPs) has remained a challenge for the field of stretchable electronics to date. Herein, we propose a strategy of increasing the molecular weight of a near-amorphous CP poly(indacenodithiophene-co-benzothiadiazole) (IDT-BT) to an ultrahigh level to overcome the trade-off. Detailed molecular weight-dependent study confirms that increasing the molecular weight can simultaneously enhance the mechanical and charge transport properties of IDT-BT, owing to the higher extent of chain entanglement and a larger range of charge transport along the backbone. Ultrahigh-molecular-weight (1049.6 kg mol −1 , weight average) IDT-BT exhibited the highest mobility of 2.63 cm 2 V −1 s −1 , modulus of 1126.7 MPa, elastic recovery >80%, crack onset strain >100%, fracture strain ≥20%, and a crack-free morphology after 100 cycles of strain. To the best of our knowledge, the ultrahigh-M w IDT-BT outperforms previously reported stretchable CPs by exhibiting enhanced elasticity, strength, and charge mobility at the same time.

Polymer semiconductors with large elastic recovery (ER) under high strain in thin film state are highly desirable for stretchable electronics. Here we report a type of stretchable semiconductor PU­(DPP) x , by copolymerization of oligodiketopyrrolopyrrole-based conjugated block and hydrogenated polybutadiene flexible block via urethane linkage for intermolecular hydrogen bonding. By regulating block ratio, PU­(DPP)35 with 35 wt % conjugated block exhibits high intrinsic ER > 80% under 175% strain (ε) in pseudo free-standing thin film state, comparable with commercial elastomers, and crack onset strain (COS) > 300% along with maximum hole mobility of 0.19 cm2 V–1 s–1 in organic thin film transistors to bring it to the best performing block copolymer-type stretchable semiconductors. Enhanced mobility is achieved using PU­(DPP)35 as the binder for conjugated polymer PDPPT3. The 25 wt %-PDPPT3 blend displays mobility up to 1.28 cm2 V–1 s–1 along with COS ∼120%, and 10 wt %-PDPPT3 blend exhibits ER of 78% at ε = 150%, COS of ∼230%, modulus of 36.5 MPa, maximum mobility of 0.62 cm2 V–1 s–1 and no obvious degradation of mobility at ε = 150% after 100 cycles of strain. Moreover, the structural similarity enables the blend film uniform and stable microstructure against mechanical and thermal deformation. Notably, PU­(DPP)35 and the blend are characterized by high mechanical performance similar to that of commercial elastomers in thin film state, and demonstrate their potential for high performance stretchable electronics.

The mutual effects of long-chain branch and ionic functional groups on polybutene-1 (PB-1) phase transition from tetragonal form II into hexagonal form I of polybutene-1 were investigated using differential scanning calorimetry and various thermal protocols. The novel butene-1/11-iodo-1-undecene (PB-IUD) copolymer was synthesized to incorporate the long-chain branches, and its iodine groups were reacted as the active sites to introduce ionic functional groups with BF 4 − , Tf 2 N − , and PF 6 − counterions. To the best of our knowledge, this is the first work to introduce physical ionic bonding into polybutene-1 (PB-1) ionomers and explore the affected phase transition. The results show that compared with the linear homopolymer, the long-chain branch largely retards the II−I phase transition of the PB-IUD copolymer. Unexpectedly, after introducing the ionic functional groups, ionomers have significantly accelerated transition with respect to reference PB-IUD, although they have exactly the same branching densities. This II−I phase transition of the ionomer can even happen at the crystallization temperature, where there is actually no cooling step to provide internal thermal stress. This indicates that additional crystallization-associated internal stress may be generated in ionomers for triggering form I nucleation. Moreover, the correlations of transition kinetics with annealing and crystallization temperatures were explored in depth. Ionomer phase transition can happen in a broad temperature range, which covers from the glass-transition temperature to high temperatures close to the melting region. Utilizing a stepwise annealing protocol, it was found that this broad transition temperature window originates from the persistent nucleation ability at elevated temperatures. On the other hand, ionomer transition kinetics increases with decreasing crystallization temperature, which, however, is opposite to that of the homopolymer. Based on this, a continuous cooling protocol was proposed and verified capable of endowing the branched ionomers with transition faster than the homopolymer.