Synthesis and characterization of a poly(methyl methacrylate-acrylic acid) copolymer for bioimplant applications

Abstract

SYNOPSISThis paper describes the development of a new crosslinked poly(methyl methacrylateacrylic acid) copolymer for potential applications in bone implants. This copolymer, comprising hydrophobic and hydrophilic components, has been designed to provide small amounts of controllable swelling strains at saturation when exposed to an aqueous saline environment. The volume fraction of the hydrophobic methyl methacrylate monomer to the hydrophilic acrylic acid monomer strongly influenced the swelling behavior of the copolymer. Two different cross-linking agents, allyl methacrylate and diethylene glycol dimethacrylate, were evaluated for their effectiveness in cross-linking and limiting the saturated swelling levels. The influences of the amounts of crosslinking agents and other processing parameters on the swelling behavior of the copolymer were studied using differential scanning calorimetry measurements, solubility tests, and swelling measurements in saline solutions. These measurements provided a good understanding of the structure of the copolymer, the effectiveness of the crosslinkers, the swelling mechanisms in this system, and the factors that strongly affect the swelling weight gain levels in this copolymer.

Development of self-anchoring bone implants. II. Bone-implant interface characteristicsin vitro

“…A smaller size implant and higher temperature, such as may be envisioned in an in vivo application, will drastically reduce the swelling time of the implant. Measurements of swelling characteristics of this copolymer at different temperatures 18 did indeed indicate that the saturated swelling strain in the copolymer and the swelling kinetics are both significantly enhanced by increasing temperature. For example, in free swelling conditions, the time to reach saturation at body temperature (37 ЊC) can be computed 18 to be about 0.58 times the time to reach saturation at 25 ЊC (roughly the ambient temperature in the experiments reported here).…”

“…Measurements of swelling characteristics of this copolymer at different temperatures 18 did indeed indicate that the saturated swelling strain in the copolymer and the swelling kinetics are both significantly enhanced by increasing temperature. For example, in free swelling conditions, the time to reach saturation at body temperature (37 ЊC) can be computed 18 to be about 0.58 times the time to reach saturation at 25 ЊC (roughly the ambient temperature in the experiments reported here). The mean and standard deviation (in parentheses) for the holding strength and holding stress are shown for the first push-out test conducted after 28 days of augmented with a temporary mechanism to provide short-terial achieve holding strength in bone comparable and often exceeding that of many conventional orthopedic fixa-term immediate fixation that will allow the bone anchor to swell and reach its full fixation capacity.…”

Fixation strength of swellable bone anchors in low-density polyurethane foam

“…Ratio of MMA/AA/ AMA monomers was 80/20/10, as established in our previous studies. 4 The amount of the initiator used was fixed to 0.4 g/100 mL of the total mixture. Polymerization was conducted in glass test tubes, which were tightly sealed and placed upright in a temperature-controlled water bath.…”

Preparation and characterization of crosslinked poly(methylmethacrylate‐acrylic acid sodium salt)‐modified bone cement

“…The swelling of the copolymer was constrained by the surrounding bone, and consequently, an interfacial pressure was developed at the bone–polymer interface. This interfacial pressure, in turn, increased the frictional resistance and improved significantly the fixation strength of the implants 6–11. Thus, crosslinked poly(MMA‐AA‐AMA)‐modified bone cement could compensate the shrinkage of bone cement during polymerization.…”