skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Controlled Synthesis and Properties of Poly( l -homoserine)
We report preparation of a new water soluble, non-ionic homopolypeptide poly(L-homoserine) as well as poly(L-homoserine) block copolymers with controllable segment lengths. The conformational preferences of poly(L-homoserine) were also determined in both the solid-state and in solution. Poly(L-homoserine) is soluble in water and adopts a disordered conformation that makes it a promising addition to the small class of non-ionic, water soluble homopolypeptides with potential for development for applications in biology. Toward this goal, a poly(L-homoserine) containing block copolypeptide was prepared and found to assemble into micro- and nanoscale vesicles in water.  more » « less
Award ID(s):
1904431
PAR ID:
10488931
Author(s) / Creator(s):
;
Publisher / Repository:
American Chemical Society
Date Published:
Journal Name:
ACS Macro Letters
Volume:
12
Issue:
4
ISSN:
2161-1653
Page Range / eLocation ID:
518 to 522
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Fundamental synthetic methodology was advanced to allow for the preparation of a reactive glucose-based block copolycarbonate, which was conveniently transformed into a series of amphiphilic block copolymers that underwent aqueous assembly into functional nanoparticle morphologies having practical utility in biomedical and other applications. Two degradable d -glucose carbonate monomers, with one carrying alkyne functionality, were designed and synthesized to access well-defined block polycarbonates ( Đ < 1.1) via sequential organocatalytic ring opening polymerizations (ROPs). Kinetic studies of the organocatalyzed sequential ROPs showed a linear relationship between the monomer conversion and the polymer molecular weight, which indicated the controlled fashion during each polymerization. The pendant alkyne groups underwent two classic click reactions, copper-catalyzed azide–alkyne dipolar cycloaddition (CuAAC) and thiol–yne addition reactions, which were employed to render hydrophilicity for the alkyne-containing block and to provide a variety of amphiphilic diblock poly( d -glucose carbonate)s (PGCs). The resulting amphiphilic PGCs were further assembled into a family of nanostructures with different sizes, morphologies, surface charges and functionalities. These non-ionic and anionic nanoparticles showed low cytotoxicity in RAW 264.7 mouse macrophage cells and MC3T3 healthy mouse osteoblast precursor cells, while the cationic nanoparticles exhibited significantly higher IC 50 (162 μg mL −1 in RAW 264.7; 199 μg mL −1 in MC3T3) compared to the commercially available cationic lipid-based formulation, Lipofectamine (IC 50 = 31 μg mL −1 ), making these nanomaterials of interest for biomedical applications. 
    more » « less
  2. 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. Abstract Two‐dimensional (2D) assemblies of water‐soluble block copolymers have been limited by a dearth of systematic studies that relate polymer structure to pathway mechanism and supramolecular morphology. Here, we employ sequence‐defined triblock DNA amphiphiles for the supramolecular polymerization of free‐standing DNA nanosheets in water. Our systematic modulation of amphiphile sequence shows the alkyl chain core forming a cell membrane‐like structure and the distal π‐stacking chromophore block folding back to interact with the hydrophilic DNA block on the nanosheet surface. This interaction is crucial to sheet formation, marked by a chiral “signature”, and sensitive to DNA sequence, where nanosheets form with a mixed sequence, but not with a homogeneous poly(thymine) sequence. This work opens the possibility of forming well‐ordered, bilayer‐like assemblies using a single DNA amphiphile for applications in cell sensing, nucleic acid therapeutic delivery and enzyme arrays. 
    more » « less
  4. Semicrystalline poly(l-lactide) (PLLA) is a leading biosourced, compostable alternative to conventional plastics but lacks sufficient toughness for many applications. Chain alignment via uniaxial stretching may be used to toughen PLLA but often creates anisotropic materials that are tough in the machine direction (MD) but brittle in the transverse direction (TD). This work reports uniaxially stretched films of PLLA blended with 3 wt % poly(ethylene oxide)-block-poly(butylene oxide) (PEO-PBO), which exhibit as much as a 5-fold increase in toughness in the TD compared to similarly stretched neat PLLA films─and elucidates the impact of PEO–PBO particles on the relationship between stretching, crystallization behavior, and resultant mechanical properties. Faster stretching rates were correlated with higher yield stress and a greater degree of crystallite alignment in the PEO–PBO/PLLA blends. This trend highlights the synergistic relationship between crystallinity and chain alignment and suggests a competing mechanism of heterogeneous crystallite nucleation around PEO–PBO particles. Importantly, PEO–PBO/PLLA exhibited a TD elongation at break of 36%, five times greater than the value of similarly stretched neat PLLA and even greater than the corresponding MD value of either material. Taken together, these findings demonstrate that uniaxial stretching of PEO–PBO/PLLA blends produces biaxially tough films, with the fastest stretching conditions producing the greatest enhancement in TD toughness. 
    more » « less
  5. The separation of oil from water and filtration of aqueous solutions and dispersions are critical issues in the processing of waste and contaminated water treatment. Membrane-based technology has been proven as an effective method for the separation of oil from water. In this research, novel vertical nanopores membrane, via oriented cylindrical block copolymer (BCP) films, suitable for oil/water filtration has been designed, fabricated and tested. We used a ∼100 nm thick model poly(styrene- block -methymethacrylate) (PS- b -PMMA) BCP as the active top nanofiltration layer, processed using a roll-to-roll (R2R) method of cold zone annealing (CZA) to obtain vertical orientation, followed by ultraviolet (UV) irradiation selective etch of PMMA cylinders to form vertically oriented nanopores as a novel feature compared to meandering nanopores in other reported BCP systems. The cylindrical nanochannels are hydrophilic, and have a uniform pore size (∼23 nm), a narrow pore size distribution and a high nanopore density (∼420 per sq. micron). The bottom supporting layer is a conventional microporous polyethersulfone (PES) membrane. The created asymmetric membrane is demonstrated to be effective for oil/water extraction with a modestly high throughput rate comparable to other RO/NF membranes. The molecular weight dependent filtration of a water soluble polymer, PEO, demonstrates the broader applications of such membranes. 
    more » « less