Method and Mathematical Modeling of Formation of Gradually and Homogeneously Oriented Linear Polymers

Previously, we developed several technical solutions for the conversion of isotropic polymers into materials of a new type—gradually oriented polymers with a gradient of physical and mechanical properties, thereby materializing for the first time the unused possibilities inherent in the polymeric nature of the substance. The scientific basis of these developments is the concept of a new structural state of linear polymers—a gradually oriented (stretched) state (GOS), the essence of which is set out briefly. An algorithm and a mathematical model for controlling the process of uniaxial, zonal stretching of linear polymers are proposed, which allow the formation of gradually or homogeneously oriented polymers (polymer composites). At the same time, specified values of quantitative parameters are ensured, in particular, the selected profile of distribution of the relative elongation (linear, sinusoidal, etc.) along the length of the gradually oriented polymer sample and the specified constant relative elongation along the length of the homogeneously oriented polymer. Mathematical expressions for calculating the conditions to obtain gradually oriented polymers with given geometric dimensions (length, width) and with a given distribution of relative elongation along the length of the resulting sample were also derived. The description of method and principles of operation of the appropriate device is given. Experimental data illustrating the possibilities of the proposed method and the efficiency of mathematical modeling are presented. The issues of creating functionally graded materials with a gradient of microstructure (gradient of degree of orientation/relative elongation) or chemical composition (volume fraction of functional fillers), respectively, based on thermoplastic polymer/copolymer or polymer composite (containing functional fillers) by method of uniaxial, zonal graded stretching are discussed.

Spider silk morphology for responsive materials

ABSTRACTThis study reveals that an “old” mechanism for shape memory in oriented polymers is in fact just one separate contribution for “supercontraction” in Nephila spider major ampulate silks. When Nephila spider silks are in contact with liquid water, they “super”-contract up to 28% of the original stretched length. However, we discovered that under glass transition conditions these silks only relax with a maximum shrinkage of 13%, and this phenomenon is defined as Tg-contraction. Structural components permanent order (PO), permanent disorder (PD), meta order (MO) and meta disorder (MD) were proposed from the primary amino-acid sequence of the silk protein to explain morphological changes in the two contraction phenomena: MD contributes 13% of the full supercontraction and contributes to Tg-contraction; whereas MO (the proline-containing motifs) contributes the rest for the full super-contraction and does not contribute to Tg-contraction. The morphology in Nephila spider silk structure suggests two separate mechanisms to generate the shape memory effect in synthetic polymers.