Environmental, Health, and Legislation Considerations for Rational Design of Nonreactive Flame-Retardant Additives for Polymeric Materials: Future Perspectives.

Increasing polymer usage has demanded functional additives that decrease fire hazards for end users. While traditional flame-retardant (FR) additives, such as halogenated, phosphorus, and metal hydroxides, greatly reduce flammability and associated fire hazards, research has continually exposed a litany of health and environmental safety concerns. This perspective aims to identify the key components of a successful FR additive and address material, environmental, and health concerns of existing additives. Legislation surrounding FRs and persistent organic pollutants is also discussed to highlight political perception that has resulted in the increased chemical regulations and subsequent banning of FR additives. Finally, future directions of this field regarding nonreactive additives, focusing on the use of bioinspired materials and transition metal chemistries to produce alternatives for polymers with efficacies surpassing traditional additives are presented.

Supramolecular Assembly of Oriented Spherulitic Crystals of Conjugated Polymers Surrounding Carbon Nanotube Fibers.

The directed assembly of conjugated polymers into macroscopic organization with controlled orientation and placement is pivotal in improving device performance. Here, the supramolecular assembly of oriented spherulitic crystals of poly(3-butylthiophene) surrounding a single carbon nanotube fiber under controlled solvent evaporation of solution-cast films is reported. Oriented lamellar structures nucleate on the surface of the nanotube fiber in the form of a transcrystalline interphase. The factors influencing the formation of transcrystals are investigated in terms of chemical structure, crystallization temperature, and time. Dynamic process measurements exhibit the linear growth of transcrystals with time. Microstructural analysis of transcrystals reveals individual lamellar organization and crystal polymorphism. The form II modification occurs at low temperatures, while both form I and form II modifications coexist at high temperatures. A possible model is presented to interpret transcrystallization and polymorphism.