Star‐Like Poly(N‐isopropylacrylamide) and Poly(ethylene glycol) Copolymers Self‐Arranged in Newfound Single Crystals and Associated Novel Class of Polymer Brush Regimes with V‐Type Tethers

Abstract

Linear poly(ethylene glycol) (PEG)‐block‐poly(N‐isopropylacrylamide) (PNIPAM) and star‐like three‐arm PEG‐star‐(PNIPAM)2 copolymers having one PEG and two PNIPAM blocks are synthesized by atom transfer radical polymerization (ATRP). Single crystals of these block copolymers are grown from amyl acetate and toluene dilute solutions. To recognize PNIPAM and PEG thicknesses, small angle X‐ray scattering (SAXS) is applied. V‐type brushes behave differently from linear brushes because doubly grafted PNIPAM blocks from a common point onto PEG substrate exert a higher osmotic pressure, leading to a thinner crystal. In addition to three ordinary regimes, a fourth or extremely stretched regime is detected for V‐type PNIPAM brushes. Although in PEG5000‐star‐(PNIPAM)2 single crystals with overall PNIPAM molecular weight of 37 000 g/mol, each PNIPAM arm is shorter than PNIPAM grafts in linear PEG5000‐block‐PNIPAM26000 single crystals, their switching point from second to third regime is significantly lower (22 vs 33 °C). The V‐type configuration of PNIPAM brushes cause them to be entered into the extremely stretched or fourth regime, which has not been previously detected for coily brushes. The boundary between third and fourth regimes for PEG5000‐star‐(PNIPAM)2 single crystals is verified at 31.5 and 23.5 °C in amyl acetate and toluene, respectively.

Chains Stiffness Effect on the Vertical Segregation of Mixed Polymer Brushes in Selective Solvent

“…One of the most widely used polymers that meet these conditions is Poly(N-isopropylacrylamide) (PNIPAAm). This temperature-sensitive polymer was used for the responsive brushes construction while combined with other macromolecules such as polystyrene (PS) [ 37 ], poly(acrylic acid) (PAA) [ 38 , 39 ], poly(ethylene glycol) (PEG) [ 40 , 41 ], or antimicrobial peptides [ 42 ]. PNIPAAm exhibits a lower critical solution temperature (LCST) close to the physiological temperature of humans (∼31 °C) [ 43 ], which makes its use in biomedical coatings promising.…”

Understanding Thermal Behavior of Poly(ethylene glycol)-block-poly(N-isopropylacrylamide) Hydrogel Using Two-Dimensional Correlation Infrared Spectroscopy

“…To overcome these shortcomings, there are many attempts to change the physical and chemical properties. 2,3,[5][6][7][8][9][10][11][12][13][14][15][16] Among them, attractive NiPAAm-based amphiphilic block copolymer, with a broad phase transition temperature range achieved by changing the molar fraction of poly(ethylene glycol) (PEG) or poly(ethylene oxide) (PEO), has been studied. 7,9,10,[13][14][15][16] Because PEG has many advantages, such as biocompatibility, biodegradability, and its resistance to both protein adsorption and cellular adhesion, 15,17,18 it can compensate the known weaknesses of PNiPAAm homopolymer through copolymerization.…”