01609nas a2200205   4500008004100000022001400041245004500055210004200100260007100142300001400213490000700227520095400234100002101188700002101209700002501230700002401255700002101279700002301300856008001323       2015                        eng d  a0024-929700aStar telechelic poly(L-lactide) ionomers0 aStar telechelic polyLlactide ionomers  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcSEP  a6580-65880 v483 a<p>Poly(L-lactide) (PLA), a biodegradable and biorenewable polymer, has many excellent properties that are equivalent to those of petroleum-derived plastics such as polystyrene, aromatic polyesters, etc. However, a major disadvantage of PLA which limits its processability is its poor melt elasticity. In this work we explore the possibility of improving the viscoelastic properties of PLA melt by incorporating ionic groups on the polymer. Specifically, we demonstrate the synthesis of star telechelic PLA anionomers by a three-step procedure involving synthesis of Star PIA, converting the hydroxyl end groups into carboxylic acid end groups, and finally converting these into ionic groups. Rheology data showed a dramatic increase in the elasticity of the star telechelic ionomer melts relative to the Star PLA melts. The viscoelasticity of star telechelic ionomers melts could be modulated by varying the number of ionic groups per molecule.</p>1 aKulkarni, Amruta1 aLele, Ashish, K.1 aSivaram, Swaminathan1 aRajamohanan, P., R.1 aVelankar, Sachin1 aChatterji, Apratim  uhttps://library.ncl.res.in/content/star-telechelic-polyl-lactide-ionomers-002123nas a2200193   4500008004100000245010300041210006900144260000800213300001600221490000700237520143400244100001801678700002001696700001401716700001701730700002301747700002701770856013201797       2021                        eng d00aRigidity dictates spontaneous helix formation of thermoresponsive colloidal chains in poor solvent0 aRigidity dictates spontaneous helix formation of thermoresponsiv  cDEC  a19702-197110 v153 aThe formation of helical motifs typically requires specific directional interactions. Here, we demonstrate that isotropic interparticle attraction can drive self-assembly of colloidal chains into thermo-reversible helices, for chains with a critical level of backbone rigidity. We prepare thermoresponsive colloidal chains by cross-linking PNIPAM microgel-coated polystyrene colloids (“monomers”), aligned in an AC electric field. We control the chain rigidity by varying cross-linking time. Above the LCST of PNIPAM, there is an effective attraction between monomers so that the colloidal chains are in a bad solvent. On heating, the chains decrease in size. For the most rigid chains, the decrease is modest and is not accompanied by a change in shape. Much less rigid chains form relatively compact structures, resulting in a large increase in the local monomer density. Unusually, chains with intermediate rigidity spontaneously assemble into helical structures. The chain helicity increases with temperature and plateaus above the collapse transition temperature of the microgel particles. We simulate a minimal model that captures the spontaneous emergence of the helical conformations of the polymeric chain and provides insight into this shape transition. Our work suggests that a purely mechanical instability for semiflexible filaments can drive helix formation, without the need to invoke directional interactions.1 aBiswas, Bipul1 aMitra, Debarshi1 aKP, Fayis1 aBhat, Suresh1 aChatterji, Apratim1 aKumaraswamy, Guruswamy  uhttps://library.ncl.res.in/content/rigidity-dictates-spontaneous-helix-formation-thermoresponsive-colloidal-chains-poor-solvent