More Like this

1. Nanoconfined Crystallization in Poly(lactic acid) (PLA) and Poly(ethylene terephthalate) (PET) Induced by Various Forms of Premelt‐Deformation

   https://doi.org/10.1002/marc.202200293  

   Smith, Travis; Feng, Jiansheng; Zou, Lu; Gao, Min; Prévôt, Marianne; Wang, Shi‐Qing (July 2022, Macromolecular Rapid Communications)

   Abstract The processing–structure–property relationship using poly(lactic acid) (PLA) and poly(ethylene terephthalate) (PET) is explored. Specifically, both pre‐extension and preshear of amorphous PLA and PET above their glass transition temperaturesT_g, carried out in the affine deformation limit, can induce a specific type of cold crystallization during annealing, i.e., nanoconfined crystallization (NCC) where crystal sizes are limited to a nanoscopic scale in all dimensions so as to render the processed PLA and PET optically transparent. The new polymer structure after premelt deformation can show considerably enhanced mechanical properties. For example, premelt stretching produces geometric condensation of the chain network. This structural alternation can profoundly change the mechanical characteristics, e.g., turning brittle PLA ductile. In contrast, after preshear of amorphous PLA aboveT_g, the NCC containing PLA remains brittle, showing the importance to have geometric condensation from processing. Both AFM imaging and SAXS measurements are performed to verify that premelt deformation of PLA and PET indeed results in NCC from annealing that permits the strain‐induced cold crystallization to take place on the length scale of the mesh size of the deformed chain network. 

   more » « less
2. Interfacial electrostatics of poly(vinylamine hydrochloride), poly(diallyldimethylammonium chloride), poly- l -lysine, and poly- l -arginine interacting with lipid bilayers

   https://doi.org/10.1039/C7CP07353D  

   McGeachy, A. C.; Dalchand, N.; Caudill, E. R.; Li, T.; Doğangün, M.; Olenick, L. L.; Chang, H.; Pedersen, J. A.; Geiger, F. M. (January 2018, Physical Chemistry Chemical Physics)

   Charge densities of cationic polymers adsorbed to lipid bilayers are estimated from second harmonic generation (SHG) spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) measurements. The systems surveyed included poly(vinylamine hydrochloride) (PVAm), poly(diallyldimethylammonium chloride) (PDADMAC), poly- l -lysine (PLL), and poly- l -arginine (PLR), as well as polyalcohol controls. Upon accounting for the number of positive charges associated with each polyelectrolyte, the binding constants and apparent free energies of adsorption as estimated from SHG data are comparable despite differences in molecular masses and molecular structure, with Δ G ads values of −61 ± 2, −58 ± 2, −57 ± 1, −52 ± 2, −52 ± 1 kJ mol −1 for PDADMAC 400 , PDADMAC 100 , PVAm, PLL, and PLR, respectively. Moreover, we find charge densities for polymer adlayers of approximately 0.3 C m −2 for poly(diallyldimethylammonium chloride) while those of poly(vinylamine) hydrochloride, poly- l -lysine, and poly- l -arginine are approximately 0.2 C m −2 . Time-dependent studies indicate that polycation adsorption to supported lipid bilayers is only partially reversible for most of the polymers explored. Poly(diallyldimethylammonium chloride) does not demonstrate reversible binding even over long timescales (>8 hours). 

   more » « less
3. Ethyl cellulose- block -poly(benzyl glutamate) block copolymer compatibilizers for ethyl cellulose/poly(ethylene terephthalate) blends

   https://doi.org/10.1039/D4PY00688G  

   Chinn, Abigail F; Trindade_Coutinho, Isabela; Kethireddy, Saipranavi Reddy; Williams, Noah R; Knott, Kenneth M; Moore, Robert B; Matson, John B (August 2024, Polymer Chemistry)

   Luscombe, Christine; Anastasaki, Athina; Du_Prez, Filip; Frey, Holger; Hu, Rongrong; Klausen, Rebekka; Konkolewicz; Li, Zhibo; Li, Zi_Chen; Sardon, Haritz (Ed.)

   A block copolymer with the structure ethylcellulose-block-poly(benzy glutamate) was synthesizedviaring-opening polymerization and used as a compatibilizer to produce blends of ethylcellulose and poly(ethylene terephthalate). 

   more » « less
4. Dynamics of poly(methyl acrylate)/poly(methyl methacrylate)-grafted-Fe ₃ O ₄ nanocomposites

   https://doi.org/10.1039/D4SM00731j  

   Patil, Shalin; Mbonu, Christopher; Chou, Tsengming; Li, Ruhao; Wu, Di; Akcora, Pinar; Cheng, Shiwang (October 2024, Soft Matter)

   Nie, Zhihong (Ed.)

   Immiscible blends of poly(methyl acrylate) (PMA) and poly(methyl methacrylate) (PMMA) exhibit component dynamics and dynamics confinement effect at the PMA/PMMA-g-Fe₃O₄interface, suggesting new routes to control interface dynamics. 

   more » « less
5. Hydrolytic crack growth and embrittlement in poly(ethylene terephthalate)

   https://doi.org/10.1016/j.jmps.2023.105303  

   Kadoma, Atte; Jiao, Quan; Vlassak, Joost J.; Suo, Zhigang (July 2023, Journal of the Mechanics and Physics of Solids)

   Poly(ethyleneterephthalate)(PET)is ather moplastic of high-volu me applications, andisiden- tified as Nu mber 1inthe ResinIdentification Code onsingle-use packages. The ester bondsinthe poly mer chains are prone to hydrolysis, but the rate of hydrolysis is extre mely lo w at roo m temperature. Here weshowthathydrolysiscausesPETtogrowcracksevenatroomtemperature and under lo w loads. The hydrolytic cracks greatly outrun erosion. When PET is sub merged in water andsubjectedto a fixedload,the crack velocityincreases with p H. At highloads,the crack gro ws rapidly, and hydrolysis is negligible, so that the crack gro ws with substantial plastic defor mation andthefracturesurfaceisrough. Atlo wloads,the crack gro wsslo wly and hydrolysis isfastenough,sothatthecrackgrows withnegligibleplasticdeformationandthefracturesurface is s mooth. These observations sho w that hydrolysis e mbrittles PET. Under develop ment for sus- tainability and healthcare are biodegradable and bio mass-derived poly mers, many of which have hydrolysablegroupsinthe mainchainsorcrosslinks.Theyareallpotentiallysusceptibletohy- drolyticcrackgrowthandembrittlement.Itishopedthatthisstudy willaidthedevelopmentand applications ofthese poly mers. 

   more » « less